13 Jan, 2012
1 commit
-
Signed-off-by: Johannes Weiner
Acked-by: David Rientjes
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Michal Hocko
Cc: Balbir Singh
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Jan, 2012
1 commit
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migrate was doing an rmap_walk with speculative lock-less access on
pagetables. That could lead it to not serializing properly against mremap
PT locks. But a second problem remains in the order of vmas in the
same_anon_vma list used by the rmap_walk.If vma_merge succeeds in copy_vma, the src vma could be placed after the
dst vma in the same_anon_vma list. That could still lead to migrate
missing some pte.This patch adds an anon_vma_moveto_tail() function to force the dst vma at
the end of the list before mremap starts to solve the problem.If the mremap is very large and there are a lots of parents or childs
sharing the anon_vma root lock, this should still scale better than taking
the anon_vma root lock around every pte copy practically for the whole
duration of mremap.Update: Hugh noticed special care is needed in the error path where
move_page_tables goes in the reverse direction, a second
anon_vma_moveto_tail() call is needed in the error path.This program exercises the anon_vma_moveto_tail:
===
int main()
{
static struct timeval oldstamp, newstamp;
long diffsec;
char *p, *p2, *p3, *p4;
if (posix_memalign((void **)&p, 2*1024*1024, SIZE))
perror("memalign"), exit(1);
if (posix_memalign((void **)&p2, 2*1024*1024, SIZE))
perror("memalign"), exit(1);
if (posix_memalign((void **)&p3, 2*1024*1024, SIZE))
perror("memalign"), exit(1);memset(p, 0xff, SIZE);
printf("%p\n", p);
memset(p2, 0xff, SIZE);
memset(p3, 0x77, 4096);
if (memcmp(p, p2, SIZE))
printf("error\n");
p4 = mremap(p+SIZE/2, SIZE/2, SIZE/2, MREMAP_FIXED|MREMAP_MAYMOVE, p3);
if (p4 != p3)
perror("mremap"), exit(1);
p4 = mremap(p4, SIZE/2, SIZE/2, MREMAP_FIXED|MREMAP_MAYMOVE, p+SIZE/2);
if (p4 != p+SIZE/2)
perror("mremap"), exit(1);
if (memcmp(p, p2, SIZE))
printf("error\n");
printf("ok\n");return 0;
}
===$ perf probe -a anon_vma_moveto_tail
Add new event:
probe:anon_vma_moveto_tail (on anon_vma_moveto_tail)You can now use it on all perf tools, such as:
perf record -e probe:anon_vma_moveto_tail -aR sleep 1
$ perf record -e probe:anon_vma_moveto_tail -aR ./anon_vma_moveto_tail
0x7f2ca2800000
ok
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.043 MB perf.data (~1860 samples) ]
$ perf report --stdio
100.00% anon_vma_moveto [kernel.kallsyms] [k] anon_vma_moveto_tailSigned-off-by: Andrea Arcangeli
Reported-by: Nai Xia
Acked-by: Mel Gorman
Cc: Hugh Dickins
Cc: Pawel Sikora
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Nov, 2011
1 commit
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* 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits)
Revert "tracing: Include module.h in define_trace.h"
irq: don't put module.h into irq.h for tracking irqgen modules.
bluetooth: macroize two small inlines to avoid module.h
ip_vs.h: fix implicit use of module_get/module_put from module.h
nf_conntrack.h: fix up fallout from implicit moduleparam.h presence
include: replace linux/module.h with "struct module" wherever possible
include: convert various register fcns to macros to avoid include chaining
crypto.h: remove unused crypto_tfm_alg_modname() inline
uwb.h: fix implicit use of asm/page.h for PAGE_SIZE
pm_runtime.h: explicitly requires notifier.h
linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h
miscdevice.h: fix up implicit use of lists and types
stop_machine.h: fix implicit use of smp.h for smp_processor_id
of: fix implicit use of errno.h in include/linux/of.h
of_platform.h: delete needless include
acpi: remove module.h include from platform/aclinux.h
miscdevice.h: delete unnecessary inclusion of module.h
device_cgroup.h: delete needless include
net: sch_generic remove redundant use of
net: inet_timewait_sock doesnt need
...Fix up trivial conflicts (other header files, and removal of the ab3550 mfd driver) in
- drivers/media/dvb/frontends/dibx000_common.c
- drivers/media/video/{mt9m111.c,ov6650.c}
- drivers/mfd/ab3550-core.c
- include/linux/dmaengine.h
01 Nov, 2011
1 commit
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try_to_unmap_one() is called by try_to_unmap_ksm(), too.
