13 Feb, 2019
1 commit
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This reverts commit 172b06c32b9497 ("mm: slowly shrink slabs with a
relatively small number of objects").This change changes the agressiveness of shrinker reclaim, causing small
cache and low priority reclaim to greatly increase scanning pressure on
small caches. As a result, light memory pressure has a disproportionate
affect on small caches, and causes large caches to be reclaimed much
faster than previously.As a result, it greatly perturbs the delicate balance of the VFS caches
(dentry/inode vs file page cache) such that the inode/dentry caches are
reclaimed much, much faster than the page cache and this drives us into
several other caching imbalance related problems.As such, this is a bad change and needs to be reverted.
[ Needs some massaging to retain the later seekless shrinker
modifications.]Link: http://lkml.kernel.org/r/20190130041707.27750-3-david@fromorbit.com
Fixes: 172b06c32b9497 ("mm: slowly shrink slabs with a relatively small number of objects")
Signed-off-by: Dave Chinner
Cc: Wolfgang Walter
Cc: Roman Gushchin
Cc: Spock
Cc: Rik van Riel
Cc: Michal Hocko
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
29 Dec, 2018
2 commits
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Waiting on a page migration entry has used wait_on_page_locked() all along
since 2006: but you cannot safely wait_on_page_locked() without holding a
reference to the page, and that extra reference is enough to make
migrate_page_move_mapping() fail with -EAGAIN, when a racing task faults
on the entry before migrate_page_move_mapping() gets there.And that failure is retried nine times, amplifying the pain when trying to
migrate a popular page. With a single persistent faulter, migration
sometimes succeeds; with two or three concurrent faulters, success becomes
much less likely (and the more the page was mapped, the worse the overhead
of unmapping and remapping it on each try).This is especially a problem for memory offlining, where the outer level
retries forever (or until terminated from userspace), because a heavy
refault workload can trigger an endless loop of migration failures.
wait_on_page_locked() is the wrong tool for the job.David Herrmann (but was he the first?) noticed this issue in 2014:
https://marc.info/?l=linux-mm&m=140110465608116&w=2Tim Chen started a thread in August 2017 which appears relevant:
https://marc.info/?l=linux-mm&m=150275941014915&w=2 where Kan Liang went
on to implicate __migration_entry_wait():
https://marc.info/?l=linux-mm&m=150300268411980&w=2 and the thread ended
up with the v4.14 commits: 2554db916586 ("sched/wait: Break up long wake
list walk") 11a19c7b099f ("sched/wait: Introduce wakeup boomark in
wake_up_page_bit")Baoquan He reported "Memory hotplug softlock issue" 14 November 2018:
https://marc.info/?l=linux-mm&m=154217936431300&w=2We have all assumed that it is essential to hold a page reference while
waiting on a page lock: partly to guarantee that there is still a struct
page when MEMORY_HOTREMOVE is configured, but also to protect against
reuse of the struct page going to someone who then holds the page locked
indefinitely, when the waiter can reasonably expect timely unlocking.But in fact, so long as wait_on_page_bit_common() does the put_page(), and
is careful not to rely on struct page contents thereafter, there is no
need to hold a reference to the page while waiting on it. That does mean
that this case cannot go back through the loop: but that's fine for the
page migration case, and even if used more widely, is limited by the "Stop
walking if it's locked" optimization in wake_page_function().Add interface put_and_wait_on_page_locked() to do this, using "behavior"
enum in place of "lock" arg to wait_on_page_bit_common() to implement it.
No interruptible or killable variant needed yet, but they might follow: I
have a vague notion that reporting -EINTR should take precedence over
return from wait_on_page_bit_common() without knowing the page state, so
arrange it accordingly - but that may be nothing but pedantic.__migration_entry_wait() still has to take a brief reference to the page,
prior to calling put_and_wait_on_page_locked(): but now that it is dropped
before waiting, the chance of impeding page migration is very much
reduced. Should we perhaps disable preemption across this?shrink_page_list()'s __ClearPageLocked(): that was a surprise! This
survived a lot of testing before that showed up. PageWaiters may have
been set by wait_on_page_bit_common(), and the reference dropped, just
before shrink_page_list() succeeds in freezing its last page reference: in
such a case, unlock_page() must be used. Follow the suggestion from
Michal Hocko, just revert a978d6f52106 ("mm: unlockless reclaim") now:
that optimization predates PageWaiters, and won't buy much these days; but
we can reinstate it for the !PageWaiters case if anyone notices.It does raise the question: should vmscan.c's is_page_cache_freeable() and
__remove_mapping() now treat a PageWaiters page as if an extra reference
were held? Perhaps, but I don't think it matters much, since
shrink_page_list() already had to win its trylock_page(), so waiters are
not very common there: I noticed no difference when trying the bigger
change, and it's surely not needed while put_and_wait_on_page_locked() is
only used for page migration.[willy@infradead.org: add put_and_wait_on_page_locked() kerneldoc]
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261121330.1116@eggly.anvils
Signed-off-by: Hugh Dickins
Reported-by: Baoquan He
Tested-by: Baoquan He
Reviewed-by: Andrea Arcangeli
Acked-by: Michal Hocko
Acked-by: Linus Torvalds
Acked-by: Vlastimil Babka
Cc: Matthew Wilcox
Cc: Baoquan He
Cc: David Hildenbrand
Cc: Mel Gorman
Cc: David Herrmann
Cc: Tim Chen
Cc: Kan Liang
Cc: Andi Kleen
Cc: Davidlohr Bueso
Cc: Peter Zijlstra
Cc: Christoph Lameter
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
An external fragmentation event was previously described as
When the page allocator fragments memory, it records the event using
the mm_page_alloc_extfrag event. If the fallback_order is smaller
than a pageblock order (order-9 on 64-bit x86) then it's considered
an event that will cause external fragmentation issues in the future.The kernel reduces the probability of such events by increasing the
watermark sizes by calling set_recommended_min_free_kbytes early in the
lifetime of the system. This works reasonably well in general but if
there are enough sparsely populated pageblocks then the problem can still
occur as enough memory is free overall and kswapd stays asleep.This patch introduces a watermark_boost_factor sysctl that allows a zone
watermark to be temporarily boosted when an external fragmentation causing
events occurs. The boosting will stall allocations that would decrease
free memory below the boosted low watermark and kswapd is woken if the
calling context allows to reclaim an amount of memory relative to the size
of the high watermark and the watermark_boost_factor until the boost is
cleared. When kswapd finishes, it wakes kcompactd at the pageblock order
to clean some of the pageblocks that may have been affected by the
fragmentation event. kswapd avoids any writeback, slab shrinkage and swap
from reclaim context during this operation to avoid excessive system
disruption in the name of fragmentation avoidance. Care is taken so that
kswapd will do normal reclaim work if the system is really low on memory.This was evaluated using the same workloads as "mm, page_alloc: Spread
allocations across zones before introducing fragmentation".1-socket Skylake machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 1 THP allocating thread
--------------------------------------4.20-rc3 extfrag events < order 9: 804694
4.20-rc3+patch: 408912 (49% reduction)
4.20-rc3+patch1-4: 18421 (98% reduction)4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-1 653.58 ( 0.00%) 652.71 ( 0.13%)
Amean fault-huge-1 0.00 ( 0.00%) 178.93 * -99.00%*4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-1 0.00 ( 0.00%) 5.12 ( 100.00%)Note that external fragmentation causing events are massively reduced by
this path whether in comparison to the previous kernel or the vanilla
kernel. The fault latency for huge pages appears to be increased but that
is only because THP allocations were successful with the patch applied.1-socket Skylake machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------4.20-rc3 extfrag events < order 9: 291392
4.20-rc3+patch: 191187 (34% reduction)
4.20-rc3+patch1-4: 13464 (95% reduction)thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Min fault-base-1 912.00 ( 0.00%) 905.00 ( 0.77%)
Min fault-huge-1 127.00 ( 0.00%) 135.00 ( -6.30%)
Amean fault-base-1 1467.55 ( 0.00%) 1481.67 ( -0.96%)
Amean fault-huge-1 1127.11 ( 0.00%) 1063.88 * 5.61%*4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-1 77.64 ( 0.00%) 83.46 ( 7.49%)As before, massive reduction in external fragmentation events, some jitter
on latencies and an increase in THP allocation success rates.2-socket Haswell machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 5 THP allocating threads
----------------------------------------------------------------4.20-rc3 extfrag events < order 9: 215698
4.20-rc3+patch: 200210 (7% reduction)
4.20-rc3+patch1-4: 14263 (93% reduction)4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-5 1346.45 ( 0.00%) 1306.87 ( 2.94%)
Amean fault-huge-5 3418.60 ( 0.00%) 1348.94 ( 60.54%)4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-5 0.78 ( 0.00%) 7.91 ( 910.64%)There is a 93% reduction in fragmentation causing events, there is a big
reduction in the huge page fault latency and allocation success rate is
higher.2-socket Haswell machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------4.20-rc3 extfrag events < order 9: 166352
4.20-rc3+patch: 147463 (11% reduction)
4.20-rc3+patch1-4: 11095 (93% reduction)thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-5 6217.43 ( 0.00%) 7419.67 * -19.34%*
Amean fault-huge-5 3163.33 ( 0.00%) 3263.80 ( -3.18%)4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-5 95.14 ( 0.00%) 87.98 ( -7.53%)There is a large reduction in fragmentation events with some jitter around
the latencies and success rates. As before, the high THP allocation
success rate does mean the system is under a lot of pressure. However, as
the fragmentation events are reduced, it would be expected that the
long-term allocation success rate would be higher.Link: http://lkml.kernel.org/r/20181123114528.28802-5-mgorman@techsingularity.net
Signed-off-by: Mel Gorman
Acked-by: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: David Rientjes
Cc: Michal Hocko
Cc: Zi Yan
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
20 Nov, 2018
1 commit
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Pull in v4.20-rc3 via drm-next.
