26 Jun, 2015
1 commit
-
Pull cgroup writeback support from Jens Axboe:
"This is the big pull request for adding cgroup writeback support.This code has been in development for a long time, and it has been
simmering in for-next for a good chunk of this cycle too. This is one
of those problems that has been talked about for at least half a
decade, finally there's a solution and code to go with it.Also see last weeks writeup on LWN:
http://lwn.net/Articles/648292/"
* 'for-4.2/writeback' of git://git.kernel.dk/linux-block: (85 commits)
writeback, blkio: add documentation for cgroup writeback support
vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
writeback: do foreign inode detection iff cgroup writeback is enabled
v9fs: fix error handling in v9fs_session_init()
bdi: fix wrong error return value in cgwb_create()
buffer: remove unusued 'ret' variable
writeback: disassociate inodes from dying bdi_writebacks
writeback: implement foreign cgroup inode bdi_writeback switching
writeback: add lockdep annotation to inode_to_wb()
writeback: use unlocked_inode_to_wb transaction in inode_congested()
writeback: implement unlocked_inode_to_wb transaction and use it for stat updates
writeback: implement [locked_]inode_to_wb_and_lock_list()
writeback: implement foreign cgroup inode detection
writeback: make writeback_control track the inode being written back
writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()
mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
writeback: implement memcg writeback domain based throttling
writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes
writeback: implement memcg wb_domain
writeback: update wb_over_bg_thresh() to use wb_domain aware operations
...
25 Jun, 2015
4 commits
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memcg->under_oom tracks whether the memcg is under OOM conditions and is
an atomic_t counter managed with mem_cgroup_[un]mark_under_oom(). While
atomic_t appears to be simple synchronization-wise, when used as a
synchronization construct like here, it's trickier and more error-prone
due to weak memory ordering rules, especially around atomic_read(), and
false sense of security.For example, both non-trivial read sites of memcg->under_oom are a bit
problematic although not being actually broken.* mem_cgroup_oom_register_event()
It isn't explicit what guarantees the memory ordering between event
addition and memcg->under_oom check. This isn't broken only because
memcg_oom_lock is used for both event list and memcg->oom_lock.* memcg_oom_recover()
The lockless test doesn't have any explanation why this would be
safe.mem_cgroup_[un]mark_under_oom() are very cold paths and there's no point
in avoiding locking memcg_oom_lock there. This patch converts
memcg->under_oom from atomic_t to int, puts their modifications under
memcg_oom_lock and documents why the lockless test in
memcg_oom_recover() is safe.Signed-off-by: Tejun Heo
Acked-by: Michal Hocko
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Since commit 4942642080ea ("mm: memcg: handle non-error OOM situations
more gracefully"), nobody uses mem_cgroup->oom_wakeups. Remove it.While at it, also fold memcg_wakeup_oom() into memcg_oom_recover() which
is its only user. This cleanup was suggested by Michal.Signed-off-by: Tejun Heo
Acked-by: Michal Hocko
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The zonelist locking and the oom_sem are two overlapping locks that are
used to serialize global OOM killing against different things.The historical zonelist locking serializes OOM kills from allocations with
overlapping zonelists against each other to prevent killing more tasks
than necessary in the same memory domain. Only when neither tasklists nor
zonelists from two concurrent OOM kills overlap (tasks in separate memcgs
bound to separate nodes) are OOM kills allowed to execute in parallel.The younger oom_sem is a read-write lock to serialize OOM killing against
the PM code trying to disable the OOM killer altogether.However, the OOM killer is a fairly cold error path, there is really no
reason to optimize for highly performant and concurrent OOM kills. And
the oom_sem is just flat-out redundant.Replace both locking schemes with a single global mutex serializing OOM
kills regardless of context.Signed-off-by: Johannes Weiner
Acked-by: Michal Hocko
Acked-by: David Rientjes
Cc: Tetsuo Handa
Cc: Andrea Arcangeli
Cc: Dave Chinner
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Rename unmark_oom_victim() to exit_oom_victim(). Marking and unmarking
are related in functionality, but the interface is not symmetrical at
all: one is an internal OOM killer function used during the killing, the
other is for an OOM victim to signal its own death on exit later on.
This has locking implications, see follow-up changes.While at it, rename mark_tsk_oom_victim() to mark_oom_victim(), which
is easier on the eye.Signed-off-by: Johannes Weiner
Acked-by: David Rientjes
Acked-by: Michal Hocko
Cc: Tetsuo Handa
Cc: Andrea Arcangeli
Cc: Dave Chinner
Cc: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Jun, 2015
2 commits
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On -rt, the VM_BUG_ON(!irqs_disabled()) triggers inside the memcg
swapout path because the spin_lock_irq(&mapping->tree_lock) in the
caller doesn't actually disable the hardware interrupts - which is fine,
because on -rt the tophalves run in process context and so we are still
safe from preemption while updating the statistics.Remove the VM_BUG_ON() but keep the comment of what we rely on.