Signed-off-by: Wanlong Gao
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
31 Oct, 2011
1 commit
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The files changed within are only using the EXPORT_SYMBOL
macro variants. They are not using core modular infrastructure
and hence don't need module.h but only the export.h header.Signed-off-by: Paul Gortmaker
27 Jul, 2011
1 commit
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* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/writeback: (27 commits)
mm: properly reflect task dirty limits in dirty_exceeded logic
writeback: don't busy retry writeback on new/freeing inodes
writeback: scale IO chunk size up to half device bandwidth
writeback: trace global_dirty_state
writeback: introduce max-pause and pass-good dirty limits
writeback: introduce smoothed global dirty limit
writeback: consolidate variable names in balance_dirty_pages()
writeback: show bdi write bandwidth in debugfs
writeback: bdi write bandwidth estimation
writeback: account per-bdi accumulated written pages
writeback: make writeback_control.nr_to_write straight
writeback: skip tmpfs early in balance_dirty_pages_ratelimited_nr()
writeback: trace event writeback_queue_io
writeback: trace event writeback_single_inode
writeback: remove .nonblocking and .encountered_congestion
writeback: remove writeback_control.more_io
writeback: skip balance_dirty_pages() for in-memory fs
writeback: add bdi_dirty_limit() kernel-doc
writeback: avoid extra sync work at enqueue time
writeback: elevate queue_io() into wb_writeback()
...Fix up trivial conflicts in fs/fs-writeback.c and mm/filemap.c
24 Jul, 2011
1 commit
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On x86 a page without a mapper is by definition not referenced / old.
The s390 architecture keeps the reference bit in the storage key and
the current code will check the storage key for page without a mapper.
This leads to an interesting effect: the first time an s390 system
needs to write pages to swap it only finds referenced pages. This
causes a lot of pages to get added and written to the swap device.
To avoid this behaviour change page_referenced to query the storage
key only if there is a mapper of the page.Signed-off-by: Martin Schwidefsky
21 Jul, 2011
1 commit
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i_alloc_sem is a rather special rw_semaphore. It's the last one that may
be released by a non-owner, and it's write side is always mirrored by
real exclusion. It's intended use it to wait for all pending direct I/O
requests to finish before starting a truncate.Replace it with a hand-grown construct:
- exclusion for truncates is already guaranteed by i_mutex, so it can
simply fall way
- the reader side is replaced by an i_dio_count member in struct inode
that counts the number of pending direct I/O requests. Truncate can't
proceed as long as it's non-zero
- when i_dio_count reaches non-zero we wake up a pending truncate using
wake_up_bit on a new bit in i_flags
- new references to i_dio_count can't appear while we are waiting for
it to read zero because the direct I/O count always needs i_mutex
(or an equivalent like XFS's i_iolock) for starting a new operation.This scheme is much simpler, and saves the space of a spinlock_t and a
struct list_head in struct inode (typically 160 bits on a non-debug 64-bit
system).Signed-off-by: Christoph Hellwig
Signed-off-by: Al Viro
28 Jun, 2011
1 commit
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We cannot take a mutex while holding a spinlock, so flip the order and
fix the locking documentation.Signed-off-by: Peter Zijlstra
Acked-by: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Jun, 2011
3 commits
-
Hugh Dickins points out that lockdep (correctly) spots a potential
deadlock on the anon_vma lock, because we now do a GFP_KERNEL allocation
of anon_vma_chain while doing anon_vma_clone(). The problem is that
page reclaim will want to take the anon_vma lock of any anonymous pages
that it will try to reclaim.So re-organize the code in anon_vma_clone() slightly: first do just a
GFP_NOWAIT allocation, which will usually work fine. But if that fails,
let's just drop the lock and re-do the allocation, now with GFP_KERNEL.End result: not only do we avoid the locking problem, this also ends up
getting better concurrency in case the allocation does need to block.
Tim Chen reports that with all these anon_vma locking tweaks, we're now
almost back up to the spinlock performance.Reported-and-tested-by: Hugh Dickins
Tested-by: Tim Chen
Cc: Peter Zijlstra
Cc: Andi Kleen
Signed-off-by: Linus Torvalds -
This matches the anon_vma_clone() case, and uses the same lock helper
functions. Because of the need to potentially release the anon_vma's,
it's a bit more complex, though.We traverse the 'vma->anon_vma_chain' in two phases: the first loop gets
the anon_vma lock (with the helper function that only takes the lock
once for the whole loop), and removes any entries that don't need any
more processing.The second phase just traverses the remaining list entries (without
holding the anon_vma lock), and does any actual freeing of the
anon_vma's that is required.Signed-off-by: Peter Zijlstra
Tested-by: Hugh Dickins
Tested-by: Tim Chen
Cc: Andi Kleen
Signed-off-by: Linus Torvalds -
In anon_vma_clone() we traverse the vma->anon_vma_chain of the source
vma, locking the anon_vma for each entry.But they are all going to have the same root entry, which means that
we're locking and unlocking the same lock over and over again. Which is
expensive in locked operations, but can get _really_ expensive when that
root entry sees any kind of lock contention.In fact, Tim Chen reports a big performance regression due to this: when
we switched to use a mutex instead of a spinlock, the contention case
gets much worse.So to alleviate this all, this commit creates a small helper function
(lock_anon_vma_root()) that can be used to take the lock just once
rather than taking and releasing it over and over again.We still have the same "take the lock and release" it behavior in the
exit path (in unlink_anon_vmas()), but that one is a bit harder to fix
since we're actually freeing the anon_vma entries as we go, and that
will touch the lock too.Reported-and-tested-by: Tim Chen
Tested-by: Hugh Dickins
Cc: Peter Zijlstra
Cc: Andi Kleen
Signed-off-by: Linus Torvalds
08 Jun, 2011
1 commit
-
Split the global inode_wb_list_lock into a per-bdi_writeback list_lock,
as it's currently the most contended lock in the system for metadata
heavy workloads. It won't help for single-filesystem workloads for
which we'll need the I/O-less balance_dirty_pages, but at least we
can dedicate a cpu to spinning on each bdi now for larger systems.Based on earlier patches from Nick Piggin and Dave Chinner.
