diff options
| author | Vinayak Menon <vinmenon@codeaurora.org> | 2017-02-19 20:00:30 +1100 |
|---|---|---|
| committer | Vinayak Menon <vinmenon@codeaurora.org> | 2017-02-20 12:12:11 +0530 |
| commit | 9dd531d8e96093e526154d51b67f55686d4da1de (patch) | |
| tree | c783fc5dc1049639ae35a8dd05cf64bb7c2dee6c | |
| parent | 3ba1a36ad812171629b91f5a49e486b2529c22a2 (diff) | |
mm: vmpressure: fix sending wrong events on underflow
At the end of a window period, if the reclaimed pages is greater than
scanned, an unsigned underflow can result in a huge pressure value and
thus a critical event. Reclaimed pages is found to go higher than scanned
because of the addition of reclaimed slab pages to reclaimed in
shrink_node without a corresponding increment to scanned pages. Minchan
Kim mentioned that this can also happen in the case of a THP page where
the scanned is 1 and reclaimed could be 512.
Link: http://lkml.kernel.org/r/1486641577-11685-1-git-send-email-vinmenon@codeaurora.org
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Shiraz Hashim <shashim@codeaurora.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Change-Id: Ic1221fa129c9b3512127537d62df7bd4a7606d24
Git-commit: 746d8d8f3ebb49a62ffcffb4b1f41cc27d020a2e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
| -rw-r--r-- | mm/vmpressure.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/mm/vmpressure.c b/mm/vmpressure.c index f514dc40dab1..f5383e43597a 100644 --- a/mm/vmpressure.c +++ b/mm/vmpressure.c @@ -149,9 +149,16 @@ static unsigned long vmpressure_calc_pressure(unsigned long scanned, unsigned long reclaimed) { unsigned long scale = scanned + reclaimed; - unsigned long pressure; + unsigned long pressure = 0; /* + * reclaimed can be greater than scanned in cases + * like THP, where the scanned is 1 and reclaimed + * could be 512 + */ + if (reclaimed >= scanned) + goto out; + /* * We calculate the ratio (in percents) of how many pages were * scanned vs. reclaimed in a given time frame (window). Note that * time is in VM reclaimer's "ticks", i.e. number of pages @@ -161,6 +168,7 @@ static unsigned long vmpressure_calc_pressure(unsigned long scanned, pressure = scale - (reclaimed * scale / scanned); pressure = pressure * 100 / scale; +out: pr_debug("%s: %3lu (s: %lu r: %lu)\n", __func__, pressure, scanned, reclaimed); |