Comment 34 for bug 620074
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#34 |
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0e1f616
(Get the code!)
>
> Fwiw, I've never used the CFQ scheduler. I'm on the deadline scheduler with
> my
> 3ware 9560SE and still see this problem crop up from time to time, usually
> when
> doing a file copy large enough to fill the page cache.
>
Another deadliner here. And the same thing. There are two clear cut triggers for me:
1. The test case thomas posted.
2. large copies which fill up page cache.
I think its a process scheduling bug because page cache fill up might be triggering the pdflush processes (which are btw, normal priority. why?) into hyper drive and causing all other processes to wait. We do see various processes going into 'D' state and pdflush at the top of the cpu usage list, when the symptoms occur.
If CFQ is used, and process priority determines IO priority, aren't pdflush processes going to compete with processes doing their own IO when dirty_ratio is reached and the process has priority equal or better than 0 (-1 and higher)? That may explain some of the stories with CFQ here.