Signed-off-by: Jani Nikula
07 Nov, 2018
1 commit
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The i915 driver uses shmemfs to allocate backing storage for gem
objects. These shmemfs pages can be pinned (increased ref count) by
shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
wastes a lot of time scanning these pinned pages. In some extreme case,
all pages in the inactive anon lru are pinned, and only the inactive
anon lru is scanned due to inactive_ratio, the system cannot swap and
invokes the oom-killer. Mark these pinned pages as unevictable to speed
up vmscan.Export pagevec API check_move_unevictable_pages().
This patch was inspired by Chris Wilson's change [1].
[1]: https://patchwork.kernel.org/patch/9768741/
Cc: Chris Wilson
Cc: Joonas Lahtinen
Cc: Peter Zijlstra
Cc: Andrew Morton
Cc: Dave Hansen
Signed-off-by: Kuo-Hsin Yang
Acked-by: Michal Hocko # mm part
Reviewed-by: Chris Wilson
Acked-by: Dave Hansen
Acked-by: Andrew Morton
Link: https://patchwork.freedesktop.org/patch/msgid/20181106132324.17390-1-chris@chris-wilson.co.uk
Signed-off-by: Chris Wilson
29 Oct, 2018
1 commit
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Pull XArray conversion from Matthew Wilcox:
"The XArray provides an improved interface to the radix tree data
structure, providing locking as part of the API, specifying GFP flags
at allocation time, eliminating preloading, less re-walking the tree,
more efficient iterations and not exposing RCU-protected pointers to
its users.This patch set
1. Introduces the XArray implementation
2. Converts the pagecache to use it
3. Converts memremap to use it
The page cache is the most complex and important user of the radix
tree, so converting it was most important. Converting the memremap
code removes the only other user of the multiorder code, which allows
us to remove the radix tree code that supported it.I have 40+ followup patches to convert many other users of the radix
tree over to the XArray, but I'd like to get this part in first. The
other conversions haven't been in linux-next and aren't suitable for
applying yet, but you can see them in the xarray-conv branch if you're
interested"* 'xarray' of git://git.infradead.org/users/willy/linux-dax: (90 commits)
radix tree: Remove multiorder support
radix tree test: Convert multiorder tests to XArray
radix tree tests: Convert item_delete_rcu to XArray
radix tree tests: Convert item_kill_tree to XArray
radix tree tests: Move item_insert_order
radix tree test suite: Remove multiorder benchmarking
radix tree test suite: Remove __item_insert
memremap: Convert to XArray
xarray: Add range store functionality
xarray: Move multiorder_check to in-kernel tests
xarray: Move multiorder_shrink to kernel tests
xarray: Move multiorder account test in-kernel
radix tree test suite: Convert iteration test to XArray
radix tree test suite: Convert tag_tagged_items to XArray
radix tree: Remove radix_tree_clear_tags
radix tree: Remove radix_tree_maybe_preload_order
radix tree: Remove split/join code
radix tree: Remove radix_tree_update_node_t
page cache: Finish XArray conversion
dax: Convert page fault handlers to XArray
...
27 Oct, 2018
4 commits
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The page cache and most shrinkable slab caches hold data that has been
read from disk, but there are some caches that only cache CPU work, such
as the dentry and inode caches of procfs and sysfs, as well as the subset
of radix tree nodes that track non-resident page cache.Currently, all these are shrunk at the same rate: using DEFAULT_SEEKS for
the shrinker's seeks setting tells the reclaim algorithm that for every
two page cache pages scanned it should scan one slab object.This is a bogus setting. A virtual inode that required no IO to create is
not twice as valuable as a page cache page; shadow cache entries with
eviction distances beyond the size of memory aren't either.In most cases, the behavior in practice is still fine. Such virtual
caches don't tend to grow and assert themselves aggressively, and usually
get picked up before they cause problems. But there are scenarios where
that's not true.Our database workloads suffer from two of those. For one, their file
workingset is several times bigger than available memory, which has the
kernel aggressively create shadow page cache entries for the non-resident
parts of it. The workingset code does tell the VM that most of these are
expendable, but the VM ends up balancing them 2:1 to cache pages as per
the seeks setting. This is a huge waste of memory.These workloads also deal with tens of thousands of open files and use
/proc for introspection, which ends up growing the proc_inode_cache to
absurdly large sizes - again at the cost of valuable cache space, which
isn't a reasonable trade-off, given that proc inodes can be re-created
without involving the disk.This patch implements a "zero-seek" setting for shrinkers that results in
a target ratio of 0:1 between their objects and IO-backed caches. This
allows such virtual caches to grow when memory is available (they do
cache/avoid CPU work after all), but effectively disables them as soon as
IO-backed objects are under pressure.It then switches the shrinkers for procfs and sysfs metadata, as well as
excess page cache shadow nodes, to the new zero-seek setting.Link: http://lkml.kernel.org/r/20181009184732.762-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner
Reported-by: Domas Mituzas
Reviewed-by: Andrew Morton
Reviewed-by: Rik van Riel
Acked-by: Peter Zijlstra (Intel)
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When systems are overcommitted and resources become contended, it's hard
to tell exactly the impact this has on workload productivity, or how close
the system is to lockups and OOM kills. In particular, when machines work
multiple jobs concurrently, the impact of overcommit in terms of latency
and throughput on the individual job can be enormous.In order to maximize hardware utilization without sacrificing individual
job health or risk complete machine lockups, this patch implements a way
to quantify resource pressure in the system.A kernel built with CONFIG_PSI=y creates files in /proc/pressure/ that
expose the percentage of time the system is stalled on CPU, memory, or IO,
respectively. Stall states are aggregate versions of the per-task delay
accounting delays:cpu: some tasks are runnable but not executing on a CPU
memory: tasks are reclaiming, or waiting for swapin or thrashing cache
io: tasks are waiting for io completionsThese percentages of walltime can be thought of as pressure percentages,
and they give a general sense of system health and productivity loss
incurred by resource overcommit. They can also indicate when the system
is approaching lockup scenarios and OOMs.To do this, psi keeps track of the task states associated with each CPU
and samples the time they spend in stall states. Every 2 seconds, the
samples are averaged across CPUs - weighted by the CPUs' non-idle time to
eliminate artifacts from unused CPUs - and translated into percentages of
walltime. A running average of those percentages is maintained over 10s,
1m, and 5m periods (similar to the loadaverage).[hannes@cmpxchg.org: doc fixlet, per Randy]
Link: http://lkml.kernel.org/r/20180828205625.GA14030@cmpxchg.org
[hannes@cmpxchg.org: code optimization]
Link: http://lkml.kernel.org/r/20180907175015.GA8479@cmpxchg.org
[hannes@cmpxchg.org: rename psi_clock() to psi_update_work(), per Peter]
Link: http://lkml.kernel.org/r/20180907145404.GB11088@cmpxchg.org
[hannes@cmpxchg.org: fix build]
Link: http://lkml.kernel.org/r/20180913014222.GA2370@cmpxchg.org
Link: http://lkml.kernel.org/r/20180828172258.3185-9-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner
Acked-by: Peter Zijlstra (Intel)
Tested-by: Daniel Drake
Tested-by: Suren Baghdasaryan
Cc: Christopher Lameter
Cc: Ingo Molnar
Cc: Johannes Weiner
Cc: Mike Galbraith
Cc: Peter Enderborg
Cc: Randy Dunlap
Cc: Shakeel Butt
Cc: Tejun Heo
Cc: Vinayak Menon
Cc: Randy Dunlap
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Refaults happen during transitions between workingsets as well as in-place
thrashing. Knowing the difference between the two has a range of
applications, including measuring the impact of memory shortage on the
system performance, as well as the ability to smarter balance pressure
between the filesystem cache and the swap-backed workingset.During workingset transitions, inactive cache refaults and pushes out
established active cache. When that active cache isn't stale, however,
and also ends up refaulting, that's bonafide thrashing.Introduce a new page flag that tells on eviction whether the page has been
active or not in its lifetime. This bit is then stored in the shadow
entry, to classify refaults as transitioning or thrashing.How many page->flags does this leave us with on 32-bit?
