lkml.org 
[lkml]   [2011]   [May]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] mm: vmscan: Correctly check if reclaimer should schedule during shrink_slab
From
On Wed, May 18, 2011 at 1:15 AM, Mel Gorman <mgorman@suse.de> wrote:
> It has been reported on some laptops that kswapd is consuming large
> amounts of CPU and not being scheduled when SLUB is enabled during
> large amounts of file copying. It is expected that this is due to
> kswapd missing every cond_resched() point because;
>
> shrink_page_list() calls cond_resched() if inactive pages were isolated
>        which in turn may not happen if all_unreclaimable is set in
>        shrink_zones(). If for whatver reason, all_unreclaimable is
>        set on all zones, we can miss calling cond_resched().
>
> balance_pgdat() only calls cond_resched if the zones are not
>        balanced. For a high-order allocation that is balanced, it
>        checks order-0 again. During that window, order-0 might have
>        become unbalanced so it loops again for order-0 and returns
>        that it was reclaiming for order-0 to kswapd(). It can then
>        find that a caller has rewoken kswapd for a high-order and
>        re-enters balance_pgdat() without ever calling cond_resched().
>
> shrink_slab only calls cond_resched() if we are reclaiming slab
>        pages. If there are a large number of direct reclaimers, the
>        shrinker_rwsem can be contended and prevent kswapd calling
>        cond_resched().
>
> This patch modifies the shrink_slab() case. If the semaphore is
> contended, the caller will still check cond_resched(). After each
> successful call into a shrinker, the check for cond_resched() is
> still necessary in case one shrinker call is particularly slow.
>
> This patch replaces
> mm-vmscan-if-kswapd-has-been-running-too-long-allow-it-to-sleep.patch
> in -mm.
>
> [mgorman@suse.de: Preserve call to cond_resched after each call into shrinker]
> From: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> Signed-off-by: Mel Gorman <mgorman@suse.de>

--
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-05-19 02:05    [W:0.191 / U:0.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site