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Currently the 4th parameter of get_user_pages() is called len, but its
in pages, not bytes. Rename the thing to nr_pages to avoid future
confusion.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/{vfs-2.6,audit-current}
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
another race fix in jfs_check_acl()
Get "no acls for this inode" right, fix shmem breakage
inline functions left without protection of ifdef (acl)
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current:
audit: inode watches depend on CONFIG_AUDIT not CONFIG_AUDIT_SYSCALL
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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SLUB uses higher order allocations by default but falls back to small
orders under memory pressure. Make sure the GFP mask used in the initial
allocation doesn't include __GFP_NOFAIL.
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Traditionally, we never failed small orders (even regardless of any
__GFP_NOFAIL flags), and slab will allocate order-1 allocations even for
small allocations that could fit in a single page (in order to avoid
excessive fragmentation).
Maybe we should remove this warning entirely, but before making that
judgement, at least limit it to bigger allocations.
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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After downing/upping a cpu, an attempt to set
/proc/sys/vm/percpu_pagelist_fraction results in an oops in
percpu_pagelist_fraction_sysctl_handler().
If a processor is downed then we need to set the pageset pointer back to
the boot pageset.
Updates of the high water marks should not access pagesets of unpopulated
zones (those pointer go to the boot pagesets which would be no longer
functional if their size would be increased beyond zero).
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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If a kthread happens to use get_user_pages() on an mm (as KSM does),
there's a chance that it will end up trying to read in a swap page, then
oops in grab_swap_token() because the kthread has no mm: GUP passes down
the right mm, so grab_swap_token() ought to be using it.
We have not identified a stronger case than KSM's daemon (not yet in
mainline), but the issue must have come up before, since RHEL has included
a fix for this for years (though a different fix, they just back out of
grab_swap_token if current->mm is unset: which is what we first proposed,
but using the right mm here seems more correct).
Reported-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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* 'kmemleak' of git://linux-arm.org/linux-2.6:
kmemleak: Do not force the slab debugging Kconfig options
kmemleak: use pr_fmt
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Indeed FOLL_WRITE matches FAULT_FLAG_WRITE, matches GUP_FLAGS_WRITE,
and it's tempting to devise a set of Grand Unified Paging flags;
but not today. So until then, let's rely upon the compiler to spot
the coincidence, "rather than have that subtle dependency and a
comment for it" - as you remarked in another context yesterday.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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handle_mm_fault() is now passing fault flags rather than write_access
down to hugetlb_fault(), so better recognize that in hugetlb_fault(),
and in hugetlb_no_page().
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The isolated page is "cursor_page" not "page".
This could cause LRU list corruption under memory pressure, caught by
CONFIG_DEBUG_LIST.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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This allows the callers to now pass down the full set of FAULT_FLAG_xyz
flags to handle_mm_fault(). All callers have been (mechanically)
converted to the new calling convention, there's almost certainly room
for architectures to clean up their code and then add FAULT_FLAG_RETRY
when that support is added.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The fault handling routines really want more fine-grained flags than a
single "was it a write fault" boolean - the callers will want to set
flags like "you can return a retry error" etc.
And that's actually how the VM works internally, but right now the
top-level fault handling functions in mm/memory.c all pass just the
'write_access' boolean around.
This switches them over to pass around the FAULT_FLAG_xyzzy 'flags'
variable instead. The 'write_access' calling convention still exists
for the exported 'handle_mm_fault()' function, but that is next.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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da456f1 "page allocator: do not disable interrupts in free_page_mlock()" moved
the PG_mlocked clearing after the flag sanity checking which makes mlocked
pages always trigger 'bad page'. Fix this by clearing the bit up front.
Reported--and-debugged-by: Peter Chubb <peter.chubb@nicta.com.au>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Tested-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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[akpm@linux-foundation.org: cleanup]
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The page allocator also needs the masking of gfp flags during boot,
so this moves it out of slab/slub and uses it with the page allocator
as well.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Try to fix memcg's lru rotation sanity: make memcg use the same logic as
the global LRU does.
