From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Rik van Riel <riel@redhat.com>, Michal Hocko <mhocko@suse.cz>,
Kent Overstreet <kent.overstreet@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: vmscan: Stop reclaim/compaction earlier due to insufficient progress if !__GFP_REPEAT
Date: Thu, 17 Feb 2011 14:22:09 -0800 [thread overview]
Message-ID: <20110217142209.8736cca1.akpm@linux-foundation.org> (raw)
In-Reply-To: <20110216095048.GA4473@csn.ul.ie>
On Wed, 16 Feb 2011 09:50:49 +0000
Mel Gorman <mel@csn.ul.ie> wrote:
> should_continue_reclaim() for reclaim/compaction allows scanning to continue
> even if pages are not being reclaimed until the full list is scanned. In
> terms of allocation success, this makes sense but potentially it introduces
> unwanted latency for high-order allocations such as transparent hugepages
> and network jumbo frames that would prefer to fail the allocation attempt
> and fallback to order-0 pages. Worse, there is a potential that the full
> LRU scan will clear all the young bits, distort page aging information and
> potentially push pages into swap that would have otherwise remained resident.
afaict the patch affects order-0 allocations as well. What are the
implications of this?
Also, what might be the downsides of this change, and did you test for
them?
> This patch will stop reclaim/compaction if no pages were reclaimed in the
> last SWAP_CLUSTER_MAX pages that were considered.
a) Why SWAP_CLUSTER_MAX? Is (SWAP_CLUSTER_MAX+7) better or worse?
b) The sentence doesn't seem even vaguely accurate. shrink_zone()
will scan vastly more than SWAP_CLUSTER_MAX pages before calling
should_continue_reclaim(). Confused.
c) The patch doesn't "stop reclaim/compaction" fully. It stops it
against one zone. reclaim will then advance on to any other
eligible zones.
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next prev parent reply other threads:[~2011-02-17 22:22 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-09 15:46 [patch] vmscan: fix zone shrinking exit when scan work is done Johannes Weiner
2011-02-09 15:54 ` Kent Overstreet
2011-02-09 16:46 ` Mel Gorman
2011-02-09 18:28 ` Andrea Arcangeli
2011-02-09 20:05 ` Andrew Morton
2011-02-10 10:21 ` Mel Gorman
2011-02-10 10:41 ` Michal Hocko
2011-02-10 12:48 ` Andrea Arcangeli
2011-02-10 13:33 ` Mel Gorman
2011-02-10 14:14 ` Andrea Arcangeli
2011-02-10 14:58 ` Mel Gorman
2011-02-16 9:50 ` [PATCH] mm: vmscan: Stop reclaim/compaction earlier due to insufficient progress if !__GFP_REPEAT Mel Gorman
2011-02-16 10:13 ` Andrea Arcangeli
2011-02-16 11:22 ` Mel Gorman
2011-02-16 14:44 ` Andrea Arcangeli
2011-02-16 12:03 ` Andrea Arcangeli
2011-02-16 12:14 ` Rik van Riel
2011-02-16 12:38 ` Johannes Weiner
2011-02-16 23:26 ` Minchan Kim
2011-02-17 22:22 ` Andrew Morton [this message]
2011-02-18 12:22 ` Mel Gorman
2011-02-10 4:04 ` [patch] vmscan: fix zone shrinking exit when scan work is done Minchan Kim
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