I'm running a shmem pagefault test case (see attached file) under a 64 CPU
system. Profile shows shmem_inode_info->lock is heavily contented and
100% CPUs time are trying to get the lock. In the pagefault (no swap)
case, shmem_getpage gets the lock twice, the last one is avoidable if we
prealloc a page so we could reduce one time of locking. This is what
below patch does.
The result of the test case:
2.6.35-rc3: ~20s
2.6.35-rc3 + patch: ~12s
so this is 40% improvement.
One might argue if we could have better locking for shmem. But even shmem
is lockless, the pagefault will soon have pagecache lock heavily contented
because shmem must add new page to pagecache. So before we have better
locking for pagecache, improving shmem locking doesn't have too much
improvement. I did a similar pagefault test against a ramfs file, the
test result is ~10.5s.
[akpm@linux-foundation.org: fix comment, clean up code layout, elimintate code duplication]
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Zhang, Yanmin" <yanmin.zhang@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current implementation of tmpfs is not scalable. We found that
stat_lock is contended by multiple threads when we need to get a new page,
leading to useless spinning inside this spin lock.
This patch makes use of the percpu_counter library to maintain local count
of used blocks to speed up getting and returning of pages. So the
acquisition of stat_lock is unnecessary for getting and returning blocks,
improving the performance of tmpfs on system with large number of cpus.
On a 4 socket 32 core NHM-EX system, we saw improvement of 270%.
The implementation below has a slight chance of race between threads
causing a slight overshoot of the maximum configured blocks. However, any
overshoot is small, and is bounded by the number of cpus. This happens
when the number of used blocks is slightly below the maximum configured
blocks when a thread checks the used block count, and another thread
allocates the last block before the current thread does. This should not
be a problem for tmpfs, as the overshoot is most likely to be a few blocks
and bounded. If a strict limit is really desired, then configured the max
blocks to be the limit less the number of cpus in system.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
No real bugs, just some dead code and some fixups.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
migrate_pages() is using >500 bytes stack. Reduce it.
mm/mempolicy.c: In function 'sys_migrate_pages':
mm/mempolicy.c:1344: warning: the frame size of 528 bytes is larger than 512 bytes
[akpm@linux-foundation.org: don't play with a might-be-NULL pointer]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The sum_vm_events passes cpumask for for_each_cpu(). But it's useless
since we have for_each_online_cpu. Althougth it's tirival overhead, it's
not good about coding consistency.
Let's use for_each_online_cpu instead of for_each_cpu with cpumask
argument.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
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>
__out_of_memory() only has a single caller, so fold it into
out_of_memory() and add a comment about locking for its call to
oom_kill_process().
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-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>
select_bad_process() and __out_of_memory() doe not need their enum
oom_constraint arguments: it's possible to pass a NULL nodemask if
constraint == CONSTRAINT_MEMORY_POLICY in the caller, out_of_memory().
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-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>
We have been used naming try_set_zone_oom and clear_zonelist_oom.
The role of functions is to lock of zonelist for preventing parallel
OOM. So clear_zonelist_oom makes sense but try_set_zone_oome is rather
awkward and unmatched with clear_zonelist_oom.
Let's change it with try_set_zonelist_oom.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: 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>
Remove the redundancy in __oom_kill_task() since:
- init can never be passed to this function: it will never be PF_EXITING
or selectable from select_bad_process(), and
- it will never be passed a task from oom_kill_task() without an ->mm
and we're unconcerned about detachment from exiting tasks, there's no
reason to protect them against SIGKILL or access to memory reserves.
Also moves the kernel log message to a higher level since the verbosity is
not always emitted here; we need not print an error message if an exiting
task is given a longer timeslice.
__oom_kill_task() only has a single caller, so it can be merged into that
function at the same time.
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: 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>
It is possible to remove the special pagefault oom handler by simply oom
locking all system zones and then calling directly into out_of_memory().
All populated zones must have ZONE_OOM_LOCKED set, otherwise there is a
parallel oom killing in progress that will lead to eventual memory freeing
so it's not necessary to needlessly kill another task. The context in
which the pagefault is allocating memory is unknown to the oom killer, so
this is done on a system-wide level.
If a task has already been oom killed and hasn't fully exited yet, this
will be a no-op since select_bad_process() recognizes tasks across the
system with TIF_MEMDIE set.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: 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>
There are various points in the oom killer where the kernel must determine
whether to panic or not. It's better to extract this to a helper function
to remove all the confusion as to its semantics.