Now, at __isolate_lru_page() retruns -EBUSY, the page is rotated to the
tail of LRU in global LRU's isolate LRU pages. But in memcg, it's not
handled. This makes memcg do the same behavior as global LRU and rotate
LRU in the page is busy.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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A user can set memcg.limit_in_bytes == memcg.memsw.limit_in_bytes when the
user just want to limit the total size of applications, in other words,
not very interested in memory usage itself. In this case, swap-out will
be done only by global-LRU.
But, under current implementation, memory.limit_in_bytes is checked at
first and try_to_free_page() may do swap-out. But, that swap-out is
useless for memsw.limit_in_bytes and the thread may hit limit again.
This patch tries to fix the current behavior at memory.limit ==
memsw.limit case. And documentation is updated to explain the behavior of
this special case.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This patch fixes mis-accounting of swap usage in memcg.
In the current implementation, memcg's swap account is uncharged only when
swap is completely freed. But there are several cases where swap cannot
be freed cleanly. For handling that, this patch changes that memcg
uncharges swap account when swap has no references other than cache.
By this, memcg's swap entry accounting can be fully synchronous with the
application's behavior.
This patch also changes memcg's hooks for swap-out.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We don't need to check do_swap_account in the case that the function which
checks do_swap_account will never get called if do_swap_account == 0.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add file RSS tracking per memory cgroup
We currently don't track file RSS, the RSS we report is actually anon RSS.
All the file mapped pages, come in through the page cache and get
accounted there. This patch adds support for accounting file RSS pages.
It should
1. Help improve the metrics reported by the memory resource controller
2. Will form the basis for a future shared memory accounting heuristic
that has been proposed by Kamezawa.
Unfortunately, we cannot rename the existing "rss" keyword used in
memory.stat to "anon_rss". We however, add "mapped_file" data and hope to
educate the end user through documentation.
[hugh.dickins@tiscali.co.uk: fix mem_cgroup_update_mapped_file_stat oops]
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.cn>
Cc: Paul Menage <menage@google.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Fix some cgroup messages to read better.
Update MAINTAINERS to include mm/*cgroup* files.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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* 'kmemleak' of git://linux-arm.org/linux-2.6:
kmemleak: Fix some typos in comments
kmemleak: Rename kmemleak_panic to kmemleak_stop
kmemleak: Only use GFP_KERNEL|GFP_ATOMIC for the internal allocations
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Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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This is to avoid the confusion created by the "panic" word.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
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Kmemleak allocates memory for pointer tracking and it tries to avoid
using GFP_ATOMIC if the caller doesn't require it. However other gfp
flags may be passed by the caller which aren't required by kmemleak.
This patch filters the gfp flags so that only GFP_KERNEL | GFP_ATOMIC
are used.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
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Conflicts:
mm/slub.c
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'slub/fixes' into for-linus
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* akpm: (182 commits)
fbdev: bf54x-lq043fb: use kzalloc over kmalloc/memset
fbdev: *bfin*: fix __dev{init,exit} markings
fbdev: *bfin*: drop unnecessary calls to memset
fbdev: bfin-t350mcqb-fb: drop unused local variables
fbdev: blackfin has __raw I/O accessors, so use them in fb.h
fbdev: s1d13xxxfb: add accelerated bitblt functions
tcx: use standard fields for framebuffer physical address and length
fbdev: add support for handoff from firmware to hw framebuffers
intelfb: fix a bug when changing video timing
fbdev: use framebuffer_release() for freeing fb_info structures
radeon: P2G2CLK_ALWAYS_ONb tested twice, should 2nd be P2G2CLK_DAC_ALWAYS_ONb?
s3c-fb: CPUFREQ frequency scaling support
s3c-fb: fix resource releasing on error during probing
carminefb: fix possible access beyond end of carmine_modedb[]
acornfb: remove fb_mmap function
mb862xxfb: use CONFIG_OF instead of CONFIG_PPC_OF
mb862xxfb: restrict compliation of platform driver to PPC
Samsung SoC Framebuffer driver: add Alpha Channel support
atmel-lcdc: fix pixclock upper bound detection
offb: use framebuffer_alloc() to allocate fb_info struct
...
Manually fix up conflicts due to kmemcheck in mm/slab.c
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At lumpy reclaim, a page failed to be taken by __isolate_lru_page() can be
pushed back to "src" list by list_move(). But the page may not be from
"src" list. This pushes the page back to wrong LRU. And list_move()
itself is unnecessary because the page is not on top of LRU. Then, leave
it as it is if __isolate_lru_page() fails.
