From: "Christopher G. Stach II" <cgs@ldsys.net>
To: George Dunlap <gdunlap@xensource.com>
Cc: xen-devel <xen-devel@lists.xensource.com>,
Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk>,
Liang Yang <multisyncfe991@hotmail.com>,
Emmanuel Ackaouy <ack@xensource.com>,
John Byrne <john.l.byrne@hp.com>
Subject: Re: Performance data of Linux native vs. Xen Dom0 and Xen DomU. Re: Direct I/O to domU seeing a 30% performance hit
Date: Mon, 13 Nov 2006 09:49:33 -0600 [thread overview]
Message-ID: <4558940D.2010200@ldsys.net> (raw)
In-Reply-To: <de76405a0611071053g2e854998o3359b31010086fa9@mail.gmail.com>
George Dunlap wrote:
> One of the strange things, though, is that the difference should be so
> big between domU and dom0, which are using the exact same same kernel
> (correct me if I'm wrong).
>
> I'm not familiar with the I/O scheduling. Is it possible that the I/O
> scheduling inside the domU is interacting poorly with the I/O
> scheduling in dom0? That's one hypothesis for why domU writes are
> slower than dom0 writes; but that doesn't seem to explain why domU
> reads would be *faster* than dom0 reads.
>
> -George
Correct me if I'm wrong, but wouldn't a file-backed block device for the
domU be reading from memory if it's cached in the dom0? That would be a
bit faster.
Also, in the past it seemed the domU schedulers were ignored and were
implicitly noop, relying on the dom0's scheduler (which did all of the
real I/O.) Has this changed?
--
Christopher G. Stach II
next prev parent reply other threads:[~2006-11-13 15:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-07 18:45 Performance data of Linux native vs. Xen Dom0 and Xen DomU. Re: Direct I/O to domU seeing a 30% performance hit Ian Pratt
2006-11-07 18:53 ` George Dunlap
2006-11-09 0:43 ` Xen DomU (vt-x) reports CPU utilization ZERO!!! Liang Yang
2006-11-13 15:49 ` Christopher G. Stach II [this message]
2006-11-13 16:18 ` Performance data of Linux native vs. Xen Dom0 and Xen DomU. Re: Direct I/O to domU seeing a 30% performance hit Liang Yang
2006-11-07 18:55 ` Liang Yang
-- strict thread matches above, loose matches on Subject: below --
2006-11-07 12:18 Ian Pratt
2006-11-07 16:44 ` John Byrne
2006-11-07 17:20 ` Ian Pratt
2006-11-07 17:40 ` Performance data of Linux native vs. Xen Dom0 and Xen DomU. " Liang Yang
2006-11-07 18:06 ` Ian Pratt
2006-11-07 18:10 ` Liang Yang
2006-11-07 18:15 ` Ian Pratt
2006-11-07 18:23 ` Liang Yang
2006-11-07 18:40 ` George Dunlap
2006-11-07 18:46 ` Liang Yang
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