Signed-off-by: Johannes Weiner
Reported-by: Clark Williams
Cc: Fernando Lopez-Lezcano
Cc: Steven Rostedt
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When trimming memcg consumption excess (see memory.high), we call
try_to_free_mem_cgroup_pages without checking if we are allowed to sleep
in the current context, which can result in a deadlock. Fix this.Fixes: 241994ed8649 ("mm: memcontrol: default hierarchy interface for memory")
Signed-off-by: Vladimir Davydov
Cc: Johannes Weiner
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
02 Jun, 2015
8 commits
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While cgroup writeback support now connects memcg and blkcg so that
writeback IOs are properly attributed and controlled, the IO back
pressure propagation mechanism implemented in balance_dirty_pages()
and its subroutines wasn't aware of cgroup writeback.Processes belonging to a memcg may have access to only subset of total
memory available in the system and not factoring this into dirty
throttling rendered it completely ineffective for processes under
memcg limits and memcg ended up building a separate ad-hoc degenerate
mechanism directly into vmscan code to limit page dirtying.The previous patches updated balance_dirty_pages() and its subroutines
so that they can deal with multiple wb_domain's (writeback domains)
and defined per-memcg wb_domain. Processes belonging to a non-root
memcg are bound to two wb_domains, global wb_domain and memcg
wb_domain, and should be throttled according to IO pressures from both
domains. This patch updates dirty throttling code so that it repeats
similar calculations for the two domains - the differences between the
two are few and minor - and applies the lower of the two sets of
resulting constraints.wb_over_bg_thresh(), which controls when background writeback
terminates, is also updated to consider both global and memcg
wb_domains. It returns true if dirty is over bg_thresh for either
domain.This makes the dirty throttling mechanism operational for memcg
domains including writeback-bandwidth-proportional dirty page
distribution inside them but the ad-hoc memcg throttling mechanism in
vmscan is still in place. The next patch will rip it out.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
The amount of available memory to a memcg wb_domain can change as
memcg configuration changes. A domain's ->dirty_limit exists to
smooth out sudden drops in dirty threshold; however, when a domain's
size actually drops significantly, it hinders the dirty throttling
from adjusting to the new configuration leading to unexpected
behaviors including unnecessary OOM kills.This patch resolves the issue by adding wb_domain_size_changed() which
resets ->dirty_limit[_tstmp] and making memcg call it on configuration
changes.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
Dirtyable memory is distributed to a wb (bdi_writeback) according to
the relative bandwidth the wb is writing out in the whole system.
This distribution is global - each wb is measured against all other
wb's and gets the proportinately sized portion of the memory in the
whole system.For cgroup writeback, the amount of dirtyable memory is scoped by
memcg and thus each wb would need to be measured and controlled in its
memcg. IOW, a wb will belong to two writeback domains - the global
and memcg domains.The previous patches laid the groundwork to support the two wb_domains
and this patch implements memcg wb_domain. memcg->cgwb_domain is
initialized on css online and destroyed on css release,
wb->memcg_completions is added, and __wb_writeout_inc() is updated to
increment completions against both global and memcg wb_domains.The following patches will update balance_dirty_pages() and its
subroutines to actually consider memcg wb_domain for throttling.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
cpu_possible_mask represents the CPUs which are actually possible
during that boot instance. For systems which don't support CPU
hotplug, this will match cpu_online_mask exactly in most cases. Even
for systems which support CPU hotplug, the number of possible CPU
slots is highly unlikely to diverge greatly from the number of online
CPUs. The only cases where the difference between possible and online
caused problems were when the boot code failed to initialize the
possible mask and left it fully set at NR_CPUS - 1.As such, most per-cpu constructs allocate for all possible CPUs and
often iterate over the possibles, which also has the benefit of
avoiding the blocking CPU hotplug synchronization.memcg open codes per-cpu stat counting for mem_cgroup_read_stat() and
mem_cgroup_read_events(), which iterates over online CPUs and handles
CPU hotplug operations explicitly. This complexity doesn't actually
buy anything. Switch to iterating over the possibles and drop the
explicit CPU hotplug handling.Eventually, we want to convert memcg to use percpu_counter instead of
its own custom implementation which also benefits from quick access
w/o summing for cases where larger error margin is acceptable.This will allow mem_cgroup_read_stat() to be called from non-sleepable
contexts which will be used by cgroup writeback.Signed-off-by: Tejun Heo
Cc: Michal Hocko
Acked-by: Johannes Weiner
Signed-off-by: Jens Axboe -
For the planned cgroup writeback support, on each bdi
(backing_dev_info), each memcg will be served by a separate wb
(bdi_writeback). This patch updates bdi so that a bdi can host
multiple wbs (bdi_writebacks).On the default hierarchy, blkcg implicitly enables memcg. This allows
using memcg's page ownership for attributing writeback IOs, and every
memcg - blkcg combination can be served by its own wb by assigning a
dedicated wb to each memcg. This means that there may be multiple
wb's of a bdi mapped to the same blkcg. As congested state is per
blkcg - bdi combination, those wb's should share the same congested
state. This is achieved by tracking congested state via
bdi_writeback_congested structs which are keyed by blkcg.bdi->wb remains unchanged and will keep serving the root cgroup.
cgwb's (cgroup wb's) for non-root cgroups are created on-demand or
looked up while dirtying an inode according to the memcg of the page
being dirtied or current task. Each cgwb is indexed on bdi->cgwb_tree
by its memcg id. Once an inode is associated with its wb, it can be
retrieved using inode_to_wb().Currently, none of the filesystems has FS_CGROUP_WRITEBACK and all
pages will keep being associated with bdi->wb.v3: inode_attach_wb() in account_page_dirtied() moved inside
mapping_cap_account_dirty() block where it's known to be !NULL.
