Messages in this thread | | | Date | Fri, 5 Aug 2011 14:26:33 -0700 | Subject | Re: [PATCH] block: Make rq_affinity = 1 work as expected. | From | "Williams, Dan J" <> |
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On Thu, Aug 4, 2011 at 10:12 PM, Shaohua Li <shli@kernel.org> wrote: > 2011/8/5 Tao Ma <tm@tao.ma>: >> From: Tao Ma <boyu.mt@taobao.com> >> >> Commit 5757a6d76c introduced a new rq_affinity = 2 so as to make >> the request completed in the __make_request cpu. But it makes the >> old rq_affinity = 1 not work any more. The root cause is that >> if the 'cpu' and 'req->cpu' is in the same group and cpu != req->cpu, >> ccpu will be the same as group_cpu, so the completion will be >> excuted in the 'cpu' not 'group_cpu'. >> >> This patch fix problem by simpling removing group_cpu and the codes >> are more explicit now. If ccpu == cpu, we complete in cpu, otherwise >> we raise_blk_irq to ccpu. > good catch. This changed old behavior and can cause more lock contention. > and if user doesn't care about lock contention, he can use rq_affinity = 2 >
Indeed it does change behavior of rq_affinity=1, apologies.
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
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