It reduces lock contentions to 1/4 in this test case:
10 HDD JBOD, 100 dd on each disk, XFS, 6GB ramlock_stat version 0.3
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
class name con-bounces contentions waittime-min waittime-max waittime-total acq-bounces acquisitions holdtime-min holdtime-max holdtime-total
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
vanilla 2.6.39-rc3:
inode_wb_list_lock: 42590 44433 0.12 147.74 144127.35 252274 886792 0.08 121.34 917211.23
------------------
inode_wb_list_lock 2 [] bdev_inode_switch_bdi+0x29/0x85
inode_wb_list_lock 34 [] inode_wb_list_del+0x22/0x49
inode_wb_list_lock 12893 [] __mark_inode_dirty+0x170/0x1d0
inode_wb_list_lock 10702 [] writeback_single_inode+0x16d/0x20a
------------------
inode_wb_list_lock 2 [] bdev_inode_switch_bdi+0x29/0x85
inode_wb_list_lock 19 [] inode_wb_list_del+0x22/0x49
inode_wb_list_lock 5550 [] __mark_inode_dirty+0x170/0x1d0
inode_wb_list_lock 8511 [] writeback_sb_inodes+0x10f/0x1572.6.39-rc3 + patch:
&(&wb->list_lock)->rlock: 11383 11657 0.14 151.69 40429.51 90825 527918 0.11 145.90 556843.37
------------------------
&(&wb->list_lock)->rlock 10 [] inode_wb_list_del+0x5f/0x86
&(&wb->list_lock)->rlock 1493 [] writeback_inodes_wb+0x3d/0x150
&(&wb->list_lock)->rlock 3652 [] writeback_sb_inodes+0x123/0x16f
&(&wb->list_lock)->rlock 1412 [] writeback_single_inode+0x17f/0x223
------------------------
&(&wb->list_lock)->rlock 3 [] bdi_lock_two+0x46/0x4b
&(&wb->list_lock)->rlock 6 [] inode_wb_list_del+0x5f/0x86
&(&wb->list_lock)->rlock 2061 [] __mark_inode_dirty+0x173/0x1cf
&(&wb->list_lock)->rlock 2629 [] writeback_sb_inodes+0x123/0x16fhughd@google.com: fix recursive lock when bdi_lock_two() is called with new the same as old
akpm@linux-foundation.org: cleanup bdev_inode_switch_bdi() commentSigned-off-by: Christoph Hellwig
Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Wu Fengguang
30 May, 2011
1 commit
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Inspired by an analysis from Hugh on why again all this doesn't explode
in our face.Signed-off-by: Peter Zijlstra
Signed-off-by: Linus Torvalds
29 May, 2011
2 commits
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On one machine I've been getting hangs, a page fault's anon_vma_prepare()
waiting in anon_vma_lock(), other processes waiting for that page's lock.This is a replay of last year's f18194275c39 "mm: fix hang on
anon_vma->root->lock".The new page_lock_anon_vma() places too much faith in its refcount: when
it has acquired the mutex_trylock(), it's possible that a racing task in
anon_vma_alloc() has just reallocated the struct anon_vma, set refcount
to 1, and is about to reset its anon_vma->root.Fix this by saving anon_vma->root, and relying on the usual page_mapped()
check instead of a refcount check: if page is still mapped, the anon_vma
is still ours; if page is not still mapped, we're no longer interested.Signed-off-by: Hugh Dickins
Signed-off-by: Linus Torvalds -
I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap()
just once. The stack showed khugepaged allocation trying to compact
pages: the call to page_add_anon_rmap() coming from remove_migration_pte().That path holds anon_vma lock, but does not hold mmap_sem: it can
therefore race with a split_vma(), and in commit 5f70b962ccc2 "mmap:
avoid unnecessary anon_vma lock" we just took away the anon_vma lock
protection when adjusting vma->vm_end.I don't think that particular BUG_ON ever caught anything interesting,
so better replace it by a comment, than reinstate the anon_vma locking.Signed-off-by: Hugh Dickins
Signed-off-by: Linus Torvalds
25 May, 2011
6 commits
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Optimize the page_lock_anon_vma() fast path to be one atomic op, instead
of two.Signed-off-by: Peter Zijlstra
Reviewed-by: KAMEZAWA Hiroyuki
Cc: Benjamin Herrenschmidt
Cc: David Miller
Cc: Martin Schwidefsky
Cc: Russell King
Cc: Paul Mundt
Cc: Jeff Dike
Cc: Richard Weinberger
Cc: Tony Luck
Cc: Hugh Dickins
Cc: Mel Gorman
Cc: KOSAKI Motohiro
Cc: Nick Piggin
Cc: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Straightforward conversion of anon_vma->lock to a mutex.