20 bits are always page flags
21 if you have an MMU
23 with the zone bits for DMA, Normal, HighMem, Movable
29 with the sparsemem section bits
30 if PAE is enabled
31 with this patch.
So on 32-bit PAE, that leaves 1 bit for distinguishing two NUMA nodes. If
that's not enough, the system can switch to discontigmem and re-gain the 6
or 7 sparsemem section bits.Link: http://lkml.kernel.org/r/20180828172258.3185-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner
Acked-by: Peter Zijlstra (Intel)
Tested-by: Daniel Drake
Tested-by: Suren Baghdasaryan
Cc: Christopher Lameter
Cc: Ingo Molnar
Cc: Johannes Weiner
Cc: Mike Galbraith
Cc: Peter Enderborg
Cc: Randy Dunlap
Cc: Shakeel Butt
Cc: Tejun Heo
Cc: Vinayak Menon
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
I've noticed, that dying memory cgroups are often pinned in memory by a
single pagecache page. Even under moderate memory pressure they sometimes
stayed in such state for a long time. That looked strange.My investigation showed that the problem is caused by applying the LRU
pressure balancing math:scan = div64_u64(scan * fraction[lru], denominator),
where
denominator = fraction[anon] + fraction[file] + 1.
Because fraction[lru] is always less than denominator, if the initial scan
size is 1, the result is always 0.This means the last page is not scanned and has
no chances to be reclaimed.Fix this by rounding up the result of the division.
In practice this change significantly improves the speed of dying cgroups
reclaim.[guro@fb.com: prevent double calculation of DIV64_U64_ROUND_UP() arguments]
Link: http://lkml.kernel.org/r/20180829213311.GA13501@castle
Link: http://lkml.kernel.org/r/20180827162621.30187-3-guro@fb.com
Signed-off-by: Roman Gushchin
Reviewed-by: Andrew Morton
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Tejun Heo
Cc: Rik van Riel
Cc: Konstantin Khlebnikov
Cc: Matthew Wilcox
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
21 Oct, 2018
2 commits
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This is just a variable rename and comment change.
Signed-off-by: Matthew Wilcox
-
Both callers of __delete_from_swap_cache have the swp_entry_t already,
so pass that in to make constructing the XA_STATE easier.Signed-off-by: Matthew Wilcox
06 Oct, 2018
1 commit
-
do_shrink_slab() returns unsigned long value, and the placing into int
variable cuts high bytes off. Then we compare ret and 0xfffffffe (since
SHRINK_EMPTY is converted to ret type).Thus a large number of objects returned by do_shrink_slab() may be
interpreted as SHRINK_EMPTY, if low bytes of their value are equal to
0xfffffffe. Fix that by declaration ret as unsigned long in these
functions.Link: http://lkml.kernel.org/r/153813407177.17544.14888305435570723973.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Reported-by: Cyrill Gorcunov
Acked-by: Cyrill Gorcunov
Reviewed-by: Josef Bacik
Cc: Michal Hocko
Cc: Andrey Ryabinin
Cc: Johannes Weiner
Cc: Tetsuo Handa
Cc: Shakeel Butt
Signed-off-by: Andrew Morton
Signed-off-by: Greg Kroah-Hartman
21 Sep, 2018
1 commit
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9092c71bb724 ("mm: use sc->priority for slab shrink targets") changed the
way that the target slab pressure is calculated and made it
priority-based:delta = freeable >> priority;
delta *= 4;
do_div(delta, shrinker->seeks);The problem is that on a default priority (which is 12) no pressure is
applied at all, if the number of potentially reclaimable objects is less
than 4096 (1<
Acked-by: Rik van Riel
Cc: Josef Bacik
Cc: Johannes Weiner
Cc: Shakeel Butt
Cc: Michal Hocko
Cc: Vladimir Davydov
Signed-off-by: Andrew Morton
Signed-off-by: Greg Kroah-Hartman
23 Aug, 2018
2 commits
-
page_freeze_refs/page_unfreeze_refs have already been relplaced by
page_ref_freeze/page_ref_unfreeze , but they are not modified in the
comments.Link: http://lkml.kernel.org/r/1532590226-106038-1-git-send-email-jiang.biao2@zte.com.cn
Signed-off-by: Jiang Biao
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There is a sad BUG introduced in patch adding SHRINKER_REGISTERING.
shrinker_idr business is only for memcg-aware shrinkers. Only such type
of shrinkers have id and they must be finaly installed via idr_replace()
in this function. For !memcg-aware shrinkers we never initialize
shrinker->id field.But there are all types of shrinkers passed to idr_replace(), and every
!memcg-aware shrinker with random ID (most probably, its id is 0)
replaces memcg-aware shrinker pointed by the ID in IDR.This patch fixes the problem.
Link: http://lkml.kernel.org/r/8ff8a793-8211-713a-4ed9-d6e52390c2fc@virtuozzo.com
Fixes: 7e010df53c80 "mm: use special value SHRINKER_REGISTERING instead of list_empty() check"
Signed-off-by: Kirill Tkhai
Reported-by:
Cc: Andrey Ryabinin
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Tetsuo Handa
Cc: Shakeel Butt
Cc:
Cc: Huang Ying
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Aug, 2018
9 commits
-
The patch introduces a special value SHRINKER_REGISTERING to use instead
of list_empty() to differ a registering shrinker from unregistered
shrinker. Why we need that at all?Shrinker registration is split in two parts. The first one is
prealloc_shrinker(), which allocates shrinker memory and reserves ID in
shrinker_idr. This function can fail. The second is
register_shrinker_prepared(), and it finalizes the registration. This
function actually makes shrinker available to be used from
shrink_slab(), and it can't fail.One shrinker may be based on more then one LRU lists. So, we never
clear the bit in memcg shrinker maps, when (one of) corresponding LRU
list becomes empty, since other LRU lists may be not empty. See
superblock shrinker for example: it is based on two LRU lists:
s_inode_lru and s_dentry_lru. We do not want to clear shrinker bit,
when there are no inodes in s_inode_lru, as s_dentry_lru may contain
dentries.Instead of that, we use special algorithm to detect shrinkers having no
elements at all its LRU lists, and this is made in shrink_slab_memcg().
