Re: [BUG] BUG_ON in I/O scheduler, bugme # 288

[Nick Piggin <piggin@cyberone.com.au>]

Dave Olien 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
>
>I've also put a more complete report in my web site:
>
>	http://www.osdl.org/archive/dmo/deadline_bugon.
>
>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.
>
Thanks for the report. Andrew, I think this may be because
deadline_add_drq_rb puts "aliased" requests in the next_drq although they
are not put on the sort or fifo lists. This is the problem I described to
you before and exists in mm4.

Nick