Messages in this thread | | | Date | Thu, 17 Sep 2015 16:08:19 -0700 | Subject | Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug() | From | Linus Torvalds <> |
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On Thu, Sep 17, 2015 at 3:42 PM, Chris Mason <clm@fb.com> wrote: > > Playing around with the plug a little, most of the unplugs are coming > from the cond_resched_lock(). Not really sure why we are doing the > cond_resched() there, we should be doing it before we retake the lock > instead. > > This patch takes my box (with dirty thresholds at 1.5GB/3GB) from 195K > files/sec up to 213K. Average IO size is the same as 4.3-rc1.
Ok, so at least for you, part of the problem really ends up being that there's a mix of the "synchronous" unplugging (by the actual explicit "blk_finish_plug(&plug);") and the writeback that is handed off to kblockd_workqueue.
I'm not seeing why that should be an issue. Sure, there's some CPU overhead to context switching, but I don't see that it should be that big of a deal.
I wonder if there is something more serious wrong with the kblockd_workqueue.
Linus
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