From: Christoph Lameter <cl@linux-foundation.org>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mel@csn.ul.ie>, Rik van Riel <riel@redhat.com>,
Minchan Kim <minchan.kim@gmail.com>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 2/2] vmscan: don't subtraction of unsined
Date: Fri, 25 Jun 2010 09:17:03 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1006250912380.18900@router.home> (raw)
In-Reply-To: <20100625202126.806A.A69D9226@jp.fujitsu.com>
On Fri, 25 Jun 2010, KOSAKI Motohiro wrote:
> 'slab_reclaimable' and 'nr_pages' are unsigned. so, subtraction is
> unsafe.
Why? We are subtracting the current value of NR_SLAB_RECLAIMABLE from the
earlier one. The result can be negative (maybe concurrent allocations) and
then the nr_reclaimed gets decremented instead. This is okay since we
have not reached our goal then of reducing the number of reclaimable slab
pages on the zone.
> @@ -2622,17 +2624,21 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
> * Note that shrink_slab will free memory on all zones and may
> * take a long time.
> */
> - while (shrink_slab(sc.nr_scanned, gfp_mask, lru_pages) &&
> - zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
> - slab_reclaimable - nr_pages)
The comparison could be a problem here. So
zone_page_state(zone, NR_SLAB_RECLAIMABLE) + nr_pages >
slab_reclaimable
?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2010-06-25 14:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-25 11:21 [PATCH 1/2] vmscan: shrink_slab() require number of lru_pages, not page order KOSAKI Motohiro
2010-06-25 11:23 ` [PATCH 2/2] vmscan: don't subtraction of unsined KOSAKI Motohiro
2010-06-25 14:17 ` Christoph Lameter [this message]
2010-06-28 2:26 ` KOSAKI Motohiro
2010-06-29 15:14 ` Christoph Lameter
2010-06-25 14:07 ` [PATCH 1/2] vmscan: shrink_slab() require number of lru_pages, not page order Christoph Lameter
2010-06-27 1:03 ` Minchan Kim
2010-06-29 15:19 ` Christoph Lameter
2010-06-28 1:32 ` KOSAKI Motohiro
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.00.1006250912380.18900@router.home \
--to=cl@linux-foundation.org \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
--cc=minchan.kim@gmail.com \
--cc=riel@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox