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SubjectRe: [BUG] /proc/<pid>/stat access stalls badly for swapping process, 2.4.0-test10
On Thu, Nov 02 2000, Val Henson wrote:
> > > 3) combine this with the elevator starvation stuff (ask Jens
> > > Axboe for blk-7 to alleviate this issue) and you have a
> > > scenario where processes using /proc/<pid>/stat have the
> > > possibility to block on multiple processes that are in the
> > > process of handling a page fault (but are being starved)
> >
> > I'm experimenting with blk.[67] in test10 right now. The stalls
> > are not helped at all. It doesn't seem to become request bound
> > (haven't instrumented that yet to be sure) but the stalls persist.
> >
> > -Mike
>
> This is not an elevator starvation problem.

True, but the blk-xx patches help work-around (what I believe) is
bad flushing behaviour by the vm.

> I also experienced these stalls with my IDE-only system. Unless I'm
> badly mistaken, the elevator is only used on SCSI disks, therefore
> elevator starvation cannot be blamed for this problem. These stalls
> are particularly annoying since I want to find the pid of the process
> hogging memory in order to kill it, but the read from /proc stalls for
> 45 seconds or more.

You are badly mistaken.

--
* Jens Axboe <axboe@suse.de>
* SuSE Labs
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