Also fix a call to dump_header() where tasklist_lock is not read- locked,
as required.
There's no functional change with this patch.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: 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>
If memory has been depleted in lowmem zones even with the protection
afforded to it by /proc/sys/vm/lowmem_reserve_ratio, it is unlikely that
killing current users will help. The memory is either reclaimable (or
migratable) already, in which case we should not invoke the oom killer at
all, or it is pinned by an application for I/O. Killing such an
application may leave the hardware in an unspecified state and there is no
guarantee that it will be able to make a timely exit.
Lowmem allocations are now failed in oom conditions when __GFP_NOFAIL is
not used so that the task can perhaps recover or try again later.
Previously, the heuristic provided some protection for those tasks with
CAP_SYS_RAWIO, but this is no longer necessary since we will not be
killing tasks for the purposes of ISA allocations.
high_zoneidx is gfp_zone(gfp_flags), meaning that ZONE_NORMAL will be the
default for all allocations that are not __GFP_DMA, __GFP_DMA32,
__GFP_HIGHMEM, and __GFP_MOVABLE on kernels configured to support those
flags. Testing for high_zoneidx being less than ZONE_NORMAL will only
return true for allocations that have either __GFP_DMA or __GFP_DMA32.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: 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>
The oom killer tasklist dump, enabled with the oom_dump_tasks sysctl, is
very helpful information in diagnosing why a user's task has been killed.
It emits useful information such as each eligible thread's memory usage
that can determine why the system is oom, so it should be enabled by
default.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: 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>
The oom killer presently kills current whenever there is no more memory
free or reclaimable on its mempolicy's nodes. There is no guarantee that
current is a memory-hogging task or that killing it will free any
substantial amount of memory, however.
In such situations, it is better to scan the tasklist for nodes that are
allowed to allocate on current's set of nodes and kill the task with the
highest badness() score. This ensures that the most memory-hogging task,
or the one configured by the user with /proc/pid/oom_adj, is always
selected in such scenarios.
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: 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>
When a task is chosen for oom kill, the oom killer first attempts to
sacrifice a child not sharing its parent's memory instead. Unfortunately,
this often kills in a seemingly random fashion based on the ordering of
the selected task's child list. Additionally, it is not guaranteed at all
to free a large amount of memory that we need to prevent additional oom
killing in the very near future.
Instead, we now only attempt to sacrifice the worst child not sharing its
parent's memory, if one exists. The worst child is indicated with the
highest badness() score. This serves two advantages: we kill a
memory-hogging task more often, and we allow the configurable
/proc/pid/oom_adj value to be considered as a factor in which child to
kill.
Reviewers may observe that the previous implementation would iterate
through the children and attempt to kill each until one was successful and
then the parent if none were found while the new code simply kills the
most memory-hogging task or the parent. Note that the only time
oom_kill_task() fails, however, is when a child does not have an mm or has
a /proc/pid/oom_adj of OOM_DISABLE. badness() returns 0 for both cases,
so the final oom_kill_task() will always succeed.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-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>
Tasks that do not share the same set of allowed nodes with the task that
triggered the oom should not be considered as candidates for oom kill.
Tasks in other cpusets with a disjoint set of mems would be unfairly
penalized otherwise because of oom conditions elsewhere; an extreme
example could unfairly kill all other applications on the system if a
single task in a user's cpuset sets itself to OOM_DISABLE and then uses
more memory than allowed.
Killing tasks outside of current's cpuset rarely would free memory for
current anyway. To use a sane heuristic, we must ensure that killing a
task would likely free memory for current and avoid needlessly killing
others at all costs just because their potential memory freeing is
unknown. It is better to kill current than another task needlessly.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-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>
It's unnecessary to SIGKILL a task that is already PF_EXITING and can
actually cause a NULL pointer dereference of the sighand if it has already
been detached. Instead, simply set TIF_MEMDIE so it has access to memory
reserves and can quickly exit as the comment implies.
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: 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>
It's possible to livelock the page allocator if a thread has mm->mmap_sem
and fails to make forward progress because the oom killer selects another
thread sharing the same ->mm to kill that cannot exit until the semaphore
is dropped.
The oom killer will not kill multiple tasks at the same time; each oom
killed task must exit before another task may be killed. Thus, if one
thread is holding mm->mmap_sem and cannot allocate memory, all threads
sharing the same ->mm are blocked from exiting as well. In the oom kill
case, that means the thread holding mm->mmap_sem will never free
additional memory since it cannot get access to memory reserves and the
thread that depends on it with access to memory reserves cannot exit
because it cannot acquire the semaphore. Thus, the page allocators
livelocks.
