From: "Benoît Canet" <benoit.canet@irqsave.net>
To: Chris Friesen <chris.friesen@windriver.com>
Cc: "Benoît Canet" <benoit.canet@irqsave.net>,
"Paolo Bonzini" <pbonzini@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] is there a limit on the number of in-flight I/O operations?
Date: Mon, 21 Jul 2014 17:15:40 +0200 [thread overview]
Message-ID: <20140721151540.GA22161@irqsave.net> (raw)
In-Reply-To: <53CD2AE1.6080803@windriver.com>
The Monday 21 Jul 2014 à 08:59:45 (-0600), Chris Friesen wrote :
> On 07/19/2014 02:45 AM, Benoît Canet wrote:
>
> >I think in the throttling case the number of in flight operation is limited by
> >the emulated hardware queue. Else request would pile up and throttling would be
> >inefective.
> >
> >So this number should be around: #define VIRTIO_PCI_QUEUE_MAX 64 or something like than that.
>
> Okay, that makes sense. Do you know how much data can be written as part of
> a single operation? We're using 2MB hugepages for the guest memory, and we
> saw the qemu RSS numbers jump from 25-30MB during normal operation up to
> 120-180MB when running dbench. I'd like to know what the worst-case would
> be.
I think Linux as a limit of 512Kb for io size or something like that.
So the guest would have VIRTIO_PCI_QUEUE_MAX * 512Kb of in flight buffers at max.
>
> Thanks,
> Chris
next prev parent reply other threads:[~2014-07-21 15:16 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-18 14:58 [Qemu-devel] is there a limit on the number of in-flight I/O operations? Chris Friesen
2014-07-18 15:24 ` Paolo Bonzini
2014-07-18 16:22 ` Chris Friesen
2014-07-18 20:13 ` Paolo Bonzini
2014-07-18 22:48 ` Chris Friesen
2014-07-19 5:49 ` Paolo Bonzini
2014-07-19 6:27 ` Chris Friesen
2014-07-19 7:23 ` Paolo Bonzini
2014-07-19 8:45 ` Benoît Canet
2014-07-21 14:59 ` Chris Friesen
2014-07-21 15:15 ` Benoît Canet [this message]
2014-07-21 15:35 ` Chris Friesen
2014-07-21 15:54 ` Benoît Canet
2014-07-21 16:10 ` Benoît Canet
2014-08-23 0:59 ` Chris Friesen
2014-08-23 7:56 ` Benoît Canet
2014-08-25 15:12 ` Chris Friesen
2014-08-25 17:43 ` Chris Friesen
2015-08-27 16:37 ` Stefan Hajnoczi
2015-08-27 16:33 ` Stefan Hajnoczi
2014-08-25 21:50 ` Chris Friesen
2014-08-27 5:43 ` Chris Friesen
2015-05-14 13:42 ` Andrey Korolyov
2015-08-26 17:10 ` Andrey Korolyov
2015-08-26 23:31 ` Josh Durgin
2015-08-26 23:47 ` Andrey Korolyov
2015-08-27 0:56 ` Josh Durgin
2015-08-27 16:48 ` Stefan Hajnoczi
2015-08-27 17:05 ` Stefan Hajnoczi
2015-08-27 16:49 ` Stefan Hajnoczi
2015-08-28 0:31 ` Josh Durgin
2015-08-28 8:31 ` Andrey Korolyov
2014-07-21 19:47 ` Benoît Canet
2014-07-21 21:12 ` Chris Friesen
2014-07-21 22:04 ` Benoît Canet
2014-07-18 15:54 ` Andrey Korolyov
2014-07-18 16:26 ` Chris Friesen
2014-07-18 16:30 ` Andrey Korolyov
2014-07-18 16:46 ` Chris Friesen
[not found] <1000957815.25879188.1441820902018.JavaMail.zimbra@redhat.com>
2015-09-09 18:51 ` Jason Dillaman
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