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Re: [Xen-devel] RE: Reducing I/O introduced domain scheduling

To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>, "Dong, Eddie" <eddie.dong@xxxxxxxxx>

From: Keir Fraser <keir@xxxxxxx>

Date: Tue, 12 Oct 2010 10:18:41 +0100

Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>

Delivery-date: Tue, 12 Oct 2010 02:19:49 -0700

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Thread-topic: [Xen-devel] RE: Reducing I/O introduced domain scheduling

No, you can't vmexit on a fence. I don't know whether that matters, so long as buffered writes get flushed before the guest can observe their effects (presumably via some kind of I/O read). Agree that generalising the buffered I/O concept feels a bit dodgy however. -- Keir On 12/10/2010 10:15, "Paul Durrant" <Paul.Durrant@xxxxxxxxxx> wrote: > Just wondering... does Xen/can Xen take VM exits on fences? If not then I > don't see you could safely buffer MMIO writes. > > Paul > >> -----Original Message----- >> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel- >> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Dong, Eddie >> Sent: 12 October 2010 02:12 >> To: Keir Fraser >> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Dong, Eddie; Zhang, Xiantao >> Subject: [Xen-devel] Reducing I/O introduced domain scheduling >> >> Keir: >> When running vConsolidation on top of Xen in a 4-core >> platform, we noticed the I/O introduced scheduling per CPU is ~3K >> Hz, which seems to be too frequent and cause frequent involve of >> domain 0 / Qemu, which may polute cache of the guest and thus >> increase CPI (cycle per instruction). >> >> We are thinking if we can reduce the domin switch here, and >> think the output of I/O can be buffered and return immediately. The >> buffered I/O can be flushed out at next IN emulation (or any >> Hypervisor emulated I/O) or timeout such as 10 or 100 us to >> guarantee minimal response. >> >> Ideally it can cover both PIO & MMIO, but we can start from >> PIO. >> >> How do you think of that? >> >> Thx, Eddie >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@xxxxxxxxxxxxxxxxxxx >> http://lists.xensource.com/xen-devel > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel

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