Tejun reported stuttering and latency spikes on a system where random
tasks would enter direct reclaim and get stuck on dirty pages. Around
50% of memory was occupied by tmpfs backed by an SSD, and another disk
(rotating) was reading and writing at max speed to shrink a partition.
: The problem was pretty ridiculous. It's a 8gig machine w/ one ssd and 10k
: rpm harddrive and I could reliably reproduce constant stuttering every
: several seconds for as long as buffered IO was going on on the hard drive
: either with tmpfs occupying somewhere above 4gig or a test program which
: allocates about the same amount of anon memory. Although swap usage was
: zero, turning off swap also made the problem go away too.
:
: The trigger conditions seem quite plausible - high anon memory usage w/
: heavy buffered IO and swap configured - and it's highly likely that this
: is happening in the wild too. (this can happen with copying large files
: to usb sticks too, right?)
This patch (of 2):
The dirty_balance_reserve is an approximation of the fraction of free
pages that the page allocator does not make available for page cache
allocations. As a result, it has to be taken into account when
calculating the amount of "dirtyable memory", the baseline to which
dirty_background_ratio and dirty_ratio are applied.
However, currently the reserve is subtracted from the sum of free and
reclaimable pages, which is non-sensical and leads to erroneous results
when the system is dominated by unreclaimable pages and the
dirty_balance_reserve is bigger than free+reclaimable. In that case, at
least the already allocated cache should be considered dirtyable.
Fix the calculation by subtracting the reserve from the amount of free
pages, then adding the reclaimable pages on top.
[akpm@linux-foundation.org: fix CONFIG_HIGHMEM build]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Tejun Heo <tj@kernel.org>
Tested-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Toralf runs trinity on UML/i386. After some time it hangs and the last
message line is
BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child0:1521]
It's found that pages_dirtied becomes very large. More than 1000000000
pages in this case:
period = HZ * pages_dirtied / task_ratelimit;
BUG_ON(pages_dirtied > 2000000000);
BUG_ON(pages_dirtied > 1000000000); <---------
UML debug printf shows that we got negative pause here:
ick: pause : -984
ick: pages_dirtied : 0
ick: task_ratelimit: 0
pause:
+ if (pause < 0) {
+ extern int printf(char *, ...);
+ printf("ick : pause : %li\n", pause);
+ printf("ick: pages_dirtied : %lu\n", pages_dirtied);
+ printf("ick: task_ratelimit: %lu\n", task_ratelimit);
+ BUG_ON(1);
+ }
trace_balance_dirty_pages(bdi,
Since pause is bounded by [min_pause, max_pause] where min_pause is also
bounded by max_pause. It's suspected and demonstrated that the
max_pause calculation goes wrong:
ick: pause : -717
ick: min_pause : -177
ick: max_pause : -717
ick: pages_dirtied : 14
ick: task_ratelimit: 0
The problem lies in the two "long = unsigned long" assignments in
bdi_max_pause() which might go negative if the highest bit is 1, and the
min_t(long, ...) check failed to protect it falling under 0. Fix all of
them by using "unsigned long" throughout the function.
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Tested-by: Toralf Förster <toralf.foerster@gmx.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Richard Weinberger <richard@nod.at>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add memcg routines to count writeback pages, later dirty pages will also
be accounted.
After Kame's commit 89c06bd52f ("memcg: use new logic for page stat
accounting"), we can use 'struct page' flag to test page state instead
of per page_cgroup flag. But memcg has a feature to move a page from a
cgroup to another one and may have race between "move" and "page stat
accounting". So in order to avoid the race we have designed a new lock:
mem_cgroup_begin_update_page_stat()
modify page information -->(a)
mem_cgroup_update_page_stat() -->(b)
mem_cgroup_end_update_page_stat()
It requires both (a) and (b)(writeback pages accounting) to be pretected
in mem_cgroup_{begin/end}_update_page_stat(). It's full no-op for
!CONFIG_MEMCG, almost no-op if memcg is disabled (but compiled in), rcu
read lock in the most cases (no task is moving), and spin_lock_irqsave
on top in the slow path.
There're two writeback interfaces to modify: test_{clear/set}_page_writeback().
And the lock order is:
--> memcg->move_lock
--> mapping->tree_lock
Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Greg Thelen <gthelen@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The feature prevents mistrusted filesystems (ie: FUSE mounts created by
unprivileged users) to grow a large number of dirty pages before
throttling. For such filesystems balance_dirty_pages always check bdi
counters against bdi limits. I.e. even if global "nr_dirty" is under
"freerun", it's not allowed to skip bdi checks. The only use case for now
is fuse: it sets bdi max_ratio to 1% by default and system administrators
are supposed to expect that this limit won't be exceeded.