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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On NUMA machines, the administrator can configure zone_reclaim_mode that
is a more targetted form of direct reclaim. On machines with large NUMA
distances for example, a zone_reclaim_mode defaults to 1 meaning that
clean unmapped pages will be reclaimed if the zone watermarks are not
being met.
There is a heuristic that determines if the scan is worthwhile but it is
possible that the heuristic will fail and the CPU gets tied up scanning
uselessly. Detecting the situation requires some guesswork and
experimentation so this patch adds a counter "zreclaim_failed" to
/proc/vmstat. If during high CPU utilisation this counter is increasing
rapidly, then the resolution to the problem may be to set
/proc/sys/vm/zone_reclaim_mode to 0.
[akpm@linux-foundation.org: name things consistently]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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On NUMA machines, the administrator can configure zone_reclaim_mode that
is a more targetted form of direct reclaim. On machines with large NUMA
distances for example, a zone_reclaim_mode defaults to 1 meaning that
clean unmapped pages will be reclaimed if the zone watermarks are not
being met. The problem is that zone_reclaim() failing at all means the
zone gets marked full.
This can cause situations where a zone is usable, but is being skipped
because it has been considered full. Take a situation where a large tmpfs
mount is occuping a large percentage of memory overall. The pages do not
get cleaned or reclaimed by zone_reclaim(), but the zone gets marked full
and the zonelist cache considers them not worth trying in the future.
This patch makes zone_reclaim() return more fine-grained information about
what occured when zone_reclaim() failued. The zone only gets marked full
if it really is unreclaimable. If it's a case that the scan did not occur
or if enough pages were not reclaimed with the limited reclaim_mode, then
the zone is simply skipped.
There is a side-effect to this patch. Currently, if zone_reclaim()
successfully reclaimed SWAP_CLUSTER_MAX, an allocation attempt would go
ahead. With this patch applied, zone watermarks are rechecked after
zone_reclaim() does some work.
This bug was introduced by commit 9276b1bc96a132f4068fdee00983c532f43d3a26
("memory page_alloc zonelist caching speedup") way back in 2.6.19 when the
zonelist_cache was introduced. It was not intended that zone_reclaim()
aggressively consider the zone to be full when it failed as full direct
reclaim can still be an option. Due to the age of the bug, it should be
considered a -stable candidate.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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can reclaim
A bug was brought to my attention against a distro kernel but it affects
mainline and I believe problems like this have been reported in various
guises on the mailing lists although I don't have specific examples at the
moment.
The reported problem was that malloc() stalled for a long time (minutes in
some cases) if a large tmpfs mount was occupying a large percentage of
memory overall. The pages did not get cleaned or reclaimed by
zone_reclaim() because the zone_reclaim_mode was unsuitable, but the lists
are uselessly scanned frequencly making the CPU spin at near 100%.
This patchset intends to address that bug and bring the behaviour of
zone_reclaim() more in line with expectations which were noticed during
investigation. It is based on top of mmotm and takes advantage of
Kosaki's work with respect to zone_reclaim().
Patch 1 fixes the heuristics that zone_reclaim() uses to determine if the
scan should go ahead. The broken heuristic is what was causing the
malloc() stall as it uselessly scanned the LRU constantly. Currently,
zone_reclaim is assuming zone_reclaim_mode is 1 and historically it
could not deal with tmpfs pages at all. This fixes up the heuristic so
that an unnecessary scan is more likely to be correctly avoided.
Patch 2 notes that zone_reclaim() returning a failure automatically means
the zone is marked full. This is not always true. It could have
failed because the GFP mask or zone_reclaim_mode were unsuitable.
Patch 3 introduces a counter zreclaim_failed that will increment each
time the zone_reclaim scan-avoidance heuristics fail. If that
counter is rapidly increasing, then zone_reclaim_mode should be
set to 0 as a temporarily resolution and a bug reported because
the scan-avoidance heuristic is still broken.
This patch:
On NUMA machines, the administrator can configure zone_reclaim_mode that
is a more targetted form of direct reclaim. On machines with large NUMA
distances for example, a zone_reclaim_mode defaults to 1 meaning that
clean unmapped pages will be reclaimed if the zone watermarks are not
being met.