See the comment in this function for the details.Also, in shrink_slab_memcg() we clear shrinker bit in the map, when we
meet unregistered shrinker (bit is set, while there is no a shrinker in
IDR). Otherwise, we would have done that at the moment of shrinker
unregistration for all memcgs (and this looks worse, since iteration
over all memcg may take much time). Also this would have imposed
restrictions on shrinker unregistration order for its users: they would
have had to guarantee, there are no new elements after
unregister_shrinker() (otherwise, a new added element would have set a
bit).So, if we meet a set bit in map and no shrinker in IDR when we're
iterating over the map in shrink_slab_memcg(), this means the
corresponding shrinker is unregistered, and we must clear the bit.Another case is shrinker registration. We want two things there:
1) do_shrink_slab() can be called only for completely registered
shrinkers;2) shrinker internal lists may be populated in any order with
register_shrinker_prepared() (let's talk on the example with sb). Both
of:a)list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru); [cpu0]
memcg_set_shrinker_bit(); [cpu0]
...
register_shrinker_prepared(); [cpu1]and
b)register_shrinker_prepared(); [cpu0]
...
list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru); [cpu1]
memcg_set_shrinker_bit(); [cpu1]are legitimate. We don't want to impose restriction here and to
force people to use only (b) variant. We don't want to force people to
care, there is no elements in LRU lists before the shrinker is
completely registered. Internal users of LRU lists and shrinker code
are two different subsystems, and they have to be closed in themselves
each other.In (a) case we have the bit set before shrinker is completely
registered. We don't want do_shrink_slab() is called at this moment, so
we have to detect such the registering shrinkers.Before this patch list_empty() (shrinker is not linked to the list)
check was used for that. So, in (a) there could be a bit set, but we
don't call do_shrink_slab() unless shrinker is linked to the list. It's
just an indicator, I just overloaded linking to the list.This was not the best solution, since it's better not to touch the
shrinker memory from shrink_slab_memcg() before it's completely
registered (this also will be useful in the future to make shrink_slab()
completely lockless).So, this patch introduces better way to detect registering shrinker,
which allows not to dereference shrinker memory. It's just a ~0UL
value, which we insert into the IDR during ID allocation. After
shrinker is ready to be used, we insert actual shrinker pointer in the
IDR, and it becomes available to shrink_slab_memcg().We can't use NULL instead of this new value for this purpose as:
shrink_slab_memcg() already uses NULL to detect unregistered shrinkers,
and we don't want the function sees NULL and clears the bit, otherwise
(a) won't work.This is the only thing the patch makes: the better way to detect
registering shrinker. Nothing else this patch makes.Also this gives a better assembler, but it's minor side of the patch:
Before:
callq
mov %rax,%r15
test %rax,%rax
je
mov 0x20(%rax),%rax
lea 0x20(%r15),%rdx
cmp %rax,%rdx
je
mov 0x8(%rsp),%edx
mov %r15,%rsi
lea 0x10(%rsp),%rdi
callqAfter:
callq
mov %rax,%r15
lea -0x1(%rax),%rax
cmp $0xfffffffffffffffd,%rax
ja
mov 0x8(%rsp),%edx
mov %r15,%rsi
lea 0x10(%rsp),%rdi
callq ffffffff810cefd0[ktkhai@virtuozzo.com: add #ifdef CONFIG_MEMCG_KMEM around idr_replace()]
Link: http://lkml.kernel.org/r/758b8fec-7573-47eb-b26a-7b2847ae7b8c@virtuozzo.com
Link: http://lkml.kernel.org/r/153355467546.11522.4518015068123480218.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Reviewed-by: Andrew Morton
Cc: Vladimir Davydov
Cc: Michal Hocko
Cc: Andrey Ryabinin
Cc: "Huang, Ying"
Cc: Tetsuo Handa
Cc: Matthew Wilcox
Cc: Shakeel Butt
Cc: Josef Bacik
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In case of shrink_slab_memcg() we do not zero nid, when shrinker is not
numa-aware. This is not a real problem, since currently all memcg-aware
shrinkers are numa-aware too (we have two: super_block shrinker and
workingset shrinker), but something may change in the future.Link: http://lkml.kernel.org/r/153320759911.18959.8842396230157677671.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Reviewed-by: Andrew Morton
Cc: Vladimir Davydov
Cc: Michal Hocko
Cc: Andrey Ryabinin
Cc: "Huang, Ying"
Cc: Tetsuo Handa
Cc: Matthew Wilcox
Cc: Shakeel Butt
Cc: Josef Bacik
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
To avoid further unneed calls of do_shrink_slab() for shrinkers, which
already do not have any charged objects in a memcg, their bits have to
be cleared.This patch introduces a lockless mechanism to do that without races
without parallel list lru add. After do_shrink_slab() returns
SHRINK_EMPTY the first time, we clear the bit and call it once again.
Then we restore the bit, if the new return value is different.Note, that single smp_mb__after_atomic() in shrink_slab_memcg() covers
two situations:1)list_lru_add() shrink_slab_memcg
list_add_tail() for_each_set_bit()
set_bit() do_shrink_slab() before the first call of do_shrink_slab()
instead of this to do not slow down generic case. Also, it's need the
second call as seen in below in (2).2)list_lru_add() shrink_slab_memcg()
list_add_tail() ...
set_bit() ...
... for_each_set_bit()
do_shrink_slab() do_shrink_slab()
clear_bit() ...
... ...
list_lru_add() ...
list_add_tail() clear_bit()
set_bit() do_shrink_slab()The barriers guarantee that the second do_shrink_slab() in the right
side task sees list update if really cleared the bit. This case is
drawn in the code comment.[Results/performance of the patchset]
After the whole patchset applied the below test shows signify increase
of performance:$echo 1 > /sys/fs/cgroup/memory/memory.use_hierarchy
$mkdir /sys/fs/cgroup/memory/ct
$echo 4000M > /sys/fs/cgroup/memory/ct/memory.kmem.limit_in_bytes
$for i in `seq 0 4000`; do mkdir /sys/fs/cgroup/memory/ct/$i;
echo $$ > /sys/fs/cgroup/memory/ct/$i/cgroup.procs;
mkdir -p s/$i; mount -t tmpfs $i s/$i;
touch s/$i/file; doneThen, 5 sequential calls of drop caches:
$time echo 3 > /proc/sys/vm/drop_caches
1)Before:
0.00user 13.78system 0:13.78elapsed 99%CPU
0.00user 5.59system 0:05.60elapsed 99%CPU
0.00user 5.48system 0:05.48elapsed 99%CPU
0.00user 8.35system 0:08.35elapsed 99%CPU
0.00user 8.34system 0:08.35elapsed 99%CPU2)After
0.00user 1.10system 0:01.10elapsed 99%CPU
0.00user 0.00system 0:00.01elapsed 64%CPU
0.00user 0.01system 0:00.01elapsed 82%CPU
0.00user 0.00system 0:00.01elapsed 64%CPU
0.00user 0.01system 0:00.01elapsed 82%CPUThe results show the performance increases at least in 548 times.
Shakeel Butt tested this patchset with fork-bomb on his configuration:
> I created 255 memcgs, 255 ext4 mounts and made each memcg create a
> file containing few KiBs on corresponding mount. Then in a separate
> memcg of 200 MiB limit ran a fork-bomb.