Also, an unnecessary NULL check before kfree() removed. Both
detected by the kbuild bot.v2: Updated so that wb association is per inode and wb is per memcg
rather than blkcg.Signed-off-by: Tejun Heo
Cc: kbuild test robot
Cc: Dan Carpenter
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
Implement mem_cgroup_css_from_page() which returns the
cgroup_subsys_state of the memcg associated with a given page on the
default hierarchy. This will be used by cgroup writeback support.This function assumes that page->mem_cgroup association doesn't change
until the page is released, which is true on the default hierarchy as
long as replace_page_cache_page() is not used. As the only user of
replace_page_cache_page() is FUSE which won't support cgroup writeback
for the time being, this works for now, and replace_page_cache_page()
will soon be updated so that the invariant actually holds.Note that the RCU protected page->mem_cgroup access is consistent with
other usages across memcg but ultimately incorrect. These unlocked
accesses are missing required barriers. page->mem_cgroup should be
made an RCU pointer and updated and accessed using RCU operations.v4: Instead of triggering WARN, return the root css on the traditional
hierarchies. This makes the function a lot easier to deal with
especially as there's no light way to synchronize against
hierarchy rebinding.v3: s/mem_cgroup_migrate()/mem_cgroup_css_from_page()/
v2: Trigger WARN if the function is used on the traditional
hierarchies and add comment about the assumed invariant.Signed-off-by: Tejun Heo
Cc: Johannes Weiner
Cc: Michal Hocko
Signed-off-by: Jens Axboe -
Add global mem_cgroup_root_css which points to the root memcg css.
This will be used by cgroup writeback support. If memcg is disabled,
it's defined as ERR_PTR(-EINVAL).Signed-off-by: Tejun Heo
Cc: Johannes Weiner
aCc: Michal Hocko
Signed-off-by: Jens Axboe -
When modifying PG_Dirty on cached file pages, update the new
MEM_CGROUP_STAT_DIRTY counter. This is done in the same places where
global NR_FILE_DIRTY is managed. The new memcg stat is visible in the
per memcg memory.stat cgroupfs file. The most recent past attempt at
this was http://thread.gmane.org/gmane.linux.kernel.cgroups/8632The new accounting supports future efforts to add per cgroup dirty
page throttling and writeback. It also helps an administrator break
down a container's memory usage and provides evidence to understand
memcg oom kills (the new dirty count is included in memcg oom kill
messages).The ability to move page accounting between memcg
(memory.move_charge_at_immigrate) makes this accounting more
complicated than the global counter. The existing
mem_cgroup_{begin,end}_page_stat() lock is used to serialize move
accounting with stat updates.
Typical update operation:
memcg = mem_cgroup_begin_page_stat(page)
if (TestSetPageDirty()) {
[...]
mem_cgroup_update_page_stat(memcg)
}
mem_cgroup_end_page_stat(memcg)Summary of mem_cgroup_end_page_stat() overhead:
- Without CONFIG_MEMCG it's a no-op
- With CONFIG_MEMCG and no inter memcg task movement, it's just
rcu_read_lock()
- With CONFIG_MEMCG and inter memcg task movement, it's
rcu_read_lock() + spin_lock_irqsave()A memcg parameter is added to several routines because their callers
now grab mem_cgroup_begin_page_stat() which returns the memcg later
needed by for mem_cgroup_update_page_stat().Because mem_cgroup_begin_page_stat() may disable interrupts, some
adjustments are needed:
- move __mark_inode_dirty() from __set_page_dirty() to its caller.