When the oom killer is called and current happens to have a pending
SIGKILL, this patch automatically gives it access to memory reserves and
returns. Upon returning to the page allocator, its allocation will
hopefully succeed so it can quickly exit and free its memory. If not, the
page allocator will fail the allocation if it is not __GFP_NOFAIL.
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: 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>
When find_lock_task_mm() returns a thread other than p in dump_tasks(),
its name should be displayed instead. This is the thread that will be
targeted by the oom killer, not its mm-less parent.
This also allows us to safely dereference task->comm without needing
get_task_comm().
While we're here, remove the cast on task_cpu(task) as Andrew suggested.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The comments in dump_tasks() should be updated to be more clear about why
tasks are filtered and how they are filtered by its argument.
An unnecessary comment concerning a check for is_global_init() is removed
since it isn't of importance.
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
dump_task() should use find_lock_task_mm() too. It is necessary for
protecting task-exiting race.
dump_tasks() currently filters any task that does not have an attached
->mm since it incorrectly assumes that it must either be in the process of
exiting and has detached its memory or that it's a kernel thread;
multithreaded tasks may actually have subthreads that have a valid ->mm
pointer and thus those threads should actually be displayed. This change
finds those threads, if they exist, and emit their information along with
the rest of the candidate tasks for kill.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Almost all ->mm == NULL checks in oom_kill.c are wrong.
The current code assumes that the task without ->mm has already released
its memory and ignores the process. However this is not necessarily true
when this process is multithreaded, other live sub-threads can use this
->mm.
- Remove the "if (!p->mm)" check in select_bad_process(), it is
just wrong.
- Add the new helper, find_lock_task_mm(), which finds the live
thread which uses the memory and takes task_lock() to pin ->mm
- change oom_badness() to use this helper instead of just checking
->mm != NULL.
- As David pointed out, select_bad_process() must never choose the
task without ->mm, but no matter what oom_badness() returns the
task can be chosen if nothing else has been found yet.
Change oom_badness() to return int, change it to return -1 if
find_lock_task_mm() fails, and change select_bad_process() to
check points >= 0.
Note! This patch is not enough, we need more changes.
- oom_badness() was fixed, but oom_kill_task() still ignores
the task without ->mm
- oom_forkbomb_penalty() should use find_lock_task_mm() too,
and it also needs other changes to actually find the first
first-descendant children
This will be addressed later.
[kosaki.motohiro@jp.fujitsu.com: use in badness(), __oom_kill_task()]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-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>
select_bad_process() checks PF_EXITING to detect the task which is going
to release its memory, but the logic is very wrong.
- a single process P with the dead group leader disables
select_bad_process() completely, it will always return
ERR_PTR() while P can live forever
- if the PF_EXITING task has already released its ->mm
it doesn't make sense to expect it is goiing to free
more memory (except task_struct/etc)
Change the code to ignore the PF_EXITING tasks without ->mm.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-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>
select_bad_process() thinks a kernel thread can't have ->mm != NULL, this
is not true due to use_mm().
Change the code to check PF_KTHREAD.
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
KSM reference counts can cause an anon_vma to exist after the processe it
belongs to have already exited. Because the anon_vma lock now lives in
the root anon_vma, we need to ensure that the root anon_vma stays around
until after all the "child" anon_vmas have been freed.
The obvious way to do this is to have a "child" anon_vma take a reference
to the root in anon_vma_fork. When the anon_vma is freed at munmap or
process exit, we drop the refcount in anon_vma_unlink and possibly free
the root anon_vma.
The KSM anon_vma reference count function also needs to be modified to
deal with the possibility of freeing 2 levels of anon_vma. The easiest
way to do this is to break out the KSM magic and make it generic.
When compiling without CONFIG_KSM, this code is compiled out.
Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Always (and only) lock the root (oldest) anon_vma whenever we do something
in an anon_vma. The recently introduced anon_vma scalability is due to
the rmap code scanning only the VMAs that need to be scanned. Many common
operations still took the anon_vma lock on the root anon_vma, so always
taking that lock is not expected to introduce any scalability issues.
However, always taking the same lock does mean we only need to take one
lock, which means rmap_walk on pages from any anon_vma in the vma is
excluded from occurring during an munmap, expand_stack or other operation
that needs to exclude rmap_walk and similar functions.