The feature is on if a BDI is marked by BDI_CAP_STRICTLIMIT flag. A
filesystem may set the flag when it initializes its BDI.
The problematic scenario comes from the fact that nobody pays attention to
the NR_WRITEBACK_TEMP counter (i.e. number of pages under fuse
writeback). The implementation of fuse writeback releases original page
(by calling end_page_writeback) almost immediately. A fuse request queued
for real processing bears a copy of original page. Hence, if userspace
fuse daemon doesn't finalize write requests in timely manner, an
aggressive mmap writer can pollute virtually all memory by those temporary
fuse page copies. They are carefully accounted in NR_WRITEBACK_TEMP, but
nobody cares.
To make further explanations shorter, let me use "NR_WRITEBACK_TEMP
problem" as a shortcut for "a possibility of uncontrolled grow of amount
of RAM consumed by temporary pages allocated by kernel fuse to process
writeback".
The problem was very easy to reproduce. There is a trivial example
filesystem implementation in fuse userspace distribution: fusexmp_fh.c. I
added "sleep(1);" to the write methods, then recompiled and mounted it.
Then created a huge file on the mount point and run a simple program which
mmap-ed the file to a memory region, then wrote a data to the region. An
hour later I observed almost all RAM consumed by fuse writeback. Since
then some unrelated changes in kernel fuse made it more difficult to
reproduce, but it is still possible now.
Putting this theoretical happens-in-the-lab thing aside, there is another
thing that really hurts real world (FUSE) users. This is write-through
page cache policy FUSE currently uses. I.e. handling write(2), kernel
fuse populates page cache and flushes user data to the server
synchronously. This is excessively suboptimal. Pavel Emelyanov's patches
("writeback cache policy") solve the problem, but they also make resolving
NR_WRITEBACK_TEMP problem absolutely necessary. Otherwise, simply copying
a huge file to a fuse mount would result in memory starvation. Miklos,
the maintainer of FUSE, believes strictlimit feature the way to go.
And eventually putting FUSE topics aside, there is one more use-case for
strictlimit feature. Using a slow USB stick (mass storage) in a machine
with huge amount of RAM installed is a well-known pain. Let's make simple
computations. Assuming 64GB of RAM installed, existing implementation of
balance_dirty_pages will start throttling only after 9.6GB of RAM becomes
dirty (freerun == 15% of total RAM). So, the command "cp 9GB_file
/media/my-usb-storage/" may return in a few seconds, but subsequent
"umount /media/my-usb-storage/" will take more than two hours if effective
throughput of the storage is, to say, 1MB/sec.
After inclusion of strictlimit feature, it will be trivial to add a knob
(e.g. /sys/devices/virtual/bdi/x:y/strictlimit) to enable it on demand.
Manually or via udev rule. May be I'm wrong, but it seems to be quite a
natural desire to limit the amount of dirty memory for some devices we are
not fully trust (in the sense of sustainable throughput).
[akpm@linux-foundation.org: fix warning in page-writeback.c]
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch is based on KOSAKI's work and I add a little more description,
please refer https://lkml.org/lkml/2012/6/14/74.
Currently, I found system can enter a state that there are lots of free
pages in a zone but only order-0 and order-1 pages which means the zone is
heavily fragmented, then high order allocation could make direct reclaim
path's long stall(ex, 60 seconds) especially in no swap and no compaciton
enviroment. This problem happened on v3.4, but it seems issue still lives
in current tree, the reason is do_try_to_free_pages enter live lock:
kswapd will go to sleep if the zones have been fully scanned and are still
not balanced. As kswapd thinks there's little point trying all over again
to avoid infinite loop. Instead it changes order from high-order to
0-order because kswapd think order-0 is the most important. Look at
73ce02e9 in detail. If watermarks are ok, kswapd will go back to sleep
and may leave zone->all_unreclaimable =3D 0. It assume high-order users
can still perform direct reclaim if they wish.
Direct reclaim continue to reclaim for a high order which is not a
COSTLY_ORDER without oom-killer until kswapd turn on
zone->all_unreclaimble= . This is because to avoid too early oom-kill.
So it means direct_reclaim depends on kswapd to break this loop.
In worst case, direct-reclaim may continue to page reclaim forever when
kswapd sleeps forever until someone like watchdog detect and finally kill
the process. As described in:
http://thread.gmane.org/gmane.linux.kernel.mm/103737
We can't turn on zone->all_unreclaimable from direct reclaim path because
direct reclaim path don't take any lock and this way is racy. Thus this
patch removes zone->all_unreclaimable field completely and recalculates
zone reclaimable state every time.
