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Message-ID: <20110613214154.GL633@redhat.com> Date: Mon, 13 Jun 2011 17:41:54 -0400 From: Vivek Goyal <vgoyal@...hat.com> To: Tao Ma <tm@....ma> Cc: linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk> Subject: Re: CFQ: async queue blocks the whole system On Mon, Jun 13, 2011 at 06:08:40PM +0800, Tao Ma wrote: [..] > > You can also run iostat on disk and should be able to see that with > > the patch you are dispatching writes more often than before. > Sorry, the patch doesn't work. > > I used trace event to capture all the blktraces since it doesn't > interfere with the tests, hope it helps. Actually I was looking for CFQ traces. This seems to be generic block layer trace points. May be you can use "blktrace -d /dev/<device>" and then blkparse. It also gives the aggregate view which is helpful. > > Please downloaded it from http://blog.coly.li/tmp/blktrace.tar.bz2 What concerns me is following. 5255.521353: block_rq_issue: 8,0 W 0 () 571137153 + 8 [attr_set] 5578.863871: block_rq_issue: 8,0 W 0 () 512950473 + 48 [kworker/0:1] IIUC, we dispatched second write more than 300 seconds after dispatching 1 write. What happened in between. We should have dispatched more writes. CFQ traces might give better idea in terms of whether wl_type for async queues was scheduled or not at all. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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