Also add the proper locking to vma_adjust.
Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Track the root (oldest) anon_vma in each anon_vma tree. Because we only
take the lock on the root anon_vma, we cannot use the lock on higher-up
anon_vmas to lock anything. This makes it impossible to do an indirect
lookup of the root anon_vma, since the data structures could go away from
under us.
However, a direct pointer is safe because the root anon_vma is always the
last one that gets freed on munmap or exit, by virtue of the same_vma list
order and unlink_anon_vmas walking the list forward.
[akpm@linux-foundation.org: fix typo]
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Subsitute a direct call of spin_lock(anon_vma->lock) with an inline
function doing exactly the same.
This makes it easier to do the substitution to the root anon_vma lock in a
following patch.
We will deal with the handful of special locks (nested, dec_and_lock, etc)
separately.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rename anon_vma_lock to vma_lock_anon_vma. This matches the naming style
used in page_lock_anon_vma and will come in really handy further down in
this patch series.
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a copy-on-write occurs, we take one of two paths in handle_mm_fault:
through handle_pte_fault for normal pages, or through hugetlb_fault for
huge pages.
In the normal page case, we eventually get to do_wp_page and call mmu
notifiers via ptep_clear_flush_notify. There is no callout to the mmmu
notifiers in the huge page case. This patch fixes that.
Signed-off-by: Doug Doan <dougd@cray.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Provide an INIT_MM_CONTEXT intializer macro which can be used to
statically initialize mm_struct:mm_context of init_mm. This way we can
get rid of code which will do the initialization at run time (on s390).
In addition the current code can be found at a place where it is not
expected. So let's have a common initializer which architectures
can use if needed.
This is based on a patch from Suzuki Poulose.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Suzuki Poulose <suzuki@in.ibm.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use ERR_CAST(x) rather than ERR_PTR(PTR_ERR(x)). The former makes more
clear what is the purpose of the operation, which otherwise looks like a
no-op.
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@
type T;
T x;
identifier f;
@@
T f (...) { <+...
- ERR_PTR(PTR_ERR(x))
+ x
...+> }
@@
expression x;
@@
- ERR_PTR(PTR_ERR(x))
+ ERR_CAST(x)
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use memdup_user when user data is immediately copied into the
allocated region.
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@
expression from,to,size,flag;
position p;
identifier l1,l2;
@@
- to = \(kmalloc@p\|kzalloc@p\)(size,flag);
+ to = memdup_user(from,size);
if (
- to==NULL
+ IS_ERR(to)
|| ...) {
<+... when != goto l1;
- -ENOMEM
+ PTR_ERR(to)
...+>
}
- if (copy_from_user(to, from, size) != 0) {
- <+... when != goto l2;
- -EFAULT
- ...+>
- }
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: 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>
Make sure we check the truncate constraints early on in ->setattr by adding
those checks to inode_change_ok. Also clean up and document inode_change_ok
to make this obvious.
As a fallout we don't have to call inode_newsize_ok from simple_setsize and
simplify it down to a truncate_setsize which doesn't return an error. This
simplifies a lot of setattr implementations and means we use truncate_setsize
almost everywhere. Get rid of fat_setsize now that it's trivial and mark
ext2_setsize static to make the calling convention obvious.
Keep the inode_newsize_ok in vmtruncate for now as all callers need an
audit for its removal anyway.
Note: setattr code in ecryptfs doesn't call inode_change_ok at all and
needs a deeper audit, but that is left for later.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make sure we call inode_change_ok before doing any changes in ->setattr,
and make sure to call it even if our fs wants to ignore normal UNIX
permissions, but use the ATTR_FORCE to skip those.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Despite its name it's now a generic implementation of ->setattr, but
rather a helper to copy attributes from a struct iattr to the inode.
Rename it to setattr_copy to reflect this fact.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This patch fixes alignment of slab objects in case CONFIG_DEBUG_PAGEALLOC is
active.
Before this spot in kmem_cache_create, we have this situation:
- align contains the required alignment of the object
- cachep->obj_offset is 0 or equals align in case of CONFIG_DEBUG_SLAB
- size equals the size of the object, or object plus trailing redzone in case
of CONFIG_DEBUG_SLAB
This spot tries to fill one page per object if the object is in certain size
limits, however setting obj_offset to PAGE_SIZE - size does break the object
alignment since size may not be aligned with the required alignment.
