Package: linux-image-2.6.32-5-686
Version: 2.6.32-35squeeze2jba
Severity: normal


After adding a ssd (OCZ Vertex Plus 60GB) to my squeeze system (debian kernel 2.6.32)
I was disappointed about its performance, as it was advertised with 185 MB/s.

/dev/sdb:
Timing buffered disk reads: 214 MB in 3.01 seconds = 71.04 MB/sec

However, when running recent knoppix (kernel 3.0.4) I got the expected performance:

/dev/sdb:
Timing buffered disk reads: 490 MB in 3.00 seconds = 163.07 MB/sec

After googling, I found that this has been reported before:

http://www.archivum.info/linux-ide@vger.kernel.org/2010-02/00243/bad-performance-with-SSD-since-kernel-version-2.6.32.html

It seems that early versions of kernel 2.6.32 have a bug that results in bad performance of some
ssds (maybe all, at least the 'OCZ Vertex Plus 60GB' and the 'Super Talent Ultradrive GX MLC 64GB').
Reverting the patch as described in the discussion solved the problem for me. I now have the
desired performance.

Thus, I would suggest to revert the patch "block: improve queue_should_plug() by looking at
IO depths" in kernel 2.6.32 for squeeze in order to get full ssd performance. I think the bugfix
is important as an increasing number of users havs ssds and the bug more or less breaks ssd
performance in squeeze.

Juergen



-- System Information:
Debian Release: 6.0.2
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-5-686 (SMP w/2 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages linux-image-2.6.32-5-686 depends on:
ii coreutils 8.5-1 GNU core utilities
ii debconf [debconf-2.0] 1.5.36.1 Debian configuration management sy

linux-image-2.6.32-5-686 recommends no packages.

Versions of packages linux-image-2.6.32-5-686 suggests:
pn fdutils <none> (no description available)
pn ksymoops <none> (no description available)
pn linux-doc-2.6.32-5-686 | linu <none> (no description available)
pn linux-image-2.6.32-5-686-dbg <none> (no description available)

-- debconf information:
linux-image-2.6.32-5-686/preinst/failed-to-move-modules-2.6.32-5-686:
linux-image-2.6.32-5-686/postinst/kimage-is-a-directory:
linux-image-2.6.32-5-686/postinst/depmod-error-initrd-2.6.32-5-686: false
linux-image-2.6.32-5-686/postinst/ignoring-do-bootloader-2.6.32-5-686:
linux-image-2.6.32-5-686/postinst/old-system-map-link-2.6.32-5-686: true
linux-image-2.6.32-5-686/postinst/missing-firmware-2.6.32-5-686:
* linux-image-2.6.32-5-686/preinst/overwriting-modules-2.6.32-5-686: false
linux-image-2.6.32-5-686/prerm/removing-running-kernel-2.6.32-5-686: true
linux-image-2.6.32-5-686/postinst/depmod-error-2.6.32-5-686: false
linux-image-2.6.32-5-686/postinst/old-dir-initrd-link-2.6.32-5-686: true
linux-image-2.6.32-5-686/preinst/abort-overwrite-2.6.32-5-686:
* linux-image-2.6.32-5-686/preinst/already-running-this-2.6.32-5-686:



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Sorry, I dont want to bother. But there has been no comment in one month. Does this
mean that the kernel team is just too busy or does it mean that I posted in the wrong place?

Juergen
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On Mon, 2011-10-24 at 21:04 +0200, Juergen Bausa wrote:
> Sorry, I dont want to bother. But there has been no comment in one month. Does this
> mean that the kernel team is just too busy or does it mean that I posted in the wrong place?

This is the right place, but we're busy.

Ben.

--
Ben Hutchings
Reality is just a crutch for people who can't handle science fiction.