From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Mon, 30 Aug 2004 15:37:30 -0700
From: Andrew Morton <akpm@osdl.org>
Subject: Re: Kernel 2.6.8.1: swap storm of death - nr_requests > 1024 on
 swap partition
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To: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Cc: karl.vogel@pandora.be, axboe@suse.de, wli@holomorphy.com, linux-mm@kvack.org
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Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
>
>  static int may_write_to_queue(struct backing_dev_info *bdi)
>  {
> +	int nr_writeback = read_page_state(nr_writeback);
> +
> +	if (nr_writeback > (totalram_pages * 25 / 100)) { 
> +		blk_congestion_wait(WRITE, HZ/5);
> +		return 0;
> +	}

That's probably a good way of special-casing this special-place problem.

For a final patch I'd be inclined to take into account /proc/sys/vm/dirty_ratio
and to avoid running the expensive read_page_state() once per writepage.
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