This patch simply adds an ALIGN(size, align) to the equation and fixes the
object size detection accordingly.
This code in drivers/s390/cio/qdio_setup_init has lead to incorrectly aligned
slab objects (sizeof(struct qdio_q) equals 1792):
qdio_q_cache = kmem_cache_create("qdio_q", sizeof(struct qdio_q),
256, 0, NULL);
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
All callers expect a boolean result which is true if the region
overlaps a reserved region. However, the implementation actually
returns -1 if there is no overlap, and a region index (0 based)
if there is.
Make it behave as callers (and common sense) expect.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Fix a bug where a lock is _bh nested within another _bh lock,
but forgets to use the _bh variant for unlock.
Further more, it's not necessary to test _bh locks, the inner lock
can just use spin_lock(). So fix up the bug by making that change.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This patch makes sure we first initialize everything and set the BDI_registered
flag, and only after this we add the bdi to 'bdi_list'. Current code adds the
bdi to the list too early, and as a result I the
WARN(!test_bit(BDI_registered, &bdi->state)
in bdi forker is triggered. Also, it is in general good practice to make things
visible only when they are fully initialized.
Also, this patch does few micro clean-ups:
1. Removes the 'exit' label which does not do anything, just returns. This
allows to get rid of few braces and 'ret' variable and make the code smaller.
2. If 'kthread_run()' fails, remove the error code it returns, not hard-coded
'-ENOMEM'. Theoretically, some day 'kthread_run()' can return something
else. Also, in case of failure it is not necessary to set 'bdi->wb.task' to
NULL.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Add 2 new trace points to the periodic write-back wake up case, just like we do
in the 'bdi_queue_work()' function. Namely, introduce:
1. trace_writeback_wake_thread(bdi)
2. trace_writeback_wake_forker_thread(bdi)
The first event is triggered every time we wake up a bdi thread to start
periodic background write-out. The second event is triggered only when the bdi
thread does not exist and should be created by the forker thread.
This patch was suggested by Dave Chinner and Christoph Hellwig.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
The 'setup_timer()' function also calls 'init_timer()', so the extra
'init_timer()' call is not needed. Indeed, 'setup_timer()' is basically
'init_timer()' plus callback function and data pointers initialization.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Whe the first inode for a bdi is marked dirty, we wake up the bdi thread which
should take care of the periodic background write-out. However, the write-out
will actually start only 'dirty_writeback_interval' centisecs later, so we can
delay the wake-up.
This change was requested by Nick Piggin who pointed out that if we delay the
wake-up, we weed out 2 unnecessary contex switches, which matters because
'__mark_inode_dirty()' is a hot-path function.
This patch introduces a new function - 'bdi_wakeup_thread_delayed()', which
sets up a timer to wake-up the bdi thread and returns. So the wake-up is
delayed.
We also delete the timer in bdi threads just before writing-back. And
synchronously delete it when unregistering bdi. At the unregister point the bdi
does not have any users, so no one can arm it again.
Since now we take 'bdi->wb_lock' in the timer, which can execute in softirq
context, we have to use 'spin_lock_bh()' for 'bdi->wb_lock'. This patch makes
this change as well.
This patch also moves the 'bdi_wb_init()' function down in the file to avoid
forward-declaration of 'bdi_wakeup_thread_delayed()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Finally, we can get rid of unnecessary wake-ups in bdi threads, which are very
bad for battery-driven devices.
There are two types of activities bdi threads do:
1. process bdi works from the 'bdi->work_list'
2. periodic write-back
So there are 2 sources of wake-up events for bdi threads:
1. 'bdi_queue_work()' - submits bdi works
2. '__mark_inode_dirty()' - adds dirty I/O to bdi's
The former already has bdi wake-up code. The latter does not, and this patch
adds it.
'__mark_inode_dirty()' is hot-path function, but this patch adds another
'spin_lock(&bdi->wb_lock)' there. However, it is taken only in rare cases when
the bdi has no dirty inodes. So adding this spinlock should be fine and should
not affect performance.
This patch makes sure bdi threads and the forker thread do not wake-up if there
is nothing to do. The forker thread will nevertheless wake up at least every
5 min. to check whether it has to kill a bdi thread. This can also be optimized,
but is not worth it.
This patch also tidies up the warning about unregistered bid, and turns it from
an ugly crocodile to a simple 'WARN()' statement.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently, bdi threads can decide to exit if there were no useful activities
for 5 minutes. However, this causes nasty races: we can easily oops in the
'bdi_queue_work()' if the bdi thread decides to exit while we are waking it up.
