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Message-ID: <874mv7cnml.fsf@rustcorp.com.au> Date: Tue, 14 Oct 2014 14:24:10 +1030 From: Rusty Russell <rusty@...tcorp.com.au> To: Ming Lei <ming.lei@...onical.com> Cc: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@...radead.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Kick In <pierre-andre.morey@...onical.com>, Chris J Arges <chris.j.arges@...onical.com> Subject: Re: [PATCH] blk-merge: fix blk_recount_segments Ming Lei <ming.lei@...onical.com> writes: > Hi Rusty, Hi Ming! Sorry, I was on vacation. I'm back and slowly working through all my mail... > 1, FIO script > [global] > direct=1 > size=128G > bsrange=${BS}-${BS} > timeout=60 > numjobs=4 > ioengine=libaio > iodepth=64 > filename=/dev/vdb #backed by /dev/nullb0, 4 virtqueues per virtio-blk > group_reporting=1 > > [f] > rw=randread > 5, result > 5.1 without Rusty's virtio-vring patch > - BS=4K, throughput: 179K > - BS=256K, throughput: 27540 (ie. always using indirect) > 5.2 with Rusty's virtio-vring patch > - BS=4K, throughput: 173K > - BS=256K, throughput: 25350 (ie. usually using indirect). > Looks throughput decreases if BS is 256K in case of your patch. Interesting. Looks like we're ending up with fewer descs in flight, though I'm surprised: with 256K blocks I'd expect us to hit the steady state of "all indirect" almost immediately. Hmm... I think the heuristic in my patch is flawed. Let me try again, and get back to you. Thanks, Rusty. -- 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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