From: Amit Shah <amit.shah@redhat.com>
To: Zhang Haoyu <zhanghy@sangfor.com>
Cc: qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>
Subject: Re: [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial
Date: Fri, 29 Aug 2014 20:08:49 +0530 [thread overview]
Message-ID: <20140829143849.GA8909@grmbl.mre> (raw)
In-Reply-To: <201408291545282753855@sangfor.com>
On (Fri) 29 Aug 2014 [15:45:30], Zhang Haoyu wrote:
> Hi, all
>
> I start a VM with virtio-serial (default ports number: 31), and found that virtio-blk performance degradation happened, about 25%, this problem can be reproduced 100%.
> without virtio-serial:
> 4k-read-random 1186 IOPS
> with virtio-serial:
> 4k-read-random 871 IOPS
>
> but if use max_ports=2 option to limit the max number of virio-serial ports, then the IO performance degradation is not so serious, about 5%.
>
> And, ide performance degradation does not happen with virtio-serial.
Pretty sure it's related to MSI vectors in use. It's possible that
the virtio-serial device takes up all the avl vectors in the guests,
leaving old-style irqs for the virtio-blk device.
If you restrict the number of vectors the virtio-serial device gets
(using the -device virtio-serial-pci,vectors= param), does that make
things better for you?
Amit
next prev parent reply other threads:[~2014-08-29 14:39 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-29 7:45 [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial Zhang Haoyu
2014-08-29 14:38 ` Amit Shah [this message]
2014-09-01 12:38 ` [Qemu-devel] [question] virtio-blk performance degradationhappened " Zhang Haoyu
2014-09-01 12:46 ` Amit Shah
2014-09-01 12:57 ` [Qemu-devel] [question] virtio-blk performancedegradationhappened " Zhang Haoyu
2014-09-01 12:52 ` [Qemu-devel] [question] virtio-blk performance degradationhappened " Zhang Haoyu
2014-09-01 13:09 ` Christian Borntraeger
2014-09-01 13:12 ` Paolo Bonzini
2014-09-01 13:22 ` Christian Borntraeger
2014-09-01 13:29 ` Paolo Bonzini
2014-09-01 14:03 ` Christian Borntraeger
2014-09-01 14:15 ` Christian Borntraeger
2014-09-04 7:56 ` [Qemu-devel] [question] virtio-blk performance degradationhappenedwith virito-serial Zhang Haoyu
2014-09-07 9:46 ` Zhang Haoyu
2014-09-11 6:11 ` Amit Shah
2014-09-12 3:21 ` [Qemu-devel] [question] virtio-blk performance degradation happened with virito-serial Zhang Haoyu
2014-09-12 12:38 ` Stefan Hajnoczi
2014-09-13 17:22 ` Max Reitz
2014-09-16 14:59 ` Zhang Haoyu
2014-09-02 6:36 ` [Qemu-devel] [question] virtio-blk performance degradationhappened " Amit Shah
2014-09-02 18:05 ` Andrey Korolyov
2014-09-02 18:11 ` Amit Shah
2014-09-02 18:27 ` Andrey Korolyov
2014-09-04 2:20 ` [Qemu-devel] [question] virtio-blk performancedegradationhappened " Zhang Haoyu
2014-09-19 5:53 ` [Qemu-devel] [question] virtio-blk performance degradationhappened " Fam Zheng
2014-09-19 13:35 ` Paolo Bonzini
2014-09-22 13:23 ` [Qemu-devel] [question] virtio-blk performancedegradationhappened " Zhang Haoyu
2014-09-23 1:29 ` Fam Zheng
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