Note: we can't take the idea that direct-reclaim see zone->pages_scanned
directly and kswapd continue to use zone->all_unreclaimable. Because, it
is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use
zone->all_unreclaimable as a name) describes the detail.
[akpm@linux-foundation.org: uninline zone_reclaimable_pages() and zone_reclaimable()]
Cc: Aaditya Kumar <aaditya.kumar.30@gmail.com>
Cc: Ying Han <yinghan@google.com>
Cc: Nick Piggin <npiggin@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Bob Liu <lliubbo@gmail.com>
Cc: Neil Zhang <zhangwm@marvell.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Lisa Du <cldu@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts commit 75f7ad8e04. It was the result of a problem
observed with a 3.2 kernel and merged in 3.9, while the issue had been
resolved upstream in 3.3 (commit ab8fabd46f: "mm: exclude reserved
pages from dirtyable memory").
The "reserved pages" are a superset of min_free_kbytes, thus this change
is redundant and confusing. Revert it.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Paul Szabo <psz@maths.usyd.edu.au>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications. For example, the fix in
commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.
After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out. Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.
This removes all the uses of the __cpuinit macros from C files in
the core kernel directories (kernel, init, lib, mm, and include)
that don't really have a specific maintainer.
[1] https://lkml.org/lkml/2013/5/20/589
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Walking a bio's page mappings has proved problematic, so create a new
bio flag to indicate that a bio's data needs to be snapshotted in order
to guarantee stable pages during writeback. Next, for the one user
(ext3/jbd) of snapshotting, hook all the places where writes can be
initiated without PG_writeback set, and set BIO_SNAP_STABLE there.
We must also flag journal "metadata" bios for stable writeout, since
file data can be written through the journal. Finally, the
MS_SNAP_STABLE mount flag (only used by ext3) is now superfluous, so get
rid of it.
[akpm@linux-foundation.org: rename _submit_bh()'s `flags' to `bio_flags', delobotomize the _submit_bh declaration]
[akpm@linux-foundation.org: teeny cleanup]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull writeback fixes from Wu Fengguang:
"Two writeback fixes
- fix negative (setpoint - dirty) in 32bit archs
- use down_read_trylock() in writeback_inodes_sb(_nr)_if_idle()"
* tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux:
Negative (setpoint-dirty) in bdi_position_ratio()
vfs: re-implement writeback_inodes_sb(_nr)_if_idle() and rename them
Pull block IO core bits from Jens Axboe:
"Below are the core block IO bits for 3.9. It was delayed a few days
since my workstation kept crashing every 2-8h after pulling it into
current -git, but turns out it is a bug in the new pstate code (divide
by zero, will report separately). In any case, it contains:
- The big cfq/blkcg update from Tejun and and Vivek.
- Additional block and writeback tracepoints from Tejun.
- Improvement of the should sort (based on queues) logic in the plug
flushing.
- _io() variants of the wait_for_completion() interface, using
io_schedule() instead of schedule() to contribute to io wait
properly.
- Various little fixes.
You'll get two trivial merge conflicts, which should be easy enough to
fix up"
Fix up the trivial conflicts due to hlist traversal cleanups (commit
b67bfe0d42: "hlist: drop the node parameter from iterators").
* 'for-3.9/core' of git://git.kernel.dk/linux-block: (39 commits)
block: remove redundant check to bd_openers()
block: use i_size_write() in bd_set_size()
cfq: fix lock imbalance with failed allocations
drivers/block/swim3.c: fix null pointer dereference
block: don't select PERCPU_RWSEM
block: account iowait time when waiting for completion of IO request
sched: add wait_for_completion_io[_timeout]
writeback: add more tracepoints
block: add block_{touch|dirty}_buffer tracepoint
buffer: make touch_buffer() an exported function
block: add @req to bio_{front|back}_merge tracepoints
block: add missing block_bio_complete() tracepoint
block: Remove should_sort judgement when flush blk_plug
block,elevator: use new hashtable implementation
cfq-iosched: add hierarchical cfq_group statistics
cfq-iosched: collect stats from dead cfqgs
cfq-iosched: separate out cfqg_stats_reset() from cfq_pd_reset_stats()
blkcg: make blkcg_print_blkgs() grab q locks instead of blkcg lock
block: RCU free request_queue
blkcg: implement blkg_[rw]stat_recursive_sum() and blkg_[rw]stat_merge()
...