Signed-off-by: Peter Zijlstra
Acked-by: Hugh Dickins
Reviewed-by: KOSAKI Motohiro
Cc: Benjamin Herrenschmidt
Cc: David Miller
Cc: Martin Schwidefsky
Cc: Russell King
Cc: Paul Mundt
Cc: Jeff Dike
Cc: Richard Weinberger
Cc: Tony Luck
Cc: KAMEZAWA Hiroyuki
Cc: Mel Gorman
Cc: Nick Piggin
Cc: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Convert page_lock_anon_vma() over to use refcounts. This is done to
prepare for the conversion of anon_vma from spinlock to mutex.Sadly this inceases the cost of page_lock_anon_vma() from one to two
atomics, a follow up patch addresses this, lets keep that simple for now.Signed-off-by: Peter Zijlstra
Reviewed-by: KAMEZAWA Hiroyuki
Reviewed-by: KOSAKI Motohiro
Acked-by: Hugh Dickins
Cc: Benjamin Herrenschmidt
Cc: David Miller
Cc: Martin Schwidefsky
Cc: Russell King
Cc: Paul Mundt
Cc: Jeff Dike
Cc: Richard Weinberger
Cc: Tony Luck
Cc: Mel Gorman
Cc: Nick Piggin
Cc: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
A slightly more verbose comment to go along with the trickery in
page_lock_anon_vma().Signed-off-by: Peter Zijlstra
Reviewed-by: KOSAKI Motohiro
Reviewed-by: KAMEZAWA Hiroyuki
Acked-by: Mel Gorman
Acked-by: Hugh Dickins
Cc: Benjamin Herrenschmidt
Cc: David Miller
Cc: Martin Schwidefsky
Cc: Russell King
Cc: Paul Mundt
Cc: Jeff Dike
Cc: Richard Weinberger
Cc: Tony Luck
Cc: Nick Piggin
Cc: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Its beyond ugly and gets in the way.
Signed-off-by: Peter Zijlstra
Acked-by: Hugh Dickins
Cc: Benjamin Herrenschmidt
Cc: David Miller
Cc: Martin Schwidefsky
Cc: Russell King
Cc: Paul Mundt
Cc: Jeff Dike
Cc: Richard Weinberger
Cc: Tony Luck
Cc: KAMEZAWA Hiroyuki
Cc: Mel Gorman
Cc: Namhyung Kim
Cc: KOSAKI Motohiro
Cc: Nick Piggin
Cc: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Straightforward conversion of i_mmap_lock to a mutex.
Signed-off-by: Peter Zijlstra
Acked-by: Hugh Dickins
Cc: Benjamin Herrenschmidt
Cc: David Miller
Cc: Martin Schwidefsky
Cc: Russell King
Cc: Paul Mundt
Cc: Jeff Dike
Cc: Richard Weinberger
Cc: Tony Luck
Cc: KAMEZAWA Hiroyuki
Cc: Mel Gorman
Cc: KOSAKI Motohiro
Cc: Nick Piggin
Cc: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 May, 2011
1 commit
-
The page_clear_dirty primitive always sets the default storage key
which resets the access control bits and the fetch protection bit.
That will surprise a KVM guest that sets non-zero access control
bits or the fetch protection bit. Merge page_test_dirty and
page_clear_dirty back to a single function and only clear the
dirty bit from the storage key.In addition move the function page_test_and_clear_dirty and
page_test_and_clear_young to page.h where they belong. This
requires to change the parameter from a struct page * to a page
frame number.Signed-off-by: Martin Schwidefsky
25 Mar, 2011
2 commits
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Protect the inode writeback list with a new global lock
inode_wb_list_lock and use it to protect the list manipulations and
traversals. This lock replaces the inode_lock as the inodes on the
list can be validity checked while holding the inode->i_lock and
hence the inode_lock is no longer needed to protect the list.Signed-off-by: Dave Chinner
Signed-off-by: Al Viro -
Protect inode state transitions and validity checks with the
inode->i_lock. This enables us to make inode state transitions
independently of the inode_lock and is the first step to peeling
away the inode_lock from the code.This requires that __iget() is done atomically with i_state checks
during list traversals so that we don't race with another thread
marking the inode I_FREEING between the state check and grabbing the
reference.Also remove the unlock_new_inode() memory barrier optimisation
required to avoid taking the inode_lock when clearing I_NEW.
