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authorHugh Dickins <hughd@google.com>2016-05-20 03:12:50 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-20 05:12:14 +0300
commit52b6f46bc163eef17ecba4cd552beeafe2b24453 (patch)
treef1f8a9dc258f548fcdb7fa63b9b9a5eebd17976f /include/linux/vmstat.h
parent9e18eb29356b7dfd55183bd42cf73919d1590835 (diff)
downloadlinux-52b6f46bc163eef17ecba4cd552beeafe2b24453.tar.xz
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 'include/linux/vmstat.h')
-rw-r--r--include/linux/vmstat.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 73fae8c4a5fb..02fce415b3d9 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -193,6 +193,10 @@ void quiet_vmstat(void);
void cpu_vm_stats_fold(int cpu);
void refresh_zone_stat_thresholds(void);
+struct ctl_table;
+int vmstat_refresh(struct ctl_table *, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+
void drain_zonestat(struct zone *zone, struct per_cpu_pageset *);
int calculate_pressure_threshold(struct zone *zone);