linux-kernel - 2.6.20-rc2+: CFQ halving disk throughput.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 01 Jan 2007 23:46:58 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	Tejun Heo <htejun@...il.com>, Jens Axboe <axboe@...e.de>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...l.org>
Subject: 2.6.20-rc2+: CFQ halving disk throughput.

Tejun Heo wrote:

> Everything seems fine in the dmesg.  Performance degradation is
> probably some other issue in -rc kernel.  I'm suspecting recently
> fixed block layer bug.  If it's still the same in the next -rc,
> please report.

In fact, it's CFQ. The PATA thing was a red herring. 2.6.20-rc2 and 3 
give me ~ 24 MB/s from "hdparm t /dev/hda" while 2.6.20-rc1 and below 
give me ~ 50 MB/s.

Jens: this is due to "[PATCH] cfq-iosched: tighten allow merge 
criteria", 719d34027e1a186e46a3952e8a24bf91ecc33837:

http://www2.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=719d34027e1a186e46a3952e8a24bf91ecc33837

If I revert that one, I have my 50 M/s back. config and dmesg attached 
in case they're useful.

Rene

View attachment "config-2.6.20-rc3" of type "text/plain" (43665 bytes)

View attachment "dmesg-2.6.20-rc3" of type "text/plain" (11435 bytes)