Simplify the code by simply taking the inode->i_lock around the
state change and wakeup. Because the wakeup is no longer tricky,
remove the wake_up_inode() function and open code the wakeup where
necessary.Signed-off-by: Dave Chinner
Signed-off-by: Al Viro
23 Mar, 2011
3 commits
-
This patch changes the anon_vma refcount to be 0 when the object is free.
It does this by adding 1 ref to being in use in the anon_vma structure
(iow. the anon_vma->head list is not empty).This allows a simpler release scheme without having to check both the
refcount and the list as well as avoids taking a ref for each entry on the
list.Signed-off-by: Peter Zijlstra
Reviewed-by: KAMEZAWA Hiroyuki
Acked-by: Hugh Dickins
Acked-by: Mel Gorman
Acked-by: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We need the anon_vma refcount unconditionally to simplify the anon_vma
lifetime rules.Signed-off-by: Peter Zijlstra
Acked-by: Mel Gorman
Reviewed-by: KAMEZAWA Hiroyuki
Acked-by: Hugh Dickins
Acked-by: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The normal code pattern used in the kernel is: get/put.
Signed-off-by: Peter Zijlstra
Reviewed-by: KAMEZAWA Hiroyuki
Acked-by: Hugh Dickins
Reviewed-by: Rik van Riel
Acked-by: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
14 Mar, 2011
1 commit
-
When vmscan.c calls page_referenced(), if an anon page was created
before a process forked, rmap will search for it in both of the
processes, even though one of them might have since broken COW.If the child process mlocks the vma where the COWed page belongs to,
page_referenced() running on the page mapped by the parent would lead to
*vm_flags getting VM_LOCKED set erroneously (leading to the references
on the parent page being ignored and evicting the parent page too
early).*mapcount would also be decremented by page_referenced_one even if the
page wasn't found by page_check_address.This also lets pmdp_clear_flush_young_notify() go ahead on a
pmd_trans_splitting() pmd.We hold the page_table_lock so __split_huge_page_map() must wait the
pmdp_clear_flush_young_notify() to complete before it can modify the
pmd. The pmd is also still mapped in userland so the young bit may
materialize through a tlb miss before split_huge_page_map runs.This will provide a more accurate page_referenced() behavior during
split_huge_page().Signed-off-by: Andrea Arcangeli
Reported-by: Michel Lespinasse
Reviewed-by: Michel Lespinasse
Reviewed-by: Minchan Kim
Reviewed-by: Johannes Weiner
Reviewed-by: Rik van Riel
Reviewed-by: KOSAKI Motohiro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
14 Jan, 2011
6 commits
-
Replace usage of the mem_cgroup_update_file_mapped() memcg
statistic update routine with two new routines:
* mem_cgroup_inc_page_stat()
* mem_cgroup_dec_page_stat()As before, only the file_mapped statistic is managed. However, these more
general interfaces allow for new statistics to be more easily added. New
statistics are added with memcg dirty page accounting.Signed-off-by: Greg Thelen
Signed-off-by: Andrea Righi
Acked-by: KAMEZAWA Hiroyuki
Acked-by: Daisuke Nishimura
Cc: Balbir Singh
Cc: Minchan Kim
Cc: Wu Fengguang
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
hugetlbfs was changed to allow memory failure to migrate the hugetlbfs
pages and that broke THP as split_huge_page was then called on hugetlbfs
pages too.compound_head/order was also run unsafe on THP pages that can be splitted
at any time.All compound_head() invocations in memory-failure.c that are run on pages
that aren't pinned and that can be freed and reused from under us (while
compound_head is running) are buggy because compound_head can return a
dangling pointer, but I'm not fixing this as this is a generic
memory-failure bug not specific to THP but it applies to hugetlbfs too, so
I can fix it later after THP is merged upstream.Signed-off-by: Andrea Arcangeli
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add hugepage stat information to /proc/vmstat and /proc/meminfo.
