Messages in this thread | | | Date | Thu, 23 Jan 2003 14:38:24 -0800 | From | Andrew Morton <> | Subject | Re: [BUG] BUG_ON in I/O scheduler, bugme # 288 |
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Dave Olien <dmo@osdl.org> wrote: > > > Jens, Andrew > > The group here doing dbt2 workload measurements have hit a couple of > problems APPARENTLY in the block I/O scheduler when doing write-intensive > raw disk I/O through a DAC960 extremeraid 2000 controller. > This wasn't a problem in 2.5.49. It has appeared since then. > > I've filed a bug on the OSDL bugme database. You can read it at: > > http://bugme.osdl.org/show_bug.cgi?id=288
The title is "2.5.59 and 2.5.50-mm2". I assume it should be 2.5.59-mm2??
> I've also put a more complete report in my web site: > > http://www.osdl.org/archive/dmo/deadline_bugon.
oooh, goody. A new stresstest tool.
> Begin with the README file. > > For same reason, the README file isn't appearing on my web page. > I'll look into that. In the mean time, I've included the contests > of the README file below. > > I'm about to try reproducing the problem on a smaller hardware > configuration. Then, I'll test whether the same problem occurs with > read intensive I/O.
OK, thanks.
The important thing about direct-io is that it will frequently cause multiple I/Os to be in flight against the same disk sector. That will never happen with regular I/O because the pagecache acts as a synchronisation point.
Probably, this has tickled a bug in the I/O scheduler. Possibly in direct-io, too - that code's fairly fresh, and quite complex.
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