linux-kernel - Performance regression in IO scheduler still there

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Date:	Mon, 26 Oct 2009 18:20:12 +0100
From:	Jan Kara <jack@...e.cz>
To:	jens.axboe@...cle.com
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Jeff Moyer <jmoyer@...hat.com>,
	Chris Mason <chris.mason@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>
Subject: Performance regression in IO scheduler still there

  Hi,

  I took time and remeasured tiobench results on recent kernel. A short
conclusion is that there is still a performance regression which I reported
few months ago. The machine is Intel 2 CPU with 2 GB RAM and plain SATA
drive. tiobench sequential write performance numbers with 16 threads:
2.6.29:              AVG       STDERR
37.80 38.54 39.48 -> 38.606667 0.687475

2.6.32-rc5:
37.36 36.41 36.61 -> 36.793333 0.408928 

So about 5% regression. The regression happened sometime between 2.6.29 and
2.6.30 and stays the same since then... With deadline scheduler, there's
no regression. Shouldn't we do something about it?

								Honza
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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