Signed-off-by: Andrea Arcangeli
Acked-by: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This documents how split_huge_page is safe vs new vma inserctions into the
anon_vma that may have already released the anon_vma->lock but not
established pmds yet when split_huge_page starts.Signed-off-by: Andrea Arcangeli
Acked-by: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Lately I've been working to make KVM use hugepages transparently without
the usual restrictions of hugetlbfs. Some of the restrictions I'd like to
see removed:1) hugepages have to be swappable or the guest physical memory remains
locked in RAM and can't be paged out to swap2) if a hugepage allocation fails, regular pages should be allocated
instead and mixed in the same vma without any failure and without
userland noticing3) if some task quits and more hugepages become available in the
buddy, guest physical memory backed by regular pages should be
relocated on hugepages automatically in regions under
madvise(MADV_HUGEPAGE) (ideally event driven by waking up the
kernel deamon if the order=HPAGE_PMD_SHIFT-PAGE_SHIFT list becomes
not null)4) avoidance of reservation and maximization of use of hugepages whenever
possible. Reservation (needed to avoid runtime fatal faliures) may be ok for
1 machine with 1 database with 1 database cache with 1 database cache size
known at boot time. It's definitely not feasible with a virtualization
hypervisor usage like RHEV-H that runs an unknown number of virtual machines
with an unknown size of each virtual machine with an unknown amount of
pagecache that could be potentially useful in the host for guest not using
O_DIRECT (aka cache=off).hugepages in the virtualization hypervisor (and also in the guest!) are
much more important than in a regular host not using virtualization,
becasue with NPT/EPT they decrease the tlb-miss cacheline accesses from 24
to 19 in case only the hypervisor uses transparent hugepages, and they
decrease the tlb-miss cacheline accesses from 19 to 15 in case both the
linux hypervisor and the linux guest both uses this patch (though the
guest will limit the addition speedup to anonymous regions only for
now...). Even more important is that the tlb miss handler is much slower
on a NPT/EPT guest than for a regular shadow paging or no-virtualization
scenario. So maximizing the amount of virtual memory cached by the TLB
pays off significantly more with NPT/EPT than without (even if there would
be no significant speedup in the tlb-miss runtime).The first (and more tedious) part of this work requires allowing the VM to
handle anonymous hugepages mixed with regular pages transparently on
regular anonymous vmas. This is what this patch tries to achieve in the
least intrusive possible way. We want hugepages and hugetlb to be used in
a way so that all applications can benefit without changes (as usual we
leverage the KVM virtualization design: by improving the Linux VM at
large, KVM gets the performance boost too).The most important design choice is: always fallback to 4k allocation if
the hugepage allocation fails! This is the _very_ opposite of some large
pagecache patches that failed with -EIO back then if a 64k (or similar)
allocation failed...Second important decision (to reduce the impact of the feature on the
existing pagetable handling code) is that at any time we can split an
hugepage into 512 regular pages and it has to be done with an operation
that can't fail. This way the reliability of the swapping isn't decreased
(no need to allocate memory when we are short on memory to swap) and it's
trivial to plug a split_huge_page* one-liner where needed without
polluting the VM. Over time we can teach mprotect, mremap and friends to
handle pmd_trans_huge natively without calling split_huge_page*. The fact
it can't fail isn't just for swap: if split_huge_page would return -ENOMEM
(instead of the current void) we'd need to rollback the mprotect from the
middle of it (ideally including undoing the split_vma) which would be a
big change and in the very wrong direction (it'd likely be simpler not to
call split_huge_page at all and to teach mprotect and friends to handle
hugepages instead of rolling them back from the middle). In short the
very value of split_huge_page is that it can't fail.The collapsing and madvise(MADV_HUGEPAGE) part will remain separated and
incremental and it'll just be an "harmless" addition later if this initial
part is agreed upon. It also should be noted that locking-wise replacing
regular pages with hugepages is going to be very easy if compared to what
I'm doing below in split_huge_page, as it will only happen when
page_count(page) matches page_mapcount(page) if we can take the PG_lock
and mmap_sem in write mode. collapse_huge_page will be a "best effort"
that (unlike split_huge_page) can fail at the minimal sign of trouble and
we can try again later. collapse_huge_page will be similar to how KSM
works and the madvise(MADV_HUGEPAGE) will work similar to
madvise(MADV_MERGEABLE).The default I like is that transparent hugepages are used at page fault
time. This can be changed with
/sys/kernel/mm/transparent_hugepage/enabled. The control knob can be set
to three values "always", "madvise", "never" which mean respectively that
hugepages are always used, or only inside madvise(MADV_HUGEPAGE) regions,
or never used. /sys/kernel/mm/transparent_hugepage/defrag instead
controls if the hugepage allocation should defrag memory aggressively
"always", only inside "madvise" regions, or "never".The pmd_trans_splitting/pmd_trans_huge locking is very solid. The
put_page (from get_user_page users that can't use mmu notifier like
O_DIRECT) that runs against a __split_huge_page_refcount instead was a
pain to serialize in a way that would result always in a coherent page
count for both tail and head. I think my locking solution with a
compound_lock taken only after the page_first is valid and is still a
PageHead should be safe but it surely needs review from SMP race point of
view. In short there is no current existing way to serialize the O_DIRECT
final put_page against split_huge_page_refcount so I had to invent a new
one (O_DIRECT loses knowledge on the mapping status by the time gup_fast
returns so...). And I didn't want to impact all gup/gup_fast users for
now, maybe if we change the gup interface substantially we can avoid this
locking, I admit I didn't think too much about it because changing the gup
unpinning interface would be invasive.If we ignored O_DIRECT we could stick to the existing compound refcounting
code, by simply adding a get_user_pages_fast_flags(foll_flags) where KVM
(and any other mmu notifier user) would call it without FOLL_GET (and if
FOLL_GET isn't set we'd just BUG_ON if nobody registered itself in the
current task mmu notifier list yet). But O_DIRECT is fundamental for
decent performance of virtualized I/O on fast storage so we can't avoid it
to solve the race of put_page against split_huge_page_refcount to achieve
a complete hugepage feature for KVM.Swap and oom works fine (well just like with regular pages ;). MMU
notifier is handled transparently too, with the exception of the young bit
on the pmd, that didn't have a range check but I think KVM will be fine
because the whole point of hugepages is that EPT/NPT will also use a huge
pmd when they notice gup returns pages with PageCompound set, so they
won't care of a range and there's just the pmd young bit to check in that
case.NOTE: in some cases if the L2 cache is small, this may slowdown and waste
memory during COWs because 4M of memory are accessed in a single fault
instead of 8k (the payoff is that after COW the program can run faster).
