Messages in this thread | | | Date | Sun, 11 Sep 2011 11:51:28 +0900 | From | Tejun Heo <> | Subject | Re: [RFC]block: don't mark flush request as SOFTBARRIER |
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Hello,
On Thu, Sep 08, 2011 at 09:29:54AM +0800, Shaohua Li wrote: > I'm wondering why flush request should be marked as > SOFTBARRIER. Current flush sequence guarantees the correctness of > flush even the request is reordered by ioscheduler.
The primary reason would be because when those flush data requests are put on the dispatch queue, it doesn't go through elv_dispatch_sort(). SOFTBARRIERs function as dispatch sort boundaries and queueing flush data request at the head w/o SOFTBARRIER would confuse dispatch sorting, and we want to put it at the head of dispatch queue to decrease latency for flush sequence.
Thanks.
-- tejun
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