__mark_inode_dirty() locking does not want interrupts disabled.
- use spin_lock_irqsave(tree_lock) rather than spin_lock_irq() in
__delete_from_page_cache(), replace_page_cache_page(),
invalidate_complete_page2(), and __remove_mapping().text data bss dec hex filename
8925147 1774832 1785856 12485835 be84cb vmlinux-!CONFIG_MEMCG-before
8925339 1774832 1785856 12486027 be858b vmlinux-!CONFIG_MEMCG-after
+192 text bytes
8965977 1784992 1785856 12536825 bf4bf9 vmlinux-CONFIG_MEMCG-before
8966750 1784992 1785856 12537598 bf4efe vmlinux-CONFIG_MEMCG-after
+773 text bytesPerformance tests run on v4.0-rc1-36-g4f671fe2f952. Lower is better for
all metrics, they're all wall clock or cycle counts. The read and write
fault benchmarks just measure fault time, they do not include I/O time.* CONFIG_MEMCG not set:
baseline patched
kbuild 1m25.030000(+-0.088% 3 samples) 1m25.426667(+-0.120% 3 samples)
dd write 100 MiB 0.859211561 +-15.10% 0.874162885 +-15.03%
dd write 200 MiB 1.670653105 +-17.87% 1.669384764 +-11.99%
dd write 1000 MiB 8.434691190 +-14.15% 8.474733215 +-14.77%
read fault cycles 254.0(+-0.000% 10 samples) 253.0(+-0.000% 10 samples)
write fault cycles 2021.2(+-3.070% 10 samples) 1984.5(+-1.036% 10 samples)* CONFIG_MEMCG=y root_memcg:
baseline patched
kbuild 1m25.716667(+-0.105% 3 samples) 1m25.686667(+-0.153% 3 samples)
dd write 100 MiB 0.855650830 +-14.90% 0.887557919 +-14.90%
dd write 200 MiB 1.688322953 +-12.72% 1.667682724 +-13.33%
dd write 1000 MiB 8.418601605 +-14.30% 8.673532299 +-15.00%
read fault cycles 266.0(+-0.000% 10 samples) 266.0(+-0.000% 10 samples)
write fault cycles 2051.7(+-1.349% 10 samples) 2049.6(+-1.686% 10 samples)* CONFIG_MEMCG=y non-root_memcg:
baseline patched
kbuild 1m26.120000(+-0.273% 3 samples) 1m25.763333(+-0.127% 3 samples)
dd write 100 MiB 0.861723964 +-15.25% 0.818129350 +-14.82%
dd write 200 MiB 1.669887569 +-13.30% 1.698645885 +-13.27%
dd write 1000 MiB 8.383191730 +-14.65% 8.351742280 +-14.52%
read fault cycles 265.7(+-0.172% 10 samples) 267.0(+-0.000% 10 samples)
write fault cycles 2070.6(+-1.512% 10 samples) 2084.4(+-2.148% 10 samples)As expected anon page faults are not affected by this patch.
tj: Updated to apply on top of the recent cancel_dirty_page() changes.
Signed-off-by: Sha Zhengju
Signed-off-by: Greg Thelen
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe
16 Apr, 2015
3 commits
-
We converted some of the usages of ACCESS_ONCE to READ_ONCE in the mm/
tree since it doesn't work reliably on non-scalar types.This patch removes the rest of the usages of ACCESS_ONCE, and use the new
READ_ONCE API for the read accesses. This makes things cleaner, instead
of using separate/multiple sets of APIs.Signed-off-by: Jason Low
Acked-by: Michal Hocko
Acked-by: Davidlohr Bueso
Acked-by: Rik van Riel
Reviewed-by: Christian Borntraeger
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Low and high watermarks, as they defined in the TODO to the mem_cgroup
struct, have already been implemented by Johannes, so remove the stale
comment.Signed-off-by: Vladimir Davydov
Cc: Johannes Weiner
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
mem_cgroup_lookup() is a wrapper around mem_cgroup_from_id(), which
checks that id != 0 before issuing the function call. Today, there is
no point in this additional check apart from optimization, because there
is no css with id 0 to css_from_id.Signed-off-by: Vladimir Davydov
Acked-by: Michal Hocko
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
15 Apr, 2015
3 commits
-
If kernel panics due to oom, caused by a cgroup reaching its limit, when
'compulsory panic_on_oom' is enabled, then we will only see that the OOM
happened because of "compulsory panic_on_oom is enabled" but this doesn't
tell the difference between mempolicy and memcg. And dumping system wide
information is plain wrong and more confusing. This patch provides the
information of the cgroup whose limit triggerred panicSigned-off-by: Balasubramani Vivekanandan
Acked-by: Michal Hocko
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When !MMU, it will report warning. The related warning with allmodconfig
under c6x:CC mm/memcontrol.o
mm/memcontrol.c:2802:12: warning: 'mem_cgroup_move_account' defined but not used [-Wunused-function]
static int mem_cgroup_move_account(struct page *page,
^Signed-off-by: Chen Gang
Acked-by: Michal Hocko
Acked-by: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add myself to the list of copyright holders.
Signed-off-by: Johannes Weiner
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 Mar, 2015
1 commit
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If the memory cgroup controller is initially mounted in the scope of the
default cgroup hierarchy and then remounted to a legacy hierarchy, it will
still have hierarchy support enabled, which is incorrect. We should
disable hierarchy support if bound to the legacy cgroup hierarchy.Signed-off-by: Vladimir Davydov
Signed-off-by: Johannes Weiner
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
01 Mar, 2015
2 commits
-
The memcg control knobs indicate the highest possible value using the
symbolic name "infinity", which is long and awkward to type.Switch to the string "max", which is just as descriptive but shorter and
sweeter.This changes a user interface, so do it before the release and before
the development flag is dropped from the default hierarchy.Signed-off-by: Johannes Weiner
Cc: Michal Hocko
Cc: Tejun Heo
Cc: Vladimir Davydov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
A memcg is considered low limited even when the current usage is equal to
the low limit. This leads to interesting side effects e.g.
groups/hierarchies with no memory accounted are considered protected and
so the reclaim will emit MEMCG_LOW event when encountering them.Another and much bigger issue was reported by Joonsoo Kim. He has hit a
NULL ptr dereference with the legacy cgroup API which even doesn't have
low limit exposed. The limit is 0 by default but the initial check fails
for memcg with 0 consumption and parent_mem_cgroup() would return NULL if
use_hierarchy is 0 and so page_counter_read would try to dereference NULL.I suppose that the current implementation is just an overlook because the
documentation in Documentation/cgroups/unified-hierarchy.txt says:"The memory.low boundary on the other hand is a top-down allocated
reserve. A cgroup enjoys reclaim protection when it and all its
ancestors are below their low boundaries"Fix the usage and the low limit comparision in mem_cgroup_low accordingly.
