linux-kernel - Re: virtio-scsi <-> vhost multi lun/adapter performance results with 3.6-rc0

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Message-ID: <CAJSP0QXX=4etJ_uGYFzXQ0eEE0M+Ude7ha0aH5SaX1oEUvQoLA@mail.gmail.com>
Date:	Sat, 11 Aug 2012 13:52:04 +0100
From:	Stefan Hajnoczi <stefanha@...il.com>
To:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
Cc:	target-devel <target-devel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>,
	kvm-devel <kvm@...r.kernel.org>,
	lf-virt <virtualization@...ts.linux-foundation.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Christoph Hellwig <hch@....de>, hare@...e.de,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <jaxboe@...ionio.com>
Subject: Re: virtio-scsi <-> vhost multi lun/adapter performance results with 3.6-rc0

On Sat, Aug 11, 2012 at 12:23 AM, Nicholas A. Bellinger
<nab@...ux-iscsi.org> wrote:
> Using a KVM guest with 32x vCPUs and 4G memory, the results for 4x
> random I/O now look like:
>
> workload         | jobs | 25% write / 75% read | 75% write / 25% read
> -----------------|------|----------------------|---------------------
> 1x rd_mcp LUN    |   8  |     ~155K IOPs       |      ~145K IOPs
> 16x rd_mcp LUNs  |  16  |     ~315K IOPs       |      ~305K IOPs
> 32x rd_mcp LUNs  |  16  |     ~425K IOPs       |      ~410K IOPs
>
> The full fio randrw results for the six test cases are attached below.
> Also, using a workload of fio numjobs > 16 currently makes performance
> start to fall off pretty sharply regardless of the number of vCPUs..
>
> So running a similar workload with loopback SCSI ports on bare-metal
> produces ~1M random IOPs with 12x LUNs + numjobs=32.  At numjobs=16 here
> with vhost the 16x LUN configuration ends up being in the range of ~310K
> IOPs for the current sweet spot..

This makes me wonder what a comparison against baremetal looks like
and the perf top, mpstat, and kvm_stat results on the host.

Stefan
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