From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
Kashyap Desai <kashyap.desai@broadcom.com>,
Laurence Oberman <loberman@redhat.com>,
Omar Sandoval <osandov@fb.com>, Christoph Hellwig <hch@lst.de>,
Bart Van Assche <bart.vanassche@wdc.com>
Subject: Re: [PATCH V2 2/3] blk-mq: only attempt to merge bio if there is rq in sw queue
Date: Fri, 29 Jun 2018 10:35:02 +0200 [thread overview]
Message-ID: <20180629083502.GD15870@lst.de> (raw)
In-Reply-To: <20180629081252.13836-3-ming.lei@redhat.com>
On Fri, Jun 29, 2018 at 04:12:51PM +0800, Ming Lei wrote:
> Only attempt to merge bio iff the ctx->rq_list isn't empty, because:
>
> 1) for high-performance SSD, most of times dispatch may succeed, then
> there may be nothing left in ctx->rq_list, so don't try to merge over
> sw queue if it is empty, then we can save one acquiring of ctx->lock
>
> 2) we can't expect good merge performance on per-cpu sw queue, and missing
> one merge on sw queue won't be a big deal since tasks can be scheduled from
> one CPU to another.
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
next prev parent reply other threads:[~2018-06-29 8:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-29 8:12 [PATCH V2 0/3] blk-mq: improve IO perf in case of none io sched Ming Lei
2018-06-29 8:12 ` [PATCH V2 1/3] blk-mq: use list_splice_tail_init() to insert requests Ming Lei
2018-06-29 8:34 ` Christoph Hellwig
2018-06-29 8:12 ` [PATCH V2 2/3] blk-mq: only attempt to merge bio if there is rq in sw queue Ming Lei
2018-06-29 8:35 ` Christoph Hellwig [this message]
2018-06-29 8:12 ` [PATCH V2 3/3] blk-mq: dequeue request one by one from sw queue iff hctx is busy Ming Lei
2018-06-29 8:39 ` Christoph Hellwig
2018-06-29 15:24 ` Ming Lei
2018-06-29 14:58 ` Jens Axboe
2018-06-29 15:34 ` Ming Lei
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