>
> I ran the "perf record -ag -- sleep 60" and below are the results:
>
> Without the patch series:
> Samples: 4M of event 'cycles', Event count (approx.): 3279403076005
> + 36.40% fb.sh [kernel.kallsyms] [k] shrink_slab
> + 18.97% fb.sh [kernel.kallsyms] [k] list_lru_count_one
> + 6.75% fb.sh [kernel.kallsyms] [k] super_cache_count
> + 0.49% fb.sh [kernel.kallsyms] [k] down_read_trylock
> + 0.44% fb.sh [kernel.kallsyms] [k] mem_cgroup_iter
> + 0.27% fb.sh [kernel.kallsyms] [k] up_read
> + 0.21% fb.sh [kernel.kallsyms] [k] osq_lock
> + 0.13% fb.sh [kernel.kallsyms] [k] shmem_unused_huge_count
> + 0.08% fb.sh [kernel.kallsyms] [k] shrink_node_memcg
> + 0.08% fb.sh [kernel.kallsyms] [k] shrink_node
>
> With the patch series:
> Samples: 4M of event 'cycles', Event count (approx.): 2756866824946
> + 47.49% fb.sh [kernel.kallsyms] [k] down_read_trylock
> + 30.72% fb.sh [kernel.kallsyms] [k] up_read
> + 9.51% fb.sh [kernel.kallsyms] [k] mem_cgroup_iter
> + 1.69% fb.sh [kernel.kallsyms] [k] shrink_node_memcg
> + 1.35% fb.sh [kernel.kallsyms] [k] mem_cgroup_protected
> + 1.05% fb.sh [kernel.kallsyms] [k] queued_spin_lock_slowpath
> + 0.85% fb.sh [kernel.kallsyms] [k] _raw_spin_lock
> + 0.78% fb.sh [kernel.kallsyms] [k] lruvec_lru_size
> + 0.57% fb.sh [kernel.kallsyms] [k] shrink_node
> + 0.54% fb.sh [kernel.kallsyms] [k] queue_work_on
> + 0.46% fb.sh [kernel.kallsyms] [k] shrink_slab_memcg[ktkhai@virtuozzo.com: v9]
Link: http://lkml.kernel.org/r/153112561772.4097.11011071937553113003.stgit@localhost.localdomain
Link: http://lkml.kernel.org/r/153063070859.1818.11870882950920963480.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Acked-by: Vladimir Davydov
Tested-by: Shakeel Butt
Cc: Al Viro
Cc: Andrey Ryabinin
Cc: Chris Wilson
Cc: Greg Kroah-Hartman
Cc: Guenter Roeck
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Li RongQing
Cc: Matthew Wilcox
Cc: Matthias Kaehlcke
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Minchan Kim
Cc: Philippe Ombredanne
Cc: Roman Gushchin
Cc: Sahitya Tummala
Cc: Stephen Rothwell
Cc: Tetsuo Handa
Cc: Thomas Gleixner
Cc: Waiman Long
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We need to distinguish the situations when shrinker has very small
amount of objects (see vfs_pressure_ratio() called from
super_cache_count()), and when it has no objects at all. Currently, in
the both of these cases, shrinker::count_objects() returns 0.The patch introduces new SHRINK_EMPTY return value, which will be used
for "no objects at all" case. It's is a refactoring mostly, as
SHRINK_EMPTY is replaced by 0 by all callers of do_shrink_slab() in this
patch, and all the magic will happen in further.Link: http://lkml.kernel.org/r/153063069574.1818.11037751256699341813.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Acked-by: Vladimir Davydov
Tested-by: Shakeel Butt
Cc: Al Viro
Cc: Andrey Ryabinin
Cc: Chris Wilson
Cc: Greg Kroah-Hartman
Cc: Guenter Roeck
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Li RongQing
Cc: Matthew Wilcox
Cc: Matthias Kaehlcke
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Minchan Kim
Cc: Philippe Ombredanne
Cc: Roman Gushchin
Cc: Sahitya Tummala
Cc: Stephen Rothwell
Cc: Tetsuo Handa
Cc: Thomas Gleixner
Cc: Waiman Long
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The patch makes shrink_slab() be called for root_mem_cgroup in the same
way as it's called for the rest of cgroups. This simplifies the logic
and improves the readability.[ktkhai@virtuozzo.com: wrote changelog]
Link: http://lkml.kernel.org/r/153063068338.1818.11496084754797453962.stgit@localhost.localdomain
Signed-off-by: Vladimir Davydov
Signed-off-by: Kirill Tkhai
Tested-by: Shakeel Butt
Cc: Al Viro
Cc: Andrey Ryabinin
Cc: Chris Wilson
Cc: Greg Kroah-Hartman
Cc: Guenter Roeck
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Li RongQing
Cc: Matthew Wilcox
Cc: Matthias Kaehlcke
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Minchan Kim
Cc: Philippe Ombredanne
Cc: Roman Gushchin
Cc: Sahitya Tummala
Cc: Stephen Rothwell
Cc: Tetsuo Handa
Cc: Thomas Gleixner
Cc: Waiman Long
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Using the preparations made in previous patches, in case of memcg
shrink, we may avoid shrinkers, which are not set in memcg's shrinkers
bitmap. To do that, we separate iterations over memcg-aware and
!memcg-aware shrinkers, and memcg-aware shrinkers are chosen via
for_each_set_bit() from the bitmap. In case of big nodes, having many
isolated environments, this gives significant performance growth. See
next patches for the details.Note that the patch does not respect to empty memcg shrinkers, since we
never clear the bitmap bits after we set it once. Their shrinkers will
be called again, with no shrinked objects as result. This functionality
is provided by next patches.[ktkhai@virtuozzo.com: v9]
Link: http://lkml.kernel.org/r/153112558507.4097.12713813335683345488.stgit@localhost.localdomain
Link: http://lkml.kernel.org/r/153063066653.1818.976035462801487910.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Acked-by: Vladimir Davydov
Tested-by: Shakeel Butt
Cc: Al Viro
Cc: Andrey Ryabinin
Cc: Chris Wilson
Cc: Greg Kroah-Hartman
Cc: Guenter Roeck
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Li RongQing
Cc: Matthew Wilcox
Cc: Matthias Kaehlcke
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Minchan Kim
Cc: Philippe Ombredanne
Cc: Roman Gushchin
Cc: Sahitya Tummala
Cc: Stephen Rothwell
Cc: Tetsuo Handa
Cc: Thomas Gleixner
Cc: Waiman Long
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Imagine a big node with many cpus, memory cgroups and containers. Let
we have 200 containers, every container has 10 mounts, and 10 cgroups.
All container tasks don't touch foreign containers mounts. If there is
intensive pages write, and global reclaim happens, a writing task has to
iterate over all memcgs to shrink slab, before it's able to go to
shrink_page_list().Iteration over all the memcg slabs is very expensive: the task has to
visit 200 * 10 = 2000 shrinkers for every memcg, and since there are
2000 memcgs, the total calls are 2000 * 2000 = 4000000.So, the shrinker makes 4 million do_shrink_slab() calls just to try to
isolate SWAP_CLUSTER_MAX pages in one of the actively writing memcg via
shrink_page_list(). I've observed a node spending almost 100% in
kernel, making useless iteration over already shrinked slab.This patch adds bitmap of memcg-aware shrinkers to memcg. The size of
the bitmap depends on bitmap_nr_ids, and during memcg life it's
maintained to be enough to fit bitmap_nr_ids shrinkers. Every bit in
the map is related to corresponding shrinker id.Next patches will maintain set bit only for really charged memcg. This
will allow shrink_slab() to increase its performance in significant way.
See the last patch for the numbers.[ktkhai@virtuozzo.com: v9]
Link: http://lkml.kernel.org/r/153112549031.4097.3576147070498769979.stgit@localhost.localdomain
[ktkhai@virtuozzo.com: add comment to mem_cgroup_css_online()]
Link: http://lkml.kernel.org/r/521f9e5f-c436-b388-fe83-4dc870bfb489@virtuozzo.com
Link: http://lkml.kernel.org/r/153063056619.1818.12550500883688681076.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Acked-by: Vladimir Davydov
Tested-by: Shakeel Butt
Cc: Al Viro
Cc: Andrey Ryabinin
Cc: Chris Wilson
Cc: Greg Kroah-Hartman
Cc: Guenter Roeck
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Li RongQing
Cc: Matthew Wilcox
Cc: Matthias Kaehlcke
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Minchan Kim
Cc: Philippe Ombredanne
Cc: Roman Gushchin
Cc: Sahitya Tummala
Cc: Stephen Rothwell
Cc: Tetsuo Handa
Cc: Thomas Gleixner
Cc: Waiman Long
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Introduce shrinker::id number, which is used to enumerate memcg-aware
shrinkers. The number start from 0, and the code tries to maintain it
as small as possible.This will be used to represent a memcg-aware shrinkers in memcg
shrinkers map.Since all memcg-aware shrinkers are based on list_lru, which is
per-memcg in case of !CONFIG_MEMCG_KMEM only, the new functionality will
be under this config option.[ktkhai@virtuozzo.com: v9]
Link: http://lkml.kernel.org/r/153112546435.4097.10607140323811756557.stgit@localhost.localdomain
Link: http://lkml.kernel.org/r/153063054586.1818.6041047871606697364.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai
Acked-by: Vladimir Davydov
Tested-by: Shakeel Butt
Cc: Al Viro
Cc: Andrey Ryabinin
Cc: Chris Wilson
Cc: Greg Kroah-Hartman
Cc: Guenter Roeck
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Josef Bacik
Cc: Li RongQing
Cc: Matthew Wilcox
Cc: Matthias Kaehlcke
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Minchan Kim
Cc: Philippe Ombredanne
Cc: Roman Gushchin
Cc: Sahitya Tummala
Cc: Stephen Rothwell
Cc: Tetsuo Handa
Cc: Thomas Gleixner
Cc: Waiman Long
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Use smaller scan_control fields for order, priority, and reclaim_idx.