When calculating amount of dirtyable memory, min_free_kbytes should be
subtracted because it is not intended for dirty pages.
Addresses http://bugs.debian.org/695182
[akpm@linux-foundation.org: fix up min_free_kbytes extern declarations]
[akpm@linux-foundation.org: fix min() warning]
Signed-off-by: Paul Szabo <psz@maths.usyd.edu.au>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This provides a band-aid to provide stable page writes on jbd without
needing to backport the fixed locking and page writeback bit handling
schemes of jbd2. The band-aid works by using bounce buffers to snapshot
page contents instead of waiting.
For those wondering about the ext3 bandage -- fixing the jbd locking
(which was done as part of ext4dev years ago) is a lot of surgery, and
setting PG_writeback on data pages when we actually hold the page lock
dropped ext3 performance by nearly an order of magnitude. If we're
going to migrate iscsi and raid to use stable page writes, the
complaints about high latency will likely return. We might as well
centralize their page snapshotting thing to one place.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Tested-by: Andy Lutomirski <luto@amacapital.net>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Create a helper function to check if a backing device requires stable
page writes and, if so, performs the necessary wait. Then, make it so
that all points in the memory manager that handle making pages writable
use the helper function. This should provide stable page write support
to most filesystems, while eliminating unnecessary waiting for devices
that don't require the feature.
Before this patchset, all filesystems would block, regardless of whether
or not it was necessary. ext3 would wait, but still generate occasional
checksum errors. The network filesystems were left to do their own
thing, so they'd wait too.
After this patchset, all the disk filesystems except ext3 and btrfs will
wait only if the hardware requires it. ext3 (if necessary) snapshots
pages instead of blocking, and btrfs provides its own bdi so the mm will
never wait. Network filesystems haven't been touched, so either they
provide their own stable page guarantees or they don't block at all.
The blocking behavior is back to what it was before 3.0 if you don't
have a disk requiring stable page writes.
Here's the result of using dbench to test latency on ext2:
3.8.0-rc3:
Operation Count AvgLat MaxLat
----------------------------------------
WriteX 109347 0.028 59.817
ReadX 347180 0.004 3.391
Flush 15514 29.828 287.283
Throughput 57.429 MB/sec 4 clients 4 procs max_latency=287.290 ms
3.8.0-rc3 + patches:
WriteX 105556 0.029 4.273
ReadX 335004 0.005 4.112
Flush 14982 30.540 298.634
Throughput 55.4496 MB/sec 4 clients 4 procs max_latency=298.650 ms
As you can see, the maximum write latency drops considerably with this
patch enabled. The other filesystems (ext3/ext4/xfs/btrfs) behave
similarly, but see the cover letter for those results.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In bdi_position_ratio(), get difference (setpoint-dirty) right even when
negative. Both setpoint and dirty are unsigned long, the difference was
zero-padded thus wrongly sign-extended to s64. This issue affects all
32-bit architectures, does not affect 64-bit architectures where long
and s64 are equivalent.
In this function, dirty is between freerun and limit, the pseudo-float x
is between [-1,1], expected to be negative about half the time. With
zero-padding, instead of a small negative x we obtained a large positive
one so bdi_position_ratio() returned garbage.
Casting the difference to s64 also prevents overflow with left-shift;
though normally these numbers are small and I never observed a 32-bit
overflow there.
(This patch does not solve the PAE OOM issue.)
Paul Szabo psz@maths.usyd.edu.auhttp://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics University of Sydney Australia
Reviewed-by: Jan Kara <jack@suse.cz>
Reported-by: Paul Szabo <psz@maths.usyd.edu.au>
Reference: http://bugs.debian.org/695182
Signed-off-by: Paul Szabo <psz@maths.usyd.edu.au>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Add tracepoints for page dirtying, writeback_single_inode start, inode
dirtying and writeback. For the latter two inode events, a pair of
events are defined to denote start and end of the operations (the
starting one has _start suffix and the one w/o suffix happens after
the operation is complete). These inode ops are FS specific and can
be non-trivial and having enclosing tracepoints is useful for external
tracers.
This is part of tracepoint additions to improve visiblity into
dirtying / writeback operations for io tracer and userland.
v2: writeback_dirty_inode[_start] TPs may be called for files on
pseudo FSes w/ unregistered bdi. Check whether bdi->dev is %NULL
before dereferencing.
v3: buffer dirtying moved to a block TP.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The system uses global_dirtyable_memory() to calculate number of
dirtyable pages/pages that can be allocated to the page cache. A bug
causes an underflow thus making the page count look like a big unsigned
number. This in turn confuses the dirty writeback throttling to
aggressively write back pages as they become dirty (usually 1 page at a
time). This generally only affects systems with highmem because the
underflowed count gets subtracted from the global count of dirtyable
memory.
