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SubjectRe: Blocked processes <=> Elevator starvation?
On Fri, 27 Oct 2000, Jens Axboe wrote:

...
> > So it seems the process is either in a loop in ___wait_on_page()
> > racing for the PageLock or it never wakes-up... (I guess I could add a
> > printk to check which)
> > Unfortunately I didn't find anything obviously wrong with the code.
> > I hope you can do a better job tracking the problem down.
>
> Rik is right, just because you are seeing long waits on wait_on_page
> doesn't make it a vm problem. When a I/O on a page completes, the
> page will be unlocked and wait_on_page can grab it -- so I/O stalls
> would results in this behaviour.
>
> Could you try this patch:
>
> *.kernel.org/pub/linux/kernel/people/axboe/patches/2.4.0-test10-pre6/blk-7.bz2
>
> and see if it makes a difference?

After adding

#define ELEVATOR_HOLE_MERGE 3

to linux/include/linux/elevator.h it compiled ok.
There were still some stalls but they only lasted a couple of
seconds. The patch did make a difference and for the better.

Rui Sousa

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