From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@fb.com>,
linux-block@vger.kernel.org, Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, Bart Van Assche <bart.vanassche@sandisk.com>,
Laurence Oberman <loberman@redhat.com>,
Paolo Valente <paolo.valente@linaro.org>,
Oleksandr Natalenko <oleksandr@natalenko.name>,
Tom Nguyen <tom81094@gmail.com>,
linux-kernel@vger.kernel.org, Omar Sandoval <osandov@fb.com>
Subject: Re: [PATCH V5 8/8] blk-mq: improve bio merge from blk-mq sw queue
Date: Mon, 9 Oct 2017 12:28:37 +0800 [thread overview]
Message-ID: <20171009042835.GA19029@ming.t460p> (raw)
In-Reply-To: <20171003092143.GF2771@infradead.org>
On Tue, Oct 03, 2017 at 02:21:43AM -0700, Christoph Hellwig wrote:
> This looks generally good to me, but I really worry about the impact
> on very high iops devices. Did you try this e.g. for random reads
> from unallocated blocks on an enterprise NVMe SSD?
Looks no such impact, please see the following data
in the fio test(libaio, direct, bs=4k, 64jobs, randread, none scheduler)
[root@storageqe-62 results]# ../parse_fio 4.14.0-rc2.no_blk_mq_perf+-nvme-64jobs-mq-none.log 4.14.0-rc2.BLK_MQ_PERF_V5+-nvme-64jobs-mq-none.log
---------------------------------------
IOPS(K) | NONE | NONE
---------------------------------------
randread | 650.98 | 653.15
---------------------------------------
OR:
If you worry about this impact, can we simply disable merge on NVMe
for none scheduler? It is basically impossible to merge NVMe's
request/bio when none is used, but it can be doable in case of kyber
scheduler.
--
Ming
prev parent reply other threads:[~2017-10-09 4:28 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-30 11:26 [PATCH V5 0/8] blk-mq: improve bio merge for none scheduler Ming Lei
2017-09-30 11:26 ` [PATCH V5 1/8] blk-mq-sched: introduce blk_mq_sched_queue_depth() Ming Lei
2017-09-30 11:26 ` [PATCH V5 2/8] blk-mq-sched: use q->queue_depth as hint for q->nr_requests Ming Lei
2017-09-30 11:26 ` [PATCH V5 3/8] block: introduce rqhash helpers Ming Lei
2017-10-03 9:15 ` Christoph Hellwig
2017-09-30 11:26 ` [PATCH V5 4/8] block: move actual bio merge code into __elv_merge Ming Lei
2017-10-03 9:16 ` Christoph Hellwig
2017-09-30 11:26 ` [PATCH V5 5/8] block: add check on elevator for supporting bio merge via hashtable from blk-mq sw queue Ming Lei
2017-10-03 9:17 ` Christoph Hellwig
2017-09-30 11:26 ` [PATCH V5 6/8] block: introduce .last_merge and .hash to blk_mq_ctx Ming Lei
2017-10-03 9:19 ` Christoph Hellwig
2017-09-30 11:26 ` [PATCH V5 7/8] blk-mq-sched: refactor blk_mq_sched_try_merge() Ming Lei
2017-10-03 9:20 ` Christoph Hellwig
2017-09-30 11:26 ` [PATCH V5 8/8] blk-mq: improve bio merge from blk-mq sw queue Ming Lei
2017-10-03 9:21 ` Christoph Hellwig
2017-10-09 4:28 ` Ming Lei [this message]
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