Convert fields from int => s8. All easily fit within a byte:- allocation order range: 0..MAX_ORDER(64?)
- priority range: 0..12(DEF_PRIORITY)
- reclaim_idx range: 0..6(__MAX_NR_ZONES)Since 6538b8ea886e ("x86_64: expand kernel stack to 16K") x86_64 stack
overflows are not an issue. But it's inefficient to use ints.Use s8 (signed byte) rather than u8 to allow for loops like:
do {
...
} while (--sc.priority >= 0);Add BUILD_BUG_ON to verify that s8 is capable of storing max values.
This reduces sizeof(struct scan_control):
- 96 => 80 bytes (x86_64)
- 68 => 56 bytes (i386)scan_control structure field order is changed to utilize padding. After
this patch there is 1 bit of scan_control padding.akpm: makes my vmscan.o's .text 572 bytes smaller as well.
Link: http://lkml.kernel.org/r/20180530061212.84915-1-gthelen@google.com
Signed-off-by: Greg Thelen
Suggested-by: Matthew Wilcox
Reviewed-by: Andrew Morton
Cc: Michal Hocko
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 Jun, 2018
2 commits
-
Memory controller implements the memory.low best-effort memory
protection mechanism, which works perfectly in many cases and allows
protecting working sets of important workloads from sudden reclaim.But its semantics has a significant limitation: it works only as long as
there is a supply of reclaimable memory. This makes it pretty useless
against any sort of slow memory leaks or memory usage increases. This
is especially true for swapless systems. If swap is enabled, memory
soft protection effectively postpones problems, allowing a leaking
application to fill all swap area, which makes no sense. The only
effective way to guarantee the memory protection in this case is to
invoke the OOM killer.It's possible to handle this case in userspace by reacting on MEMCG_LOW
events; but there is still a place for a fail-safe in-kernel mechanism
to provide stronger guarantees.This patch introduces the memory.min interface for cgroup v2 memory
controller. It works very similarly to memory.low (sharing the same
hierarchical behavior), except that it's not disabled if there is no
more reclaimable memory in the system.If cgroup is not populated, its memory.min is ignored, because otherwise
even the OOM killer wouldn't be able to reclaim the protected memory,
and the system can stall.[guro@fb.com: s/low/min/ in docs]
Link: http://lkml.kernel.org/r/20180510130758.GA9129@castle.DHCP.thefacebook.com
Link: http://lkml.kernel.org/r/20180509180734.GA4856@castle.DHCP.thefacebook.com
Signed-off-by: Roman Gushchin
Reviewed-by: Randy Dunlap
Acked-by: Johannes Weiner
Cc: Michal Hocko
Cc: Vladimir Davydov
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
While revisiting my Btrfs swapfile series [1], I introduced a situation
in which reclaim would lock i_rwsem, and even though the swapon() path
clearly made GFP_KERNEL allocations while holding i_rwsem, I got no
complaints from lockdep. It turns out that the rework of the fs_reclaim
annotation was broken: if the current task has PF_MEMALLOC set, we don't
acquire the dummy fs_reclaim lock, but when reclaiming we always check
this _after_ we've just set the PF_MEMALLOC flag. In most cases, we can
fix this by moving the fs_reclaim_{acquire,release}() outside of the
memalloc_noreclaim_{save,restore}(), althought kswapd is slightly
different. After applying this, I got the expected lockdep splats.1: https://lwn.net/Articles/625412/
Link: http://lkml.kernel.org/r/9f8aa70652a98e98d7c4de0fc96a4addcee13efe.1523778026.git.osandov@fb.com
Fixes: d92a8cfcb37e ("locking/lockdep: Rework FS_RECLAIM annotation")
Signed-off-by: Omar Sandoval
Reviewed-by: Andrew Morton
Cc: Peter Zijlstra
Cc: Tetsuo Handa
Cc: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
03 Jun, 2018
1 commit
-
George Boole would have noticed a slight error in 4.16 commit
69d763fc6d3a ("mm: pin address_space before dereferencing it while
isolating an LRU page"). Fix it, to match both the comment above it,
and the original behaviour.Although anonymous pages are not marked PageDirty at first, we have an
old habit of calling SetPageDirty when a page is removed from swap
cache: so there's a category of ex-swap pages that are easily
migratable, but were inadvertently excluded from compaction's async
migration in 4.16.Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1805302014001.12558@eggly.anvils
Fixes: 69d763fc6d3a ("mm: pin address_space before dereferencing it while isolating an LRU page")
Signed-off-by: Hugh Dickins
Acked-by: Minchan Kim
Acked-by: Mel Gorman
Reported-by: Ivan Kalvachev
Cc: "Huang, Ying"
Cc: Jan Kara
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Apr, 2018
1 commit
-
syzbot is catching so many bugs triggered by commit 9ee332d99e4d5a97
("sget(): handle failures of register_shrinker()"). That commit expected
that calling kill_sb() from deactivate_locked_super() without successful
fill_super() is safe, but the reality was different; some callers assign
attributes which are needed for kill_sb() after sget() succeeds.For example, [1] is a report where sb->s_mode (which seems to be either
FMODE_READ | FMODE_EXCL | FMODE_WRITE or FMODE_READ | FMODE_EXCL) is not
assigned unless sget() succeeds. But it does not worth complicate sget()
so that register_shrinker() failure path can safely call
kill_block_super() via kill_sb(). Making alloc_super() fail if memory
allocation for register_shrinker() failed is much simpler. Let's avoid
calling deactivate_locked_super() from sget_userns() by preallocating
memory for the shrinker and making register_shrinker() in sget_userns()
never fail.[1] https://syzkaller.appspot.com/bug?id=588996a25a2587be2e3a54e8646728fb9cae44e7
Signed-off-by: Tetsuo Handa
Reported-by: syzbot
Cc: Al Viro
Cc: Michal Hocko
Signed-off-by: Al Viro
12 Apr, 2018
7 commits
-
Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root. Rename the address_space ->page_tree to ->i_pages,
since we don't really care that it's a tree.[willy@infradead.org: fix nds32, fs/dax.c]
Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org
Signed-off-by: Matthew Wilcox
Acked-by: Jeff Layton
Cc: Darrick J. Wong
Cc: Dave Chinner
Cc: Ryusuke Konishi
Cc: Will Deacon
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Commit a983b5ebee57 ("mm: memcontrol: fix excessive complexity in
memory.stat reporting") added per-cpu drift to all memory cgroup stats
and events shown in memory.stat and memory.events.For memory.stat this is acceptable. But memory.events issues file
notifications, and somebody polling the file for changes will be
confused when the counters in it are unchanged after a wakeup.Luckily, the events in memory.events - MEMCG_LOW, MEMCG_HIGH, MEMCG_MAX,
MEMCG_OOM - are sufficiently rare and high-level that we don't need
per-cpu buffering for them: MEMCG_HIGH and MEMCG_MAX would be the most
frequent, but they're counting invocations of reclaim, which is a
complex operation that touches many shared cachelines.This splits memory.events from the generic VM events and tracks them in
their own, unbuffered atomic counters. That's also cleaner, as it
eliminates the ugly enum nesting of VM and cgroup events.[hannes@cmpxchg.org: "array subscript is above array bounds"]
Link: http://lkml.kernel.org/r/20180406155441.GA20806@cmpxchg.org
Link: http://lkml.kernel.org/r/20180405175507.GA24817@cmpxchg.org
Fixes: a983b5ebee57 ("mm: memcontrol: fix excessive complexity in memory.stat reporting")
Signed-off-by: Johannes Weiner
Reported-by: Tejun Heo
Acked-by: Tejun Heo
Acked-by: Michal Hocko
Cc: Vladimir Davydov
Cc: Roman Gushchin
Cc: Rik van Riel
Cc: Stephen Rothwell
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The trace event trace_mm_vmscan_lru_shrink_inactive() currently has 12
parameters! Seven of them are from the reclaim_stat structure. This
structure is currently local to mm/vmscan.c. By moving it to the global
vmstat.h header, we can also reference it from the vmscan tracepoints.
