linux-kernel - Re: [PATCH] mm/readahead.c: update the LRU positions of in-core pages, too

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Message-ID: <20100126133217.GB25407@localhost>
Date:	Tue, 26 Jan 2010 21:32:17 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Chris Frost <frost@...ucla.edu>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steve Dickson <steved@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Xu Chenfeng <xcf@...c.edu.cn>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Steve VanDeBogart <vandebo-lkml@...dbox.net>
Subject: Re: [PATCH] mm/readahead.c: update the LRU positions of in-core
	pages, too

On Mon, Jan 25, 2010 at 03:36:35PM -0700, Chris Frost wrote:
> I changed Wu's patch to add a PageLRU() guard that I believe is required
> and optimized zone lock acquisition to only unlock and lock at zone changes.
> This optimization seems to provide a 10-20% system time improvement for
> some of my GIMP benchmarks and no improvement for other benchmarks.

> +			del_page_from_lru_list(zone, page, lru);
> +			add_page_to_lru_list(zone, page, lru);
> +		}
> +		put_page(page);

Hmm. put_page() inside lru_lock can deadlock. So you need to further
optimize the code to do pagevec_lookup() and pagevec_release() plus
cond_resched().

Thanks,
Fengguang
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