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SubjectRe: [PATCH v2] mm: vmscan: fix the page state calculation in too_many_isolated
On 01/16/2015 06:47 AM, Andrew Morton wrote:

> From: Andrew Morton <akpm@linux-foundation.org>
> Subject: mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated-fix
>
> Move the zone_page_state_snapshot() fallback logic into
> too_many_isolated(), so shrink_inactive_list() doesn't incorrectly call
> congestion_wait().
>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Michal Hocko <mhocko@suse.cz>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Vinayak Menon <vinmenon@codeaurora.org>
> Cc: Vladimir Davydov <vdavydov@parallels.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> mm/vmscan.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff -puN mm/vmscan.c~mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated-fix mm/vmscan.c
> --- a/mm/vmscan.c~mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated-fix
> +++ a/mm/vmscan.c
> @@ -1402,7 +1402,7 @@ int isolate_lru_page(struct page *page)
> }
>
> static int __too_many_isolated(struct zone *zone, int file,
> - struct scan_control *sc, int safe)
> + struct scan_control *sc, int safe)
> {
> unsigned long inactive, isolated;
>
> @@ -1435,7 +1435,7 @@ static int __too_many_isolated(struct zo
> * unnecessary swapping, thrashing and OOM.
> */
> static int too_many_isolated(struct zone *zone, int file,
> - struct scan_control *sc, int safe)
> + struct scan_control *sc)
> {
> if (current_is_kswapd())
> return 0;
> @@ -1443,12 +1443,14 @@ static int too_many_isolated(struct zone
> if (!global_reclaim(sc))
> return 0;
>
> - if (unlikely(__too_many_isolated(zone, file, sc, 0))) {
> - if (safe)
> - return __too_many_isolated(zone, file, sc, safe);
> - else
> - return 1;
> - }
> + /*
> + * __too_many_isolated(safe=0) is fast but inaccurate, because it
> + * doesn't account for the vm_stat_diff[] counters. So if it looks
> + * like too_many_isolated() is about to return true, fall back to the
> + * slower, more accurate zone_page_state_snapshot().
> + */
> + if (unlikely(__too_many_isolated(zone, file, sc, 0)))
> + return __too_many_isolated(zone, file, sc, safe);

Just noticed now that, in the above statement it should be "1", instead
of "safe". "safe" is not declared.



--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
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