And even if we do not oops, but the bdi tread exits immediately after we wake
it up, we'd lose the wake-up event and have an unnecessary delay (up to 5 secs)
in the bdi work processing.
This patch makes the forker thread to be the central place which not only
creates bdi threads, but also kills them if they were inactive long enough.
This better design-wise.
Another reason why this change was done is to prepare for the further changes
which will prevent the bdi threads from waking up every 5 sec and wasting
power. Indeed, when the task does not wake up periodically anymore, it won't be
able to exit either.
This patch also moves the the 'wake_up_bit()' call from the bdi thread to the
forker thread as well. So now the forker thread sets the BDI_pending bit, then
forks the task or kills it, then clears the bit and wakes up the waiting
process.
The only process which may wain on the bit is 'bdi_wb_shutdown()'. This
function was changed as well - now it first removes the bdi from the
'bdi_list', then waits on the 'BDI_pending' bit. Once it wakes up, it is
guaranteed that the forker thread won't race with it, because the bdi is not
visible. Note, the forker thread sets the 'BDI_pending' bit under the
'bdi->wb_lock' which is essential for proper serialization.
And additionally, when we change 'bdi->wb.task', we now take the
'bdi->work_lock', to make sure that we do not lose wake-ups which we otherwise
would when raced with, say, 'bdi_queue_work()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This patch re-structures the bdi forker a little:
1. Add 'bdi_cap_flush_forker(bdi)' condition check to the bdi loop. The reason
for this is that the forker thread can start _before_ the 'BDI_registered'
flag is set (see 'bdi_register()'), so the WARN() statement will fire for
the default bdi. I observed this warning at boot-up.
2. Introduce an enum 'action' and use "switch" statement in the outer loop.
This is a preparation to the further patch which will teach the forker
thread killing bdi threads, so we'll have another case in the "switch"
statement. This change was suggested by Christoph Hellwig.
This patch is just a small step towards the coming change where the forker
thread will kill the bdi threads. It should simplify reviewing the following
changes, which would otherwise be larger.
This patch also amends comments a little.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
The forker thread removes bdis from 'bdi_list' before forking the bdi thread.
But this is wrong for at least 2 reasons.
Reason #1: if we temporary remove a bdi from the list, we may miss works which
would otherwise be given to us.
Reason #2: this is racy; indeed, 'bdi_wb_shutdown()' expects that bdis are
always in the 'bdi_list' (see 'bdi_remove_from_list()'), and when
it races with the forker thread, it can shut down the bdi thread
at the same time as the forker creates it.
This patch makes sure the forker thread never removes bdis from 'bdi_list'
(which was suggested by Christoph Hellwig).
In order to make sure that we do not race with 'bdi_wb_shutdown()', we have to
hold the 'bdi_lock' while walking the 'bdi_list' and setting the 'BDI_pending'
flag.
NOTE! The error path is interesting. Currently, when we fail to create a bdi
thread, we move the bdi to the tail of 'bdi_list'. But if we never remove the
bdi from the list, we cannot move it to the tail either, because then we can
mess up the RCU readers which walk the list. And also, we'll have the race
described above in "Reason #2".
But I not think that adding to the tail is any important so I just do not do
that.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This patch simplifies bdi code a little by removing the 'pending_list' which is
redundant. Indeed, currently the forker thread ('bdi_forker_thread()') is
working like this:
1. In a loop, fetch all bdi's which have works but have no writeback thread and
move them to the 'pending_list'.
2. If the list is empty, sleep for 5 sec.
3. Otherwise, take one bdi from the list, fork the writeback thread for this
bdi, and repeat the loop.
IOW, it first moves everything to the 'pending_list', then process only one
element, and so on. This patch simplifies the algorithm, which is now as
follows.
1. Find the first bdi which has a work and remove it from the global list of
bdi's (bdi_list).
2. If there was not such bdi, sleep 5 sec.
3. Fork the writeback thread for this bdi and repeat the loop.
IOW, now we find the first bdi to process, process it, and so on. This is
simpler and involves less lists.
The bonus now is that we can get rid of a couple of functions, as well as
remove complications which involve 'rcu_call()' and 'bdi->rcu_head'.
This patch also makes sure we use 'list_add_tail_rcu()', instead of plain
'list_add_tail()', but this piece of code is going to be removed in the next
patch anyway.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