In moving it, it brings down the overhead of passing so many arguments
to the trace event. In the future, we may limit the number of arguments
that a trace event may pass (ideally just 6, but more realistically it
may be 8).Before this patch, the code to call the trace event is this:
0f 83 aa fe ff ff jae ffffffff811e6261
48 8b 45 a0 mov -0x60(%rbp),%rax
45 8b 64 24 20 mov 0x20(%r12),%r12d
44 8b 6d d4 mov -0x2c(%rbp),%r13d
8b 4d d0 mov -0x30(%rbp),%ecx
44 8b 75 cc mov -0x34(%rbp),%r14d
44 8b 7d c8 mov -0x38(%rbp),%r15d
48 89 45 90 mov %rax,-0x70(%rbp)
8b 83 b8 fe ff ff mov -0x148(%rbx),%eax
8b 55 c0 mov -0x40(%rbp),%edx
8b 7d c4 mov -0x3c(%rbp),%edi
8b 75 b8 mov -0x48(%rbp),%esi
89 45 80 mov %eax,-0x80(%rbp)
65 ff 05 e4 f7 e2 7e incl %gs:0x7ee2f7e4(%rip) # 15bd0
48 8b 05 75 5b 13 01 mov 0x1135b75(%rip),%rax # ffffffff8231bf68
48 85 c0 test %rax,%rax
74 72 je ffffffff811e646a
48 89 c3 mov %rax,%rbx
4c 8b 10 mov (%rax),%r10
89 f8 mov %edi,%eax
48 89 85 68 ff ff ff mov %rax,-0x98(%rbp)
89 f0 mov %esi,%eax
48 89 85 60 ff ff ff mov %rax,-0xa0(%rbp)
89 c8 mov %ecx,%eax
48 89 85 78 ff ff ff mov %rax,-0x88(%rbp)
89 d0 mov %edx,%eax
48 89 85 70 ff ff ff mov %rax,-0x90(%rbp)
8b 45 8c mov -0x74(%rbp),%eax
48 8b 7b 08 mov 0x8(%rbx),%rdi
48 83 c3 18 add $0x18,%rbx
50 push %rax
41 54 push %r12
41 55 push %r13
ff b5 78 ff ff ff pushq -0x88(%rbp)
41 56 push %r14
41 57 push %r15
ff b5 70 ff ff ff pushq -0x90(%rbp)
4c 8b 8d 68 ff ff ff mov -0x98(%rbp),%r9
4c 8b 85 60 ff ff ff mov -0xa0(%rbp),%r8
48 8b 4d 98 mov -0x68(%rbp),%rcx
48 8b 55 90 mov -0x70(%rbp),%rdx
8b 75 80 mov -0x80(%rbp),%esi
41 ff d2 callq *%r10After the patch:
0f 83 a8 fe ff ff jae ffffffff811e626d
8b 9b b8 fe ff ff mov -0x148(%rbx),%ebx
45 8b 64 24 20 mov 0x20(%r12),%r12d
4c 8b 6d a0 mov -0x60(%rbp),%r13
65 ff 05 f5 f7 e2 7e incl %gs:0x7ee2f7f5(%rip) # 15bd0
4c 8b 35 86 5b 13 01 mov 0x1135b86(%rip),%r14 # ffffffff8231bf68
4d 85 f6 test %r14,%r14
74 2a je ffffffff811e6411
49 8b 06 mov (%r14),%rax
8b 4d 8c mov -0x74(%rbp),%ecx
49 8b 7e 08 mov 0x8(%r14),%rdi
49 83 c6 18 add $0x18,%r14
4c 89 ea mov %r13,%rdx
45 89 e1 mov %r12d,%r9d
4c 8d 45 b8 lea -0x48(%rbp),%r8
89 de mov %ebx,%esi
51 push %rcx
48 8b 4d 98 mov -0x68(%rbp),%rcx
ff d0 callq *%raxLink: http://lkml.kernel.org/r/2559d7cb-ec60-1200-2362-04fa34fd02bb@fb.com
Link: http://lkml.kernel.org/r/20180322121003.4177af15@gandalf.local.home
Signed-off-by: Steven Rostedt (VMware)
Reported-by: Alexei Starovoitov
Acked-by: David Rientjes
Acked-by: Michal Hocko
Cc: Mel Gorman
Cc: Vlastimil Babka
Cc: Andrey Ryabinin
Cc: Alexei Starovoitov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
memcg reclaim may alter pgdat->flags based on the state of LRU lists in
cgroup and its children. PGDAT_WRITEBACK may force kswapd to sleep
congested_wait(), PGDAT_DIRTY may force kswapd to writeback filesystem
pages. But the worst here is PGDAT_CONGESTED, since it may force all
direct reclaims to stall in wait_iff_congested(). Note that only kswapd
have powers to clear any of these bits. This might just never happen if
cgroup limits configured that way. So all direct reclaims will stall as
long as we have some congested bdi in the system.Leave all pgdat->flags manipulations to kswapd. kswapd scans the whole
pgdat, only kswapd can clear pgdat->flags once node is balanced, thus
it's reasonable to leave all decisions about node state to kswapd.Why only kswapd? Why not allow to global direct reclaim change these
flags? It is because currently only kswapd can clear these flags. I'm
less worried about the case when PGDAT_CONGESTED falsely not set, and
more worried about the case when it falsely set. If direct reclaimer
sets PGDAT_CONGESTED, do we have guarantee that after the congestion
problem is sorted out, kswapd will be woken up and clear the flag? It
seems like there is no such guarantee. E.g. direct reclaimers may
eventually balance pgdat and kswapd simply won't wake up (see
wakeup_kswapd()).Moving pgdat->flags manipulation to kswapd, means that cgroup2 recalim
now loses its congestion throttling mechanism. Add per-cgroup
congestion state and throttle cgroup2 reclaimers if memcg is in
congestion state.Currently there is no need in per-cgroup PGDAT_WRITEBACK and PGDAT_DIRTY
bits since they alter only kswapd behavior.The problem could be easily demonstrated by creating heavy congestion in
one cgroup:echo "+memory" > /sys/fs/cgroup/cgroup.subtree_control
mkdir -p /sys/fs/cgroup/congester
echo 512M > /sys/fs/cgroup/congester/memory.max
echo $$ > /sys/fs/cgroup/congester/cgroup.procs
/* generate a lot of diry data on slow HDD */
while true; do dd if=/dev/zero of=/mnt/sdb/zeroes bs=1M count=1024; done &
....