Fixes: 241994ed8649 (mm: memcontrol: default hierarchy interface for memory)
Reported-by: Joonsoo Kim
Signed-off-by: Michal Hocko
Acked-by: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 Feb, 2015
8 commits
-
Move memcg_socket_limit_enabled decrement to tcp_destroy_cgroup (called
from memcg_destroy_kmem -> mem_cgroup_sockets_destroy) and zap a bunch of
wrapper functions.Although this patch moves static keys decrement from __mem_cgroup_free to
mem_cgroup_css_free, it does not introduce any functional changes, because
the keys are incremented on setting the limit (tcp or kmem), which can
only happen after successful mem_cgroup_css_online.Signed-off-by: Vladimir Davydov
Cc: Glauber Costa
Cc: KAMEZAWA Hiroyuki
Cc: Eric W. Biederman
Cc: David S. Miller
Cc: Johannes Weiner
Acked-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Now, the only reason to keep kmemcg_id till css free is list_lru, which
uses it to distribute elements between per-memcg lists. However, it can
be easily sorted out - we only need to change kmemcg_id of an offline
cgroup to its parent's id, making further list_lru_add()'s add elements to
the parent's list, and then move all elements from the offline cgroup's
list to the one of its parent. It will work, because a racing
list_lru_del() does not need to know the list it is deleting the element
from. It can decrement the wrong nr_items counter though, but the ongoing
reparenting will fix it. After list_lru reparenting is done we are free
to release kmemcg_id saving a valuable slot in a per-memcg array for new
cgroups.Signed-off-by: Vladimir Davydov
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Tejun Heo
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Dave Chinner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We need to look up a kmem_cache in ->memcg_params.memcg_caches arrays only
on allocations, so there is no need to have the array entries set until
css free - we can clear them on css offline. This will allow us to reuse
array entries more efficiently and avoid costly array relocations.Signed-off-by: Vladimir Davydov
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Tejun Heo
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Dave Chinner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Currently, kmem_cache stores a pointer to struct memcg_cache_params
instead of embedding it. The rationale is to save memory when kmem
accounting is disabled. However, the memcg_cache_params has shrivelled
drastically since it was first introduced:* Initially:
struct memcg_cache_params {
bool is_root_cache;
union {
struct kmem_cache *memcg_caches[0];
struct {
struct mem_cgroup *memcg;
struct list_head list;
struct kmem_cache *root_cache;
bool dead;
atomic_t nr_pages;
struct work_struct destroy;
};
};
};* Now:
struct memcg_cache_params {
bool is_root_cache;
union {
struct {
struct rcu_head rcu_head;
struct kmem_cache *memcg_caches[0];
};
struct {
struct mem_cgroup *memcg;
struct kmem_cache *root_cache;
};
};
};So the memory saving does not seem to be a clear win anymore.
OTOH, keeping a pointer to memcg_cache_params struct instead of embedding
it results in touching one more cache line on kmem alloc/free hot paths.
Besides, it makes linking kmem caches in a list chained by a field of
struct memcg_cache_params really painful due to a level of indirection,
while I want to make them linked in the following patch. That said, let
us embed it.Signed-off-by: Vladimir Davydov
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Tejun Heo
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Dave Chinner
Cc: Dan Carpenter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There are several FS shrinkers, including super_block::s_shrink, that
keep reclaimable objects in the list_lru structure. Hence to turn them
to memcg-aware shrinkers, it is enough to make list_lru per-memcg.This patch does the trick. It adds an array of lru lists to the
list_lru_node structure (per-node part of the list_lru), one for each
kmem-active memcg, and dispatches every item addition or removal to the
list corresponding to the memcg which the item is accounted to. So now
the list_lru structure is not just per node, but per node and per memcg.Not all list_lrus need this feature, so this patch also adds a new
method, list_lru_init_memcg, which initializes a list_lru as memcg
aware. Otherwise (i.e. if initialized with old list_lru_init), the
list_lru won't have per memcg lists.Just like per memcg caches arrays, the arrays of per-memcg lists are
indexed by memcg_cache_id, so we must grow them whenever
memcg_nr_cache_ids is increased. So we introduce a callback,
memcg_update_all_list_lrus, invoked by memcg_alloc_cache_id if the id
space is full.The locking is implemented in a manner similar to lruvecs, i.e. we have
one lock per node that protects all lists (both global and per cgroup) on
the node.Signed-off-by: Vladimir Davydov
Cc: Dave Chinner
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Greg Thelen
Cc: Glauber Costa
Cc: Alexander Viro
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We need a stable value of memcg_nr_cache_ids in kmem_cache_create()
(memcg_alloc_cache_params() wants it for root caches), where we only
hold the slab_mutex and no memcg-related locks. As a result, we have to
update memcg_nr_cache_ids under the slab_mutex, which we can only take
on the slab's side (see memcg_update_array_size). This looks awkward
and will become even worse when per-memcg list_lru is introduced, which
also wants stable access to memcg_nr_cache_ids.To get rid of this dependency between the memcg_nr_cache_ids and the
slab_mutex, this patch introduces a special rwsem. The rwsem is held
for writing during memcg_caches arrays relocation and memcg_nr_cache_ids
updates. Therefore one can take it for reading to get a stable access
to memcg_caches arrays and/or memcg_nr_cache_ids.Currently the semaphore is taken for reading only from
kmem_cache_create, right before taking the slab_mutex, so right now
there's no much point in using rwsem instead of mutex. However, once
list_lru is made per-memcg it will allow list_lru initializations to
proceed concurrently.Signed-off-by: Vladimir Davydov
Cc: Dave Chinner
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Greg Thelen
Cc: Glauber Costa
Cc: Alexander Viro
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
memcg_limited_groups_array_size, which defines the size of memcg_caches
arrays, sounds rather cumbersome. Also it doesn't point anyhow that
it's related to kmem/caches stuff. So let's rename it to
memcg_nr_cache_ids. It's concise and points us directly to
memcg_cache_id.Also, rename kmem_limited_groups to memcg_cache_ida.