There is a heuristic that determines if the scan is worthwhile but the
problem is that the heuristic is not being properly applied and is
basically assuming zone_reclaim_mode is 1 if it is enabled. The lack of
proper detection can manfiest as high CPU usage as the LRU list is scanned
uselessly.
Historically, once enabled it was depending on NR_FILE_PAGES which may
include swapcache pages that the reclaim_mode cannot deal with. Patch
vmscan-change-the-number-of-the-unmapped-files-in-zone-reclaim.patch by
Kosaki Motohiro noted that zone_page_state(zone, NR_FILE_PAGES) included
pages that were not file-backed such as swapcache and made a calculation
based on the inactive, active and mapped files. This is far superior when
zone_reclaim==1 but if RECLAIM_SWAP is set, then NR_FILE_PAGES is a
reasonable starting figure.
This patch alters how zone_reclaim() works out how many pages it might be
able to reclaim given the current reclaim_mode. If RECLAIM_SWAP is set in
the reclaim_mode it will either consider NR_FILE_PAGES as potential
candidates or else use NR_{IN}ACTIVE}_PAGES-NR_FILE_MAPPED to discount
swapcache and other non-file-backed pages. If RECLAIM_WRITE is not set,
then NR_FILE_DIRTY number of pages are not candidates. If RECLAIM_SWAP is
not set, then NR_FILE_MAPPED are not.
[kosaki.motohiro@jp.fujitsu.com: Estimate unmapped pages minus tmpfs pages]
[fengguang.wu@intel.com: Fix underflow problem in Kosaki's estimate]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When a task is chosen for oom kill and is found to be PF_EXITING,
__oom_kill_task() is called to elevate the task's timeslice and give it
access to memory reserves so that it may quickly exit.
This privilege is unnecessary, however, if the task has already detached
its mm. Although its possible for the mm to become detached later since
task_lock() is not held, __oom_kill_task() will simply be a no-op in such
circumstances.
Subsequently, it is no longer necessary to warn about killing mm-less
tasks since it is a no-op.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit 2e2e425989080cc534fc0fca154cae515f971cf5 ("vmscan,memcg:
reintroduce sc->may_swap) add may_swap flag and handle it at
get_scan_ratio().
But the result of get_scan_ratio() is ignored when priority == 0, so anon
lru is scanned even if may_swap == 0 or nr_swap_pages == 0. IMHO, this is
not an expected behavior.
As for memcg especially, because of this behavior many and many pages are
swapped-out just in vain when oom is invoked by mem+swap limit.
This patch is for handling may_swap flag more strictly.
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The "move pages to active list" and "move pages to inactive list" code
blocks are mostly identical and can be served by a function.
Thanks to Andrew Morton for pointing this out.
Note that buffer_heads_over_limit check will also be carried out for
re-activated pages, which is slightly different from pre-2.6.28 kernels.
Also, Rik's "vmscan: evict use-once pages first" patch could totally stop
scans of active file list when memory pressure is low. So the net effect
could be, the number of buffer heads is now more likely to grow large.
However that's fine according to Johannes' comments:
I don't think that this could be harmful. We just preserve the buffer
mappings of what we consider the working set and with low memory
pressure, as you say, this set is not big.
As to stripping of reactivated pages: the only pages we re-activate
for now are those VM_EXEC mapped ones. Since we don't expect IO from
or to these pages, removing the buffer mappings in case they grow too
large should be okay, I guess.
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Protect referenced PROT_EXEC mapped pages from being deactivated.
PROT_EXEC(or its internal presentation VM_EXEC) pages normally belong to some
currently running executables and their linked libraries, they shall really be
cached aggressively to provide good user experiences.
Thanks to Johannes Weiner for the advice to reuse the VMA walk in
page_referenced() to get the PROT_EXEC bit.
[more details]
( The consequences of this patch will have to be discussed together with
Rik van Riel's recent patch "vmscan: evict use-once pages first". )
( Some of the good points and insights are taken into this changelog.
Thanks to all the involved people for the great LKML discussions. )
the problem
===========
For a typical desktop, the most precious working set is composed of
*actively accessed*
(1) memory mapped executables
(2) and their anonymous pages
(3) and other files
(4) and the dcache/icache/.. slabs
while the least important data are
(5) infrequently used or use-once files
For a typical desktop, one major problem is busty and large amount of (5)
use-once files flushing out the working set.
