Messages in this thread | | | From | "Miquel van Smoorenburg" <> | Subject | Re: IO scheduler, queue depth, nr_requests | Date | Wed, 25 Feb 2004 21:39:23 +0000 (UTC) |
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In article <403D02E3.4070208@tmr.com>, Bill Davidsen <davidsen@tmr.com> wrote: >linux.kernelNick Piggin wrote: > >> But the whole reason it is getting blocked in the first place >> is because your controller is sucking up all your requests. >> The whole problem is not a problem if you use properly sized >> queues. >> >> I'm a bit surprised that it wasn't working well with a controller >> queue depth of 64 and 128 nr_requests. I'll give you a per process >> request limit patch to try in a minute. > >And there's the rub... he did try what you are calling correctly sized >queues, and his patch works better. I'm all in favor of having the >theory and then writing the code, but when something works I would >rather understand why and modify the theory.
Ah, but we now do understand why - it was pdflush and a process fighting over get_request on basically the same device, before and after LVM remapping.
See:
http://www.ussg.iu.edu/hypermail/linux/kernel/0402.2/1522.html
More complete solutions:
https://www.redhat.com/archives/linux-lvm/2004-February/msg00203.html https://www.redhat.com/archives/linux-lvm/2004-February/msg00215.html
Mike.
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