diff options
| author | Hugh Dickins | 2016-05-19 17:12:50 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2016-05-19 19:12:14 -0700 |
| commit | 52b6f46bc163eef17ecba4cd552beeafe2b24453 (patch) | |
| tree | f1f8a9dc258f548fcdb7fa63b9b9a5eebd17976f /kernel/sysctl.c | |
| parent | 9e18eb29356b7dfd55183bd42cf73919d1590835 (diff) | |
mm: /proc/sys/vm/stat_refresh to force vmstat update
Provide /proc/sys/vm/stat_refresh to force an immediate update of
per-cpu into global vmstats: useful to avoid a sleep(2) or whatever
before checking counts when testing. Originally added to work around a
bug which left counts stranded indefinitely on a cpu going idle (an
inaccuracy magnified when small below-batch numbers represent "huge"
amounts of memory), but I believe that bug is now fixed: nonetheless,
this is still a useful knob.
Its schedule_on_each_cpu() is probably too expensive just to fold into
reading /proc/meminfo itself: give this mode 0600 to prevent abuse.
Allow a write or a read to do the same: nothing to read, but "grep -h
Shmem /proc/sys/vm/stat_refresh /proc/meminfo" is convenient. Oh, and
since global_page_state() itself is careful to disguise any underflow as
0, hack in an "Invalid argument" and pr_warn() if a counter is negative
after the refresh - this helped to fix a misaccounting of
NR_ISOLATED_FILE in my migration code.
But on recent kernels, I find that NR_ALLOC_BATCH and NR_PAGES_SCANNED
often go negative some of the time. I have not yet worked out why, but
have no evidence that it's actually harmful. Punt for the moment by
just ignoring the anomaly on those.
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Ning Qu <quning@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
| -rw-r--r-- | kernel/sysctl.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c index c8b318663525..2effd84d83e3 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1521,6 +1521,13 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, + { + .procname = "stat_refresh", + .data = NULL, + .maxlen = 0, + .mode = 0600, + .proc_handler = vmstat_refresh, + }, #endif #ifdef CONFIG_MMU { |