RE: [Xen-users] performance of pv drivers for windows

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> > Please run debugview from sysinternals.com while you are running
your
> > disk performance testing. It will periodically output some stats
like:
> >
> > XenVbd     stat_interrupts = 2408914
> > XenVbd     stat_interrupts_for_me = 314368
> > XenVbd     stat_reads = 131507
> > XenVbd     stat_writes = 208567
> > XenVbd     stat_unaligned_le_4096 = 7
> > XenVbd     stat_unaligned_le_8192 = 0
> > XenVbd     stat_unaligned_le_16384 = 0
> > XenVbd     stat_unaligned_le_32768 = 0
> > XenVbd     stat_unaligned_le_65536 = 0
> > XenVbd     stat_unaligned_gt_65536 = 0
> > XenVbd     stat_no_shadows = 0
> > XenVbd     stat_no_grants = 0
> > XenVbd     stat_outstanding_requests = 1
> >
> > The things I'm interested in are that stat_unaligned_xxx figures.
The
> > only unaligned requests I see during day to day operations are
somewhere
> > between 5 and 10 that occur very very early during boot
> > (stat_unaligned_le_4096 = 7). However I have seen chkdsk, defrag,
and at
> > least one testing tool issue requests not aligned on 512 byte
> > boundaries. When that happens, the gplpv drivers have to break the
> > request into 4096 byte chunks and submit each chunk, one at a time,
to
> > blkback, which really slows things down.
> I had that tool running, but it did not produced any output, I guess I
> used it
> in a wrong manner ;).
> 

You need to make sure that kernel debug message capture is on. In the
'Capture' menu, make sure that 'Capture Kernel' is ticked.

Thanks

james

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