So we might want to switch the copy_huge_page (and clear_huge_page too) to
not temporal stores. I also extensively researched ways to avoid this
cache trashing with a full prefault logic that would cow in 8k/16k/32k/64k
up to 1M (I can send those patches that fully implemented prefault) but I
concluded they're not worth it and they add an huge additional complexity
and they remove all tlb benefits until the full hugepage has been faulted
in, to save a little bit of memory and some cache during app startup, but
they still don't improve substantially the cache-trashing during startup
if the prefault happens in >4k chunks. One reason is that those 4k pte
entries copied are still mapped on a perfectly cache-colored hugepage, so
the trashing is the worst one can generate in those copies (cow of 4k page
copies aren't so well colored so they trashes less, but again this results
in software running faster after the page fault). Those prefault patches
allowed things like a pte where post-cow pages were local 4k regular anon
pages and the not-yet-cowed pte entries were pointing in the middle of
some hugepage mapped read-only. If it doesn't payoff substantially with
todays hardware it will payoff even less in the future with larger l2
caches, and the prefault logic would blot the VM a lot. If one is
emebdded transparent_hugepage can be disabled during boot with sysfs or
with the boot commandline parameter transparent_hugepage=0 (or
transparent_hugepage=2 to restrict hugepages inside madvise regions) that
will ensure not a single hugepage is allocated at boot time. It is simple
enough to just disable transparent hugepage globally and let transparent
hugepages be allocated selectively by applications in the MADV_HUGEPAGE
region (both at page fault time, and if enabled with the
collapse_huge_page too through the kernel daemon).This patch supports only hugepages mapped in the pmd, archs that have
smaller hugepages will not fit in this patch alone. Also some archs like
power have certain tlb limits that prevents mixing different page size in
the same regions so they will not fit in this framework that requires
"graceful fallback" to basic PAGE_SIZE in case of physical memory
fragmentation. hugetlbfs remains a perfect fit for those because its
software limits happen to match the hardware limits. hugetlbfs also
remains a perfect fit for hugepage sizes like 1GByte that cannot be hoped
to be found not fragmented after a certain system uptime and that would be
very expensive to defragment with relocation, so requiring reservation.
hugetlbfs is the "reservation way", the point of transparent hugepages is
not to have any reservation at all and maximizing the use of cache and
hugepages at all times automatically.Some performance result:
vmx andrea # LD_PRELOAD=/usr/lib64/libhugetlbfs.so HUGETLB_MORECORE=yes HUGETLB_PATH=/mnt/huge/ ./largep
ages3
memset page fault 1566023
memset tlb miss 453854
memset second tlb miss 453321
random access tlb miss 41635
random access second tlb miss 41658
vmx andrea # LD_PRELOAD=/usr/lib64/libhugetlbfs.so HUGETLB_MORECORE=yes HUGETLB_PATH=/mnt/huge/ ./largepages3
memset page fault 1566471
memset tlb miss 453375
memset second tlb miss 453320
random access tlb miss 41636
random access second tlb miss 41637
vmx andrea # ./largepages3
memset page fault 1566642
memset tlb miss 453417
memset second tlb miss 453313
random access tlb miss 41630
random access second tlb miss 41647
vmx andrea # ./largepages3
memset page fault 1566872
memset tlb miss 453418
memset second tlb miss 453315
random access tlb miss 41618
random access second tlb miss 41659
vmx andrea # echo 0 > /proc/sys/vm/transparent_hugepage
vmx andrea # ./largepages3
memset page fault 2182476
memset tlb miss 460305
memset second tlb miss 460179
random access tlb miss 44483
random access second tlb miss 44186
vmx andrea # ./largepages3
memset page fault 2182791
memset tlb miss 460742
memset second tlb miss 459962
random access tlb miss 43981
random access second tlb miss 43988============
#include
#include
#include
#include#define SIZE (3UL*1024*1024*1024)
int main()
{
char *p = malloc(SIZE), *p2;
struct timeval before, after;gettimeofday(&before, NULL);
memset(p, 0, SIZE);
gettimeofday(&after, NULL);
printf("memset page fault %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);gettimeofday(&before, NULL);
memset(p, 0, SIZE);
gettimeofday(&after, NULL);
printf("memset tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);gettimeofday(&before, NULL);
memset(p, 0, SIZE);
gettimeofday(&after, NULL);
printf("memset second tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);gettimeofday(&before, NULL);
for (p2 = p; p2 < p+SIZE; p2 += 4096)
*p2 = 0;
gettimeofday(&after, NULL);
printf("random access tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);gettimeofday(&before, NULL);
for (p2 = p; p2 < p+SIZE; p2 += 4096)
*p2 = 0;
gettimeofday(&after, NULL);
printf("random access second tlb miss %Lu\n",
(after.tv_sec-before.tv_sec)*1000000UL +
after.tv_usec-before.tv_usec);return 0;
}
============Signed-off-by: Andrea Arcangeli
Acked-by: Rik van Riel
Signed-off-by: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Paging logic that splits the page before it is unmapped and added to swap
to ensure backwards compatibility with the legacy swap code. Eventually
swap should natively pageout the hugepages to increase performance and
decrease seeking and fragmentation of swap space. swapoff can just skip
over huge pmd as they cannot be part of swap yet. In add_to_swap be
careful to split the page only if we got a valid swap entry so we don't
split hugepages with a full swap.In theory we could split pages before isolating them during the lru scan,
but for khugepaged to be safe, I'm relying on either mmap_sem write mode,
or PG_lock taken, so split_huge_page has to run either with mmap_sem
read/write mode or PG_lock taken. Calling it from isolate_lru_page would
make locking more complicated, in addition to that split_huge_page would
deadlock if called by __isolate_lru_page because it has to take the lru
lock to add the tail pages.Signed-off-by: Andrea Arcangeli
Acked-by: Mel Gorman
Acked-by: Rik van Riel
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Dec, 2010
1 commit
-
clean up comment.
Signed-off-by: Figo.zhang
Acked-by: Rik van Riel
Signed-off-by: Jiri Kosina
27 Oct, 2010
4 commits
-
Make anon_vma_chain_free() static. It is called only in rmap.c and the
corresponding alloc function is already static.Signed-off-by: Namhyung Kim
Cc: Andi Kleen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The page_check_address() conditionally grabs *@ptlp in case of returning
non-NULL. Rename and wrap it using __cond_lock() removes following
warnings from sparse:mm/rmap.c:472:9: warning: context imbalance in 'page_mapped_in_vma' - unexpected unlock
mm/rmap.c:524:9: warning: context imbalance in 'page_referenced_one' - unexpected unlock
mm/rmap.c:706:9: warning: context imbalance in 'page_mkclean_one' - unexpected unlock
mm/rmap.c:1066:9: warning: context imbalance in 'try_to_unmap_one' - unexpected unlockSigned-off-by: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The page_lock_anon_vma() conditionally grabs RCU and anon_vma lock but
page_unlock_anon_vma() releases them unconditionally. This leads sparse
to complain about context imbalance. Annotate them.Signed-off-by: Namhyung Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
* 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6: (22 commits)
Add _addr_lsb field to ia64 siginfo
Fix migration.c compilation on s390
HWPOISON: Remove retry loop for try_to_unmap
HWPOISON: Turn addr_valid from bitfield into char
HWPOISON: Disable DEBUG by default
HWPOISON: Convert pr_debugs to pr_info
HWPOISON: Improve comments in memory-failure.c
x86: HWPOISON: Report correct address granuality for huge hwpoison faults
Encode huge page size for VM_FAULT_HWPOISON errors
Fix build error with !CONFIG_MIGRATION
hugepage: move is_hugepage_on_freelist inside ifdef to avoid warning
Clean up __page_set_anon_rmap
HWPOISON, hugetlb: fix unpoison for hugepage
HWPOISON, hugetlb: soft offlining for hugepage
HWPOSION, hugetlb: recover from free hugepage error when !MF_COUNT_INCREASED
hugetlb: move refcounting in hugepage allocation inside hugetlb_lock
HWPOISON, hugetlb: add free check to dequeue_hwpoison_huge_page()
hugetlb: hugepage migration core
hugetlb: redefine hugepage copy functions
hugetlb: add allocate function for hugepage migration
...