Signed-off-by: Vladimir Davydov
Cc: Dave Chinner
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Greg Thelen
Cc: Glauber Costa
Cc: Alexander Viro
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch adds SHRINKER_MEMCG_AWARE flag. If a shrinker has this flag
set, it will be called per memory cgroup. The memory cgroup to scan
objects from is passed in shrink_control->memcg. If the memory cgroup
is NULL, a memcg aware shrinker is supposed to scan objects from the
global list. Unaware shrinkers are only called on global pressure with
memcg=NULL.Signed-off-by: Vladimir Davydov
Cc: Dave Chinner
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Greg Thelen
Cc: Glauber Costa
Cc: Alexander Viro
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
12 Feb, 2015
8 commits
-
pagewalk.c can handle vma in itself, so we don't have to pass vma via
walk->private. And both of mem_cgroup_count_precharge() and
mem_cgroup_move_charge() do for each vma loop themselves, but now it's
done in pagewalk.c, so let's clean up them.Signed-off-by: Naoya Horiguchi
Acked-by: Johannes Weiner
Cc: "Kirill A. Shutemov"
Cc: Andrea Arcangeli
Cc: Cyrill Gorcunov
Cc: Dave Hansen
Cc: Kirill A. Shutemov
Cc: Pavel Emelyanov
Cc: Benjamin Herrenschmidt
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The swap controller code is scattered all over the file. Gather all
the code that isn't directly needed by the memory controller at the
end of the file in its own CONFIG_MEMCG_SWAP section.Signed-off-by: Johannes Weiner
Cc: Michal Hocko
Reviewed-by: Vladimir Davydov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The initialization code for the per-cpu charge stock and the soft
limit tree is compact enough to inline it into mem_cgroup_init().Signed-off-by: Johannes Weiner
Acked-by: Michal Hocko
Reviewed-by: Vladimir Davydov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
- No need to test the node for N_MEMORY. node_online() is enough for
node fallback to work in slab, use NUMA_NO_NODE for everything else.- Remove the BUG_ON() for allocation failure. A NULL pointer crash is
just as descriptive, and the absent return value check is obvious.- Move local variables to the inner-most blocks.
- Point to the tree structure after its initialized, not before, it's
just more logical that way.Signed-off-by: Johannes Weiner
Cc: Michal Hocko
Cc: Vladimir Davydov
Cc: Guenter Roeck
Cc: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Commit 5695be142e20 ("OOM, PM: OOM killed task shouldn't escape PM
suspend") has left a race window when OOM killer manages to
note_oom_kill after freeze_processes checks the counter. The race
window is quite small and really unlikely and partial solution deemed
sufficient at the time of submission.Tejun wasn't happy about this partial solution though and insisted on a
full solution. That requires the full OOM and freezer's task freezing
exclusion, though. This is done by this patch which introduces oom_sem
RW lock and turns oom_killer_disable() into a full OOM barrier.oom_killer_disabled check is moved from the allocation path to the OOM
level and we take oom_sem for reading for both the check and the whole
OOM invocation.oom_killer_disable() takes oom_sem for writing so it waits for all
currently running OOM killer invocations. Then it disable all the further
OOMs by setting oom_killer_disabled and checks for any oom victims.
Victims are counted via mark_tsk_oom_victim resp. unmark_oom_victim. The
last victim wakes up all waiters enqueued by oom_killer_disable().
