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Date: Sat, 16 Nov 2002 19:46:22 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Marc-Christian Petersen <m.c.p@wolk-project.de>
Cc: linux-kernel@vger.kernel.org, Con Kolivas <conman@kolivas.net>
Subject: Re: 2.[45] fixes for design locking bug in wait_on_page/wait_on_buffer/get_request_wait
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On Sat, Nov 16, 2002 at 06:43:36PM +0100, Marc-Christian Petersen wrote:
> On Saturday 16 November 2002 18:32, Andrea Arcangeli wrote:
> 
> Hi Andrea,
> 
> > you may want to try with this setting that helps with very slow devices:
> > 	echo 2 500 0 0 500 3000 3 1 0 > /proc/sys/vm/bdflush
> >
> > or also with my current default tuned for high performance:
> > 	echo 50 500 0 0 500 3000 60 20 > /proc/sys/vm/bdflush
> I've tested both without any changes, "pausings" are still there.
> 
> > you may have too many dirty buffers around and you end running at disk
> > speed at every memory allocation, the first setting will decrease the
> > amount of dirty buffers dramatically, if you still have significant
> > slowdown with the first setting above, it's most probably only the usual
> > elevator issue.
> Seems so.
> 
> So I have to use 2.4.18 until there is a real proper fix for that.

just to make a quick test, can you try an hack like this combined with a
setting of elvtune -r 128 -w 256 on top of 2.4.20rc1?

--- x/drivers/block/ll_rw_blk.c.~1~	Sat Nov  2 19:45:33 2002
+++ x/drivers/block/ll_rw_blk.c	Sat Nov 16 19:44:20 2002
@@ -432,7 +432,7 @@ static void blk_init_free_list(request_q
 
 	si_meminfo(&si);
 	megs = si.totalram >> (20 - PAGE_SHIFT);
-	nr_requests = 128;
+	nr_requests = 16;
 	if (megs < 32)
 		nr_requests /= 2;
 	blk_grow_request_list(q, nr_requests);



Andrea
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