linux-kernel - Re: [PATCH 08/12] vmscan: Setup pagevec as late as possible in shrink_inactive

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Message-Id: <20100616164309.254b1a0d.akpm@linux-foundation.org>
Date:	Wed, 16 Jun 2010 16:43:09 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 08/12] vmscan: Setup pagevec as late as possible in
 shrink_inactive_list()

On Mon, 14 Jun 2010 12:17:49 +0100
Mel Gorman <mel@....ul.ie> wrote:

> shrink_inactive_list() sets up a pagevec to release unfreeable pages. It
> uses significant amounts of stack doing this. This patch splits
> shrink_inactive_list() to take the stack usage out of the main path so
> that callers to writepage() do not contain an unused pagevec on the
> stack.

You can get the entire pagevec off the stack - just make it a
static-to-shrink_inactive_list() pagevec-per-cpu.

Locking just requires pinning to a CPU.  We could trivially co-opt
shrink_inactive_list()'s spin_lock_irq() for that, but
pagevec_release() can be relatively expensive so it'd be sad to move
that inside spin_lock_irq().  It'd be better to slap a
get_cpu()/put_cpu() around the whole thing.

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