From: Minchan Kim <minchan.kim@gmail.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, jweiner@redhat.com, mel@csn.ul.ie,
riel@redhat.com, lee.schermerhorn@hp.com
Subject: Re: [PATCH] vmscan: add barrier to prevent evictable page in unevictable list
Date: Wed, 28 Sep 2011 11:25:10 +0900 [thread overview]
Message-ID: <20110928022510.GB12100@barrios-desktop> (raw)
In-Reply-To: <4E8284C6.1050900@jp.fujitsu.com>
On Wed, Sep 28, 2011 at 11:21:58AM +0900, KOSAKI Motohiro wrote:
> (2011/09/28 10:45), Minchan Kim wrote:
> > When racing between putback_lru_page and shmem_unlock happens,
> > progrom execution order is as follows, but clear_bit in processor #1
> > could be reordered right before spin_unlock of processor #1.
> > Then, the page would be stranded on the unevictable list.
> >
> > spin_lock
> > SetPageLRU
> > spin_unlock
> > clear_bit(AS_UNEVICTABLE)
> > spin_lock
> > if PageLRU()
> > if !test_bit(AS_UNEVICTABLE)
> > move evictable list
> > smp_mb
> > if !test_bit(AS_UNEVICTABLE)
> > move evictable list
> > spin_unlock
> >
> > But, pagevec_lookup in scan_mapping_unevictable_pages has rcu_read_[un]lock so
> > it could protect reordering before reaching test_bit(AS_UNEVICTABLE) on processor #1
> > so this problem never happens. But it's a unexpected side effect and we should
> > solve this problem properly.
>
> Do we still need this after Hannes removes scan_mapping_unevictable_pages?
Hi KOSAKI,
What Hannes removes is scan_zone_unevictable_pages not scan_mapping_unevictable_pages.
--
Kinds regards,
Minchan Kim
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next prev parent reply other threads:[~2011-09-28 2:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-28 1:45 Minchan Kim
2011-09-28 2:21 ` KOSAKI Motohiro
2011-09-28 2:25 ` Minchan Kim [this message]
2011-09-28 2:48 ` KOSAKI Motohiro
2011-09-28 8:14 ` Johannes Weiner
2011-09-28 18:03 ` Minchan Kim
2011-09-29 9:54 ` [PATCH v2] " Minchan Kim
2011-09-29 12:50 ` KOSAKI Motohiro
2011-09-28 15:04 ` [PATCH] " Lin Ming
2011-09-28 18:05 ` Minchan Kim
2011-09-29 1:02 ` Lin Ming
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