Inside the working set, (4) dcache/icache have already been too sticky ;-)
So we only have to care (2) anonymous and (1)(3) file pages.
anonymous pages
===============
Anonymous pages are effectively immune to the streaming IO attack, because we
now have separate file/anon LRU lists. When the use-once files crowd into the
file LRU, the list's "quality" is significantly lowered. Therefore the scan
balance policy in get_scan_ratio() will choose to scan the (low quality) file
LRU much more frequently than the anon LRU.
file pages
==========
Rik proposed to *not* scan the active file LRU when the inactive list grows
larger than active list. This guarantees that when there are use-once streaming
IO, and the working set is not too large(so that active_size < inactive_size),
the active file LRU will *not* be scanned at all. So the not-too-large working
set can be well protected.
But there are also situations where the file working set is a bit large so that
(active_size >= inactive_size), or the streaming IOs are not purely use-once.
In these cases, the active list will be scanned slowly. Because the current
shrink_active_list() policy is to deactivate active pages regardless of their
referenced bits. The deactivated pages become susceptible to the streaming IO
attack: the inactive list could be scanned fast (500MB / 50MBps = 10s) so that
the deactivated pages don't have enough time to get re-referenced. Because a
user tend to switch between windows in intervals from seconds to minutes.
This patch holds mapped executable pages in the active list as long as they
are referenced during each full scan of the active list. Because the active
list is normally scanned much slower, they get longer grace time (eg. 100s)
for further references, which better matches the pace of user operations.
Therefore this patch greatly prolongs the in-cache time of executable code,
when there are moderate memory pressures.
before patch: guaranteed to be cached if reference intervals < I
after patch: guaranteed to be cached if reference intervals < I+A
(except when randomly reclaimed by the lumpy reclaim)
where
A = time to fully scan the active file LRU
I = time to fully scan the inactive file LRU
Note that normally A >> I.
side effects
============
This patch is safe in general, it restores the pre-2.6.28 mmap() behavior
but in a much smaller and well targeted scope.
One may worry about some one to abuse the PROT_EXEC heuristic. But as
Andrew Morton stated, there are other tricks to getting that sort of boost.
Another concern is the PROT_EXEC mapped pages growing large in rare cases,
and therefore hurting reclaim efficiency. But a sane application targeted for
large audience will never use PROT_EXEC for data mappings. If some home made
application tries to abuse that bit, it shall be aware of the consequences.
If it is abused to scale of 2/3 total memory, it gains nothing but overheads.
benchmarks
==========
1) memory tight desktop
1.1) brief summary
- clock time and major faults are reduced by 50%;
- pswpin numbers are reduced to ~1/3.
That means X desktop responsiveness is doubled under high memory/swap pressure.
1.2) test scenario
- nfsroot gnome desktop with 512M physical memory
- run some programs, and switch between the existing windows
after starting each new program.
