Re: [Xen-devel] Rather slow time of Pin in Windows with GPL PV driver

[John Weekes <lists.xen@xxxxxxxxxxxxxxxxxx>]

On 3/8/2011 10:53 PM, MaoXiaoyun wrote:
> Attached is the linux and Win2003 Ping result, which shows
> in Linux, the time is less than 1ms, and very stable, while in 2003,
> Ping time, minium to lese than 1ms, and maxium to 15ms, unstable.
>
> Those two HVMS is on the same host, we also test XP, 2008,
> and it looks like Ping on XP behavior normally, but in 2008, it has the
> same behavior as 2003.

This may not completely account for it, but try enabling the multimedia
timer on your Windows installs by starting up any application that asks
to use it at a 1ms resolution, such as Windows Media Player. Seeing RTTs
that are either 1ms or 15ms, but never a number in between, is a
tell-tale sign that the MM timer is not currently in use, and as a
result you're getting less accurate, more granular readings.

-John

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