The problem was introduced with v3.2-4896-gab8fabd
Fix is to ensure we don't get an underflowed total of either highmem or
global dirtyable memory.
Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Puneet Kumar <puneetster@chromium.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Damien Wyart <damien.wyart@free.fr>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The CPU hotplug callback related to writeback calls writeback_set_ratelimit()
during every state change in the hotplug sequence. This is unnecessary
since num_online_cpus() changes only once during the entire hotplug operation.
So invoke the function only once per hotplug, thereby avoiding the
unnecessary repetition of those costly calculations.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Finally we can kill the 'sync_supers' kernel thread along with the
'->write_super()' superblock operation because all the users are gone.
Now every file-system is supposed to self-manage own superblock and
its dirty state.
The nice thing about killing this thread is that it improves power management.
Indeed, 'sync_supers' is a source of monotonic system wake-ups - it woke up
every 5 seconds no matter what - even if there were no dirty superblocks and
even if there were no file-systems using this service (e.g., btrfs and
journalled ext4 do not need it). So it was wasting power most of the time. And
because the thread was in the core of the kernel, all systems had to have it.
So I am quite happy to make it go away.
Interestingly, this thread is a left-over from the pdflush kernel thread which
was a self-forking kernel thread responsible for all the write-back in old
Linux kernels. It was turned into per-block device BDI threads, and
'sync_supers' was a left-over. Thus, R.I.P, pdflush as well.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Convert calculations of proportion of writeback each bdi does to new flexible
proportion code. That allows us to use aging period of fixed wallclock time
which gives better proportion estimates given the hugely varying throughput of
different devices.
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
This prevents global_dirty_limit from remaining 0 (the initial value)
for long time, since it's only updated in update_dirty_limit() when
above the dirty freerun area.
It will avoid unexpected consequences when some random code use it as a
convenient approximation of the global dirty threshold.
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
The function global_dirtyable_memory is only referenced in this file and
should be marked static to prevent it from being exposed globally.
This quiets the sparse warning:
warning: symbol 'global_dirtyable_memory' was not declared. Should it be static?
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Pull ext4 updates for 3.4 from Ted Ts'o:
"Ext4 commits for 3.3 merge window; mostly cleanups and bug fixes
The changes to export dirty_writeback_interval are from Artem's s_dirt
cleanup patch series. The same is true of the change to remove the
s_dirt helper functions which never got used by anyone in-tree. I've
run these changes by Al Viro, and am carrying them so that Artem can
more easily fix up the rest of the file systems during the next merge
window. (Originally we had hopped to remove the use of s_dirt from
ext4 during this merge window, but his patches had some bugs, so I
ultimately ended dropping them from the ext4 tree.)"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (66 commits)
vfs: remove unused superblock helpers
mm: export dirty_writeback_interval
ext4: remove useless s_dirt assignment
ext4: write superblock only once on unmount
ext4: do not mark superblock as dirty unnecessarily
ext4: correct ext4_punch_hole return codes
ext4: remove restrictive checks for EOFBLOCKS_FL
ext4: always set then trimmed blocks count into len
ext4: fix trimmed block count accunting
ext4: fix start and len arguments handling in ext4_trim_fs()
ext4: update s_free_{inodes,blocks}_count during online resize
ext4: change some printk() calls to use ext4_msg() instead
ext4: avoid output message interleaving in ext4_error_<foo>()
ext4: remove trailing newlines from ext4_msg() and ext4_error() messages
ext4: add no_printk argument validation, fix fallout
ext4: remove redundant "EXT4-fs: " from uses of ext4_msg
ext4: give more helpful error message in ext4_ext_rm_leaf()
ext4: remove unused code from ext4_ext_map_blocks()
ext4: rewrite punch hole to use ext4_ext_remove_space()
jbd2: cleanup journal tail after transaction commit
...
Johannes Weiner
Fengguang Wu
Sha Zhengju
Maxim Patlasov
Lisa Du
Paul Gortmaker
Darrick J. Wong
Linus Torvalds
Paul Szabo
Clark Williams
paul.szabo@sydney.edu.au
Tejun Heo
Sonny Rao
Namjae Jeon
Srivatsa S. Bhat
Artem Bityutskiy
Wanpeng Li
Jan Kara
H Hartley Sweeten