1.3) progress timing (seconds)
before after programs
0.02 0.02 N xeyes
0.75 0.76 N firefox
2.02 1.88 N nautilus
3.36 3.17 N nautilus --browser
5.26 4.89 N gthumb
7.12 6.47 N gedit
9.22 8.16 N xpdf /usr/share/doc/shared-mime-info/shared-mime-info-spec.pdf
13.58 12.55 N xterm
15.87 14.57 N mlterm
18.63 17.06 N gnome-terminal
21.16 18.90 N urxvt
26.24 23.48 N gnome-system-monitor
28.72 26.52 N gnome-help
32.15 29.65 N gnome-dictionary
39.66 36.12 N /usr/games/sol
43.16 39.27 N /usr/games/gnometris
48.65 42.56 N /usr/games/gnect
53.31 47.03 N /usr/games/gtali
58.60 52.05 N /usr/games/iagno
65.77 55.42 N /usr/games/gnotravex
70.76 61.47 N /usr/games/mahjongg
76.15 67.11 N /usr/games/gnome-sudoku
86.32 75.15 N /usr/games/glines
92.21 79.70 N /usr/games/glchess
103.79 88.48 N /usr/games/gnomine
113.84 96.51 N /usr/games/gnotski
124.40 102.19 N /usr/games/gnibbles
137.41 114.93 N /usr/games/gnobots2
155.53 125.02 N /usr/games/blackjack
179.85 135.11 N /usr/games/same-gnome
224.49 154.50 N /usr/bin/gnome-window-properties
248.44 162.09 N /usr/bin/gnome-default-applications-properties
282.62 173.29 N /usr/bin/gnome-at-properties
323.72 188.21 N /usr/bin/gnome-typing-monitor
363.99 199.93 N /usr/bin/gnome-at-visual
394.21 206.95 N /usr/bin/gnome-sound-properties
435.14 224.49 N /usr/bin/gnome-at-mobility
463.05 234.11 N /usr/bin/gnome-keybinding-properties
503.75 248.59 N /usr/bin/gnome-about-me
554.00 276.27 N /usr/bin/gnome-display-properties
615.48 304.39 N /usr/bin/gnome-network-preferences
693.03 342.01 N /usr/bin/gnome-mouse-properties
759.90 388.58 N /usr/bin/gnome-appearance-properties
937.90 508.47 N /usr/bin/gnome-control-center
1109.75 587.57 N /usr/bin/gnome-keyboard-properties
1399.05 758.16 N : oocalc
1524.64 830.03 N : oodraw
1684.31 900.03 N : ooimpress
1874.04 993.91 N : oomath
2115.12 1081.89 N : ooweb
2369.02 1161.99 N : oowriter
Note that the last ": oo*" commands are actually commented out.
1.4) vmstat numbers (some relevant ones are marked with *)
before after
nr_free_pages 1293 3898
nr_inactive_anon 59956 53460
nr_active_anon 26815 30026
nr_inactive_file 2657 3218
nr_active_file 2019 2806
nr_unevictable 4 4
nr_mlock 4 4
nr_anon_pages 26706 27859
*nr_mapped 3542 4469
nr_file_pages 72232 67681
nr_dirty 1 0
nr_writeback 123 19
nr_slab_reclaimable 3375 3534
nr_slab_unreclaimable 11405 10665
nr_page_table_pages 8106 7864
nr_unstable 0 0
nr_bounce 0 0
*nr_vmscan_write 394776 230839
nr_writeback_temp 0 0
numa_hit 6843353 3318676
numa_miss 0 0
numa_foreign 0 0
numa_interleave 1719 1719
numa_local 6843353 3318676
numa_other 0 0
*pgpgin 5954683 2057175
*pgpgout 1578276 922744
*pswpin 1486615 512238
*pswpout 394568 230685
pgalloc_dma 277432 56602
pgalloc_dma32 6769477 3310348
pgalloc_normal 0 0
pgalloc_movable 0 0
pgfree 7048396 3371118
pgactivate 2036343 1471492
pgdeactivate 2189691 1612829
pgfault 3702176 3100702
*pgmajfault 452116 201343
pgrefill_dma 12185 7127
pgrefill_dma32 334384 653703
pgrefill_normal 0 0
pgrefill_movable 0 0
pgsteal_dma 74214 22179
pgsteal_dma32 3334164 1638029
pgsteal_normal 0 0
pgsteal_movable 0 0
pgscan_kswapd_dma 1081421 1216199
pgscan_kswapd_dma32 58979118 46002810
pgscan_kswapd_normal 0 0
pgscan_kswapd_movable 0 0
pgscan_direct_dma 2015438 1086109
pgscan_direct_dma32 55787823 36101597
pgscan_direct_normal 0 0
pgscan_direct_movable 0 0
pginodesteal 3461 7281
slabs_scanned 564864 527616
kswapd_steal 2889797 1448082
kswapd_inodesteal 14827 14835
pageoutrun 43459 21562
allocstall 9653 4032
pgrotated 384216 228631
1.5) free numbers at the end of the tests
before patch:
total used free shared buffers cached
Mem: 474 467 7 0 0 236
-/+ buffers/cache: 230 243
Swap: 1023 418 605
after patch:
total used free shared buffers cached
Mem: 474 457 16 0 0 236
-/+ buffers/cache: 221 253
Swap: 1023 404 619
2) memory flushing in a file server
2.1) brief summary
The number of major faults from 50 to 3 during 10% cache hot reads.