while true; do dd if=/dev/zero of=/mnt/sdb/zeroes bs=1M count=1024; done &and some job in another cgroup:
mkdir /sys/fs/cgroup/victim
echo 128M > /sys/fs/cgroup/victim/memory.max# time cat /dev/sda > /dev/null
real 10m15.054s
user 0m0.487s
sys 1m8.505sAccording to the tracepoint in wait_iff_congested(), the 'cat' spent 50%
of the time sleeping there.With the patch, cat don't waste time anymore:
# time cat /dev/sda > /dev/null
real 5m32.911s
user 0m0.411s
sys 0m56.664s[aryabinin@virtuozzo.com: congestion state should be per-node]
Link: http://lkml.kernel.org/r/20180406135215.10057-1-aryabinin@virtuozzo.com
[ayabinin@virtuozzo.com: make congestion state per-cgroup-per-node instead of just per-cgroup[
Link: http://lkml.kernel.org/r/20180406180254.8970-2-aryabinin@virtuozzo.com
Link: http://lkml.kernel.org/r/20180323152029.11084-5-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin
Reviewed-by: Shakeel Butt
Acked-by: Johannes Weiner
Cc: Mel Gorman
Cc: Tejun Heo
Cc: Michal Hocko
Cc: Steven Rostedt
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We have separate LRU list for each memory cgroup. Memory reclaim
iterates over cgroups and calls shrink_inactive_list() every inactive
LRU list. Based on the state of a single LRU shrink_inactive_list() may
flag the whole node as dirty,congested or under writeback. This is
obviously wrong and hurtful. It's especially hurtful when we have
possibly small congested cgroup in system. Than *all* direct reclaims
waste time by sleeping in wait_iff_congested(). And the more memcgs in
the system we have the longer memory allocation stall is, because
wait_iff_congested() called on each lru-list scan.Sum reclaim stats across all visited LRUs on node and flag node as
dirty, congested or under writeback based on that sum. Also call
congestion_wait(), wait_iff_congested() once per pgdat scan, instead of
once per lru-list scan.This only fixes the problem for global reclaim case. Per-cgroup reclaim
may alter global pgdat flags too, which is wrong. But that is separate
issue and will be addressed in the next patch.This change will not have any effect on a systems with all workload
concentrated in a single cgroup.[aryabinin@virtuozzo.com: check nr_writeback against all nr_taken, not just file]
Link: http://lkml.kernel.org/r/20180406180254.8970-1-aryabinin@virtuozzo.com
Link: http://lkml.kernel.org/r/20180323152029.11084-4-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin
Reviewed-by: Shakeel Butt
Cc: Mel Gorman
Cc: Tejun Heo
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Steven Rostedt
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Only kswapd can have non-zero nr_immediate, and current_may_throttle()
is always true for kswapd (PF_LESS_THROTTLE bit is never set) thus it's
enough to check stat.nr_immediate only.Link: http://lkml.kernel.org/r/20180315164553.17856-4-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin
Acked-by: Michal Hocko
Cc: Shakeel Butt
Cc: Mel Gorman
Cc: Tejun Heo
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Update some comments that became stale since transiton from per-zone to
per-node reclaim.Link: http://lkml.kernel.org/r/20180315164553.17856-2-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin
Acked-by: Michal Hocko
Cc: Shakeel Butt
Cc: Mel Gorman
Cc: Tejun Heo
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
06 Apr, 2018
3 commits
-
Kswapd will not wakeup if per-zone watermarks are not failing or if too
many previous attempts at background reclaim have failed.This can be true if there is a lot of free memory available. For high-
order allocations, kswapd is responsible for waking up kcompactd for
background compaction. If the zone is not below its watermarks or
reclaim has recently failed (lots of free memory, nothing left to
reclaim), kcompactd does not get woken up.When __GFP_DIRECT_RECLAIM is not allowed, allow kcompactd to still be
woken up even if kswapd will not reclaim. This allows high-order
allocations, such as thp, to still trigger background compaction even
when the zone has an abundance of free memory.Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1803111659420.209721@chino.kir.corp.google.com
Signed-off-by: David Rientjes
Acked-by: Vlastimil Babka
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Since we no longer use return value of shrink_slab() for normal reclaim,
the comment is no longer true. If some do_shrink_slab() call takes
unexpectedly long (root cause of stall is currently unknown) when
register_shrinker()/unregister_shrinker() is pending, trying to drop
caches via /proc/sys/vm/drop_caches could become infinite cond_resched()
loop if many mem_cgroup are defined. For safety, let's not pretend
forward progress.Link: http://lkml.kernel.org/r/201802202229.GGF26507.LVFtMSOOHFJOQF@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa
Acked-by: Michal Hocko
Reviewed-by: Andrew Morton
Cc: Dave Chinner
Cc: Glauber Costa
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When page_mapping() is called and the mapping is dereferenced in
page_evicatable() through shrink_active_list(), it is possible for the
inode to be truncated and the embedded address space to be freed at the
same time. This may lead to the following race.CPU1 CPU2
truncate(inode) shrink_active_list()
... page_evictable(page)
truncate_inode_page(mapping, page);
delete_from_page_cache(page)
spin_lock_irqsave(&mapping->tree_lock, flags);
__delete_from_page_cache(page, NULL)
page_cache_tree_delete(..)
... mapping = page_mapping(page);
page->mapping = NULL;
...
spin_unlock_irqrestore(&mapping->tree_lock, flags);
page_cache_free_page(mapping, page)
put_page(page)
if (put_page_testzero(page)) -> false
- inode now has no pages and can be freed including embedded address_spacemapping_unevictable(mapping)
test_bit(AS_UNEVICTABLE, &mapping->flags);
- we've dereferenced mapping which is potentially already free.Similar race exists between swap cache freeing and page_evicatable()
too.The address_space in inode and swap cache will be freed after a RCU
grace period. So the races are fixed via enclosing the page_mapping()
and address_space usage in rcu_read_lock/unlock(). Some comments are
added in code to make it clear what is protected by the RCU read lock.Link: http://lkml.kernel.org/r/20180212081227.1940-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying"
Reviewed-by: Jan Kara
Reviewed-by: Andrew Morton
Cc: Mel Gorman
Cc: Minchan Kim
Cc: "Huang, Ying"
Cc: Johannes Weiner
Cc: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 Mar, 2018
1 commit
-
Commit 726d061fbd36 ("mm: vmscan: kick flushers when we encounter dirty
pages on the LRU") added flusher invocation to shrink_inactive_list()
when many dirty pages on the LRU are encountered.However, shrink_inactive_list() doesn't wake up flushers for legacy
cgroup reclaim, so the next commit bbef938429f5 ("mm: vmscan: remove old
flusher wakeup from direct reclaim path") removed the only source of
flusher's wake up in legacy mem cgroup reclaim path.This leads to premature OOM if there is too many dirty pages in cgroup:
# mkdir /sys/fs/cgroup/memory/test
# echo $$ > /sys/fs/cgroup/memory/test/tasks
# echo 50M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes
# dd if=/dev/zero of=tmp_file bs=1M count=100
Killeddd invoked oom-killer: gfp_mask=0x14000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=0
Call Trace:
dump_stack+0x46/0x65
dump_header+0x6b/0x2ac
oom_kill_process+0x21c/0x4a0
out_of_memory+0x2a5/0x4b0
mem_cgroup_out_of_memory+0x3b/0x60
mem_cgroup_oom_synchronize+0x2ed/0x330
pagefault_out_of_memory+0x24/0x54
__do_page_fault+0x521/0x540
page_fault+0x45/0x50Task in /test killed as a result of limit of /test
memory: usage 51200kB, limit 51200kB, failcnt 73
memory+swap: usage 51200kB, limit 9007199254740988kB, failcnt 0
kmem: usage 296kB, limit 9007199254740988kB, failcnt 0
Memory cgroup stats for /test: cache:49632KB rss:1056KB rss_huge:0KB shmem:0KB
mapped_file:0KB dirty:49500KB writeback:0KB swap:0KB inactive_anon:0KB
active_anon:1168KB inactive_file:24760KB active_file:24960KB unevictable:0KB
Memory cgroup out of memory: Kill process 3861 (bash) score 88 or sacrifice child
Killed process 3876 (dd) total-vm:8484kB, anon-rss:1052kB, file-rss:1720kB, shmem-rss:0kB
oom_reaper: reaped process 3876 (dd), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kBWake up flushers in legacy cgroup reclaim too.
Link: http://lkml.kernel.org/r/20180315164553.17856-1-aryabinin@virtuozzo.com
Fixes: bbef938429f5 ("mm: vmscan: remove old flusher wakeup from direct reclaim path")
Signed-off-by: Andrey Ryabinin
Tested-by: Shakeel Butt
Acked-by: Michal Hocko
Cc: Mel Gorman
Cc: Tejun Heo
Cc: Johannes Weiner
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds