From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: compaction: Do not accidentally skip pageblocks in the migrate scanner
Date: Thu, 20 Dec 2012 17:45:50 -0500 [thread overview]
Message-ID: <50D3951E.50107@redhat.com> (raw)
In-Reply-To: <20121220142232.GA13367@suse.de>
On 12/20/2012 09:22 AM, Mel Gorman wrote:
> Compaction uses the ALIGN macro incorrectly with the migrate scanner by
> adding pageblock_nr_pages to a PFN. It happened to work when initially
> implemented as the starting PFN was also aligned but with caching restarts
> and isolating in smaller chunks this is no longer always true. The impact is
> that the migrate scanner scans outside its current pageblock. As pfn_valid()
> is still checked properly it does not cause any failure and the impact
> of the bug is that in some cases it will scan more than necessary when
> it crosses a page boundary but by no more than COMPACT_CLUSTER_MAX. It
> is highly unlikely this is even measurable but it's still wrong so this
> patch addresses the problem.
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: compaction: Do not accidentally skip pageblocks in the migrate scanner
Date: Thu, 20 Dec 2012 17:45:50 -0500 [thread overview]
Message-ID: <50D3951E.50107@redhat.com> (raw)
In-Reply-To: <20121220142232.GA13367@suse.de>
On 12/20/2012 09:22 AM, Mel Gorman wrote:
> Compaction uses the ALIGN macro incorrectly with the migrate scanner by
> adding pageblock_nr_pages to a PFN. It happened to work when initially
> implemented as the starting PFN was also aligned but with caching restarts
> and isolating in smaller chunks this is no longer always true. The impact is
> that the migrate scanner scans outside its current pageblock. As pfn_valid()
> is still checked properly it does not cause any failure and the impact
> of the bug is that in some cases it will scan more than necessary when
> it crosses a page boundary but by no more than COMPACT_CLUSTER_MAX. It
> is highly unlikely this is even measurable but it's still wrong so this
> patch addresses the problem.
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
next prev parent reply other threads:[~2012-12-20 22:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-20 14:22 [PATCH] mm: compaction: Do not accidentally skip pageblocks in the migrate scanner Mel Gorman
2012-12-20 14:22 ` Mel Gorman
2012-12-20 22:45 ` Rik van Riel [this message]
2012-12-20 22:45 ` Rik van Riel
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