That means this patch successfully stops major faults when the active file
list is slowly scanned when there are partially cache hot streaming IO.
2.2) test scenario
Do 100000 pread(size=110 pages, offset=(i*100) pages), where 10% of the
pages will be activated:
for i in `seq 0 100 10000000`; do echo $i 110; done > pattern-hot-10
iotrace.rb --load pattern-hot-10 --play /b/sparse
vmmon nr_mapped nr_active_file nr_inactive_file pgmajfault pgdeactivate pgfree
and monitor /proc/vmstat during the time. The test box has 2G memory.
I carried out tests on fresh booted console as well as X desktop, and
fetched the vmstat numbers on
(1) begin: shortly after the big read IO starts;
(2) end: just before the big read IO stops;
(3) restore: the big read IO stops and the zsh working set restored
(4) restore X: after IO, switch back and forth between the urxvt and firefox
windows to restore their working set.
2.3) console mode results
nr_mapped nr_active_file nr_inactive_file pgmajfault pgdeactivate pgfree
2.6.29 VM_EXEC protection ON:
begin: 2481 2237 8694 630 0 574299
end: 275 231976 233914 633 776271 20933042
restore: 370 232154 234524 691 777183 20958453
2.6.29 VM_EXEC protection ON (second run):
begin: 2434 2237 8493 629 0 574195
end: 284 231970 233536 632 771918 20896129
restore: 399 232218 234789 690 774526 20957909
2.6.30-rc4-mm VM_EXEC protection OFF:
begin: 2479 2344 9659 210 0 579643
end: 284 232010 234142 260 772776 20917184
restore: 379 232159 234371 301 774888 20967849
The above console numbers show that
- The startup pgmajfault of 2.6.30-rc4-mm is merely 1/3 that of 2.6.29.
I'd attribute that improvement to the mmap readahead improvements :-)
- The pgmajfault increment during the file copy is 633-630=3 vs 260-210=50.
That's a huge improvement - which means with the VM_EXEC protection logic,
active mmap pages is pretty safe even under partially cache hot streaming IO.
- when active:inactive file lru size reaches 1:1, their scan rates is 1:20.8
under 10% cache hot IO. (computed with formula Dpgdeactivate:Dpgfree)
That roughly means the active mmap pages get 20.8 more chances to get
re-referenced to stay in memory.
- The absolute nr_mapped drops considerably to 1/9 during the big IO, and the
dropped pages are mostly inactive ones. The patch has almost no impact in
this aspect, that means it won't unnecessarily increase memory pressure.
(In contrast, your 20% mmap protection ratio will keep them all, and
therefore eliminate the extra 41 major faults to restore working set
of zsh etc.)
The iotrace.rb read throughput is
151.194384MB/s 284.198252s 100001x 450560b --load pattern-hot-10 --play /b/sparse
which means the inactive list is rotated at the speed of 250MB/s,
so a full scan of which takes about 3.5 seconds, while a full scan
of active file list takes about 77 seconds.
2.4) X mode results
We can reach roughly the same conclusions for X desktop:
nr_mapped nr_active_file nr_inactive_file pgmajfault pgdeactivate pgfree
2.6.30-rc4-mm VM_EXEC protection ON:
begin: 9740 8920 64075 561 0 678360
end: 768 218254 220029 565 798953 21057006
restore: 857 218543 220987 606 799462 21075710
restore X: 2414 218560 225344 797 799462 21080795
2.6.30-rc4-mm VM_EXEC protection OFF:
begin: 9368 5035 26389 554 0 633391
end: 770 218449 221230 661 646472 17832500
restore: 1113 218466 220978 710 649881 17905235
restore X: 2687 218650 225484 947 802700 21083584
- the absolute nr_mapped drops considerably (to 1/13 of the original size)
during the streaming IO.
- the delta of pgmajfault is 3 vs 107 during IO, or 236 vs 393
during the whole process.
Cc: Elladan <elladan@eskimo.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Collect vma->vm_flags of the VMAs that actually referenced the page.
This is preparing for more informed reclaim heuristics, eg. to protect
executable file pages more aggressively. For now only the VM_EXEC bit
will be used by the caller.
Thanks to Johannes, Peter and Minchan for all the good tips.
Acked-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
As function shmem_file_setup does not modify/allocate/free/pass given
filename - mark it as const.
Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The file argument resulted from address_space's readpage long time ago.
We don't use it any more. Let's remove unnecessary argement.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Hugh removed add_to_swap's gfp_mask argument. (mm: remove gfp_mask from
add_to_swap) So we have to remove annotation of gfp_mask of the function.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
SRAT tables may contains nodes of very small size. The arch code may
decide to not activate such a node. However, currently the early boot
code sets N_HIGH_MEMORY for such nodes. These nodes therefore seem to be
active although these nodes have no present pages.
For 64bit N_HIGH_MEMORY == N_NORMAL_MEMORY, so that works for 64 bit too
Signed-off-by: Yinghai Lu <Yinghai@kernel.org>
Tested-by: Jack Steiner <steiner@sgi.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Remove __invalidate_mapping_pages atomic variant now that its sole caller
can sleep (fixed in eccb95cee4f0d56faa46ef22fb94dd4a3578d3eb ("vfs: fix
lock inversion in drop_pagecache_sb()")).
This fixes softlockups that can occur while in the drop_caches path.
Signed-off-by: Mike Waychison <mikew@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The oom killer must be invoked regardless of the order if the allocation
is __GFP_NOFAIL, otherwise it will loop forever when reclaim fails to free
some memory.
Cc: Nick Piggin <npiggin@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This moves the check for OOM_DISABLE to the badness heuristic so it is
only necessary to hold task_lock() once. If the mm is OOM_DISABLE, the
score is 0, which is also correctly exported via /proc/pid/oom_score.
This requires that tasks with badness scores of 0 are prohibited from
being oom killed, which makes sense since they would not allow for future
memory freeing anyway.
Since the oom_adj value is a characteristic of an mm and not a task, it is
no longer necessary to check the oom_adj value for threads sharing the
same memory (except when simply issuing SIGKILLs for threads in other
thread groups).
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The per-task oom_adj value is a characteristic of its mm more than the
task itself since it's not possible to oom kill any thread that shares the
mm. If a task were to be killed while attached to an mm that could not be
freed because another thread were set to OOM_DISABLE, it would have
needlessly been terminated since there is no potential for future memory
freeing.
This patch moves oomkilladj (now more appropriately named oom_adj) from
struct task_struct to struct mm_struct. This requires task_lock() on a
task to check its oom_adj value to protect against exec, but it's already
necessary to take the lock when dereferencing the mm to find the total VM
size for the badness heuristic.
This fixes a livelock if the oom killer chooses a task and another thread
sharing the same memory has an oom_adj value of OOM_DISABLE. This occurs
because oom_kill_task() repeatedly returns 1 and refuses to kill the
chosen task while select_bad_process() will repeatedly choose the same
task during the next retry.
Taking task_lock() in select_bad_process() to check for OOM_DISABLE and in
oom_kill_task() to check for threads sharing the same memory will be
removed in the next patch in this series where it will no longer be
necessary.
Writing to /proc/pid/oom_adj for a kthread will now return -EINVAL since
these threads are immune from oom killing already. They simply report an
oom_adj value of OOM_DISABLE.
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Presently we can know a swap entry is just used as SwapCache via swap_map,
without looking up swap cache.
Then, we have a chance to reuse swap-cache-only swap entries in
get_swap_pages().
This patch tries to free swap-cache-only swap entries if swap is not
enough.
Note: We hit following path when swap_cluster code cannot find a free
cluster. Then, vm_swap_full() is not only condition to allow the kernel
to reclaim unused swap.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This is a part of the patches for fixing memcg's swap accountinf leak.
But, IMHO, not a bad patch even if no memcg.
There are 2 kinds of references to swap.
- reference from swap entry
- reference from swap cache
Then,
- If there is swap cache && swap's refcnt is 1, there is only swap cache.
(*) swapcount(entry) == 1 && find_get_page(swapper_space, entry) != NULL
This counting logic have worked well for a long time. But considering
that we cannot know there is a _real_ reference or not by swap_map[],
current usage of counter is not very good.
This patch adds a flag SWAP_HAS_CACHE and recored information that a swap
entry has a cache or not. This will remove -1 magic used in swapfile.c
and be a help to avoid unnecessary find_get_page().
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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