Therefore this function acts as the full OOM barrier.The page fault path is covered now as well although it was assumed to be
safe before. As per Tejun, "We used to have freezing points deep in file
system code which may be reacheable from page fault." so it would be
better and more robust to not rely on freezing points here. Same applies
to the memcg OOM killer.out_of_memory tells the caller whether the OOM was allowed to trigger and
the callers are supposed to handle the situation. The page allocation
path simply fails the allocation same as before. The page fault path will
retry the fault (more on that later) and Sysrq OOM trigger will simply
complain to the log.Normally there wouldn't be any unfrozen user tasks after
try_to_freeze_tasks so the function will not block. But if there was an
OOM killer racing with try_to_freeze_tasks and the OOM victim didn't
finish yet then we have to wait for it. This should complete in a finite
time, though, because- the victim cannot loop in the page fault handler (it would die
on the way out from the exception)
- it cannot loop in the page allocator because all the further
allocation would fail and __GFP_NOFAIL allocations are not
acceptable at this stage
- it shouldn't be blocked on any locks held by frozen tasks
(try_to_freeze expects lockless context) and kernel threads and
work queues are not frozen yetSigned-off-by: Michal Hocko
Suggested-by: Tejun Heo
Cc: David Rientjes
Cc: Johannes Weiner
Cc: Oleg Nesterov
Cc: Cong Wang
Cc: "Rafael J. Wysocki"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patchset addresses a race which was described in the changelog for
5695be142e20 ("OOM, PM: OOM killed task shouldn't escape PM suspend"):: PM freezer relies on having all tasks frozen by the time devices are
: getting frozen so that no task will touch them while they are getting
: frozen. But OOM killer is allowed to kill an already frozen task in order
: to handle OOM situtation. In order to protect from late wake ups OOM
: killer is disabled after all tasks are frozen. This, however, still keeps
: a window open when a killed task didn't manage to die by the time
: freeze_processes finishes.The original patch hasn't closed the race window completely because that
would require a more complex solution as it can be seen by this patchset.The primary motivation was to close the race condition between OOM killer
and PM freezer _completely_. As Tejun pointed out, even though the race
condition is unlikely the harder it would be to debug weird bugs deep in
the PM freezer when the debugging options are reduced considerably. I can
only speculate what might happen when a task is still runnable
unexpectedly.On a plus side and as a side effect the oom enable/disable has a better
(full barrier) semantic without polluting hot paths.I have tested the series in KVM with 100M RAM:
- many small tasks (20M anon mmap) which are triggering OOM continually
- s2ram which resumes automatically is triggered in a loop
echo processors > /sys/power/pm_test
while true
do
echo mem > /sys/power/state
sleep 1s
done
- simple module which allocates and frees 20M in 8K chunks. If it sees
freezing(current) then it tries another round of allocation before calling
try_to_freeze
- debugging messages of PM stages and OOM killer enable/disable/fail added
and unmark_oom_victim is delayed by 1s after it clears TIF_MEMDIE and before
it wakes up waiters.
- rebased on top of the current mmotm which means some necessary updates
in mm/oom_kill.c. mark_tsk_oom_victim is now called under task_lock but
I think this should be OK because __thaw_task shouldn't interfere with any
locking down wake_up_process. Oleg?As expected there are no OOM killed tasks after oom is disabled and
allocations requested by the kernel thread are failing after all the tasks
are frozen and OOM disabled. I wasn't able to catch a race where
oom_killer_disable would really have to wait but I kinda expected the race
is really unlikely.[ 242.609330] Killed process 2992 (mem_eater) total-vm:24412kB, anon-rss:2164kB, file-rss:4kB
[ 243.628071] Unmarking 2992 OOM victim. oom_victims: 1
[ 243.636072] (elapsed 2.837 seconds) done.
[ 243.641985] Trying to disable OOM killer
[ 243.643032] Waiting for concurent OOM victims
[ 243.644342] OOM killer disabled
[ 243.645447] Freezing remaining freezable tasks ... (elapsed 0.005 seconds) done.
[ 243.652983] Suspending console(s) (use no_console_suspend to debug)
[ 243.903299] kmem_eater: page allocation failure: order:1, mode:0x204010
[...]
[ 243.992600] PM: suspend of devices complete after 336.667 msecs
[ 243.993264] PM: late suspend of devices complete after 0.660 msecs
[ 243.994713] PM: noirq suspend of devices complete after 1.446 msecs
[ 243.994717] ACPI: Preparing to enter system sleep state S3
[ 243.994795] PM: Saving platform NVS memory
[ 243.994796] Disabling non-boot CPUs ...The first 2 patches are simple cleanups for OOM. They should go in
regardless the rest IMO.Patches 3 and 4 are trivial printk -> pr_info conversion and they should
go in ditto.The main patch is the last one and I would appreciate acks from Tejun and
Rafael. I think the OOM part should be OK (except for __thaw_task vs.
task_lock where a look from Oleg would appreciated) but I am not so sure I
haven't screwed anything in the freezer code. I have found several
surprises there.This patch (of 5):
This patch is just a preparatory and it doesn't introduce any functional
change.Note:
I am utterly unhappy about lowmemory killer abusing TIF_MEMDIE just to
wait for the oom victim and to prevent from new killing. This is
just a side effect of the flag. The primary meaning is to give the oom
victim access to the memory reserves and that shouldn't be necessary
here.Signed-off-by: Michal Hocko
Cc: Tejun Heo
Cc: David Rientjes
Cc: Johannes Weiner
Cc: Oleg Nesterov
Cc: Cong Wang
Cc: "Rafael J. Wysocki"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Turn the move type enum into flags and give the flags field a shorter
name. Once that is done, move_anon() and move_file() are simple enough to
just fold them into the callsites.[akpm@linux-foundation.org: tweak MOVE_MASK definition, per Michal]
Signed-off-by: Johannes Weiner
Acked-by: Michal Hocko
Reviewed-by: Vladimir Davydov
Cc: Greg Thelen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Introduce the basic control files to account, partition, and limit
memory using cgroups in default hierarchy mode.This interface versioning allows us to address fundamental design
issues in the existing memory cgroup interface, further explained
below. The old interface will be maintained indefinitely, but a
clearer model and improved workload performance should encourage
existing users to switch over to the new one eventually.The control files are thus:
- memory.current shows the current consumption of the cgroup and its
descendants, in bytes.- memory.low configures the lower end of the cgroup's expected
memory consumption range. The kernel considers memory below that
boundary to be a reserve - the minimum that the workload needs in
order to make forward progress - and generally avoids reclaiming
it, unless there is an imminent risk of entering an OOM situation.- memory.high configures the upper end of the cgroup's expected
memory consumption range. A cgroup whose consumption grows beyond
this threshold is forced into direct reclaim, to work off the
excess and to throttle new allocations heavily, but is generally
allowed to continue and the OOM killer is not invoked.- memory.max configures the hard maximum amount of memory that the
cgroup is allowed to consume before the OOM killer is invoked.- memory.events shows event counters that indicate how often the
cgroup was reclaimed while below memory.low, how often it was
forced to reclaim excess beyond memory.high, how often it hit
memory.max, and how often it entered OOM due to memory.max. This
allows users to identify configuration problems when observing a
degradation in workload performance. An overcommitted system will
have an increased rate of low boundary breaches, whereas increased
rates of high limit breaches, maximum hits, or even OOM situations
will indicate internally overcommitted cgroups.For existing users of memory cgroups, the following deviations from
the current interface are worth pointing out and explaining:- The original lower boundary, the soft limit, is defined as a limit
that is per default unset. As a result, the set of cgroups that
global reclaim prefers is opt-in, rather than opt-out. The costs
for optimizing these mostly negative lookups are so high that the
implementation, despite its enormous size, does not even provide
the basic desirable behavior. First off, the soft limit has no
hierarchical meaning. All configured groups are organized in a
global rbtree and treated like equal peers, regardless where they
are located in the hierarchy. This makes subtree delegation
impossible. Second, the soft limit reclaim pass is so aggressive
that it not just introduces high allocation latencies into the
system, but also impacts system performance due to overreclaim, to
the point where the feature becomes self-defeating.The memory.low boundary on the other hand is a top-down allocated
reserve. A cgroup enjoys reclaim protection when it and all its
ancestors are below their low boundaries, which makes delegation
of subtrees possible. Secondly, new cgroups have no reserve per
default and in the common case most cgroups are eligible for the
preferred reclaim pass. This allows the new low boundary to be
efficiently implemented with just a minor addition to the generic
reclaim code, without the need for out-of-band data structures and
reclaim passes. Because the generic reclaim code considers all
cgroups except for the ones running low in the preferred first
reclaim pass, overreclaim of individual groups is eliminated as
well, resulting in much better overall workload performance.- The original high boundary, the hard limit, is defined as a strict
limit that can not budge, even if the OOM killer has to be called.
But this generally goes against the goal of making the most out of
the available memory. The memory consumption of workloads varies
during runtime, and that requires users to overcommit. But doing
that with a strict upper limit requires either a fairly accurate
prediction of the working set size or adding slack to the limit.
Since working set size estimation is hard and error prone, and
getting it wrong results in OOM kills, most users tend to err on
the side of a looser limit and end up wasting precious resources.The memory.high boundary on the other hand can be set much more
conservatively. When hit, it throttles allocations by forcing
them into direct reclaim to work off the excess, but it never
invokes the OOM killer. As a result, a high boundary that is
chosen too aggressively will not terminate the processes, but
instead it will lead to gradual performance degradation. The user
can monitor this and make corrections until the minimal memory
footprint that still gives acceptable performance is found.In extreme cases, with many concurrent allocations and a complete
breakdown of reclaim progress within the group, the high boundary
can be exceeded. But even then it's mostly better to satisfy the
allocation from the slack available in other groups or the rest of
the system than killing the group. Otherwise, memory.max is there
to limit this type of spillover and ultimately contain buggy or
even malicious applications.- The original control file names are unwieldy and inconsistent in
many different ways. For example, the upper boundary hit count is
exported in the memory.failcnt file, but an OOM event count has to
be manually counted by listening to memory.oom_control events, and
lower boundary / soft limit events have to be counted by first
setting a threshold for that value and then counting those events.
Also, usage and limit files encode their units in the filename.
That makes the filenames very long, even though this is not
information that a user needs to be reminded of every time they
type out those names.To address these naming issues, as well as to signal clearly that
the new interface carries a new configuration model, the naming
conventions in it necessarily differ from the old interface.- The original limit files indicate the state of an unset limit with
a very high number, and a configured limit can be unset by echoing
-1 into those files. But that very high number is implementation
and architecture dependent and not very descriptive. And while -1
can be understood as an underflow into the highest possible value,
-2 or -10M etc. do not work, so it's not inconsistent.memory.low, memory.high, and memory.max will use the string
"infinity" to indicate and set the highest possible value.[akpm@linux-foundation.org: use seq_puts() for basic strings]
Signed-off-by: Johannes Weiner
Acked-by: Michal Hocko
Cc: Vladimir Davydov
Cc: Greg Thelen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
