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RE: [Xen-devel] BSoD with GPLPV + tap:aio

To: "Paul Durrant" <paul.durrant@xxxxxxxxxx>
Subject: RE: [Xen-devel] BSoD with GPLPV + tap:aio
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Mon, 9 Nov 2009 21:15:37 +1100
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Thread-topic: [Xen-devel] BSoD with GPLPV + tap:aio
> 
> James Harper wrote:
> >
> > No PnP. I/O was being saturated though - I was performing a restore
via
> > network to the disk on the machine that crashed.
> >
> > Using phy: or file: I can restore 600GB with no problems at all.
With
> > tap:aio it crashes after a few tens of GB.
> >
> 
> Another guess then... tap will probably have more outstanding
> transactions than back as its datapath is likely to be longer and so
is
> higher latency. Is your frontend overflowing a queue of outstanding
SRBs?
> 

Thanks, that's a good lead. I think Windows is pretty limiting in the
amount of outstanding I/O that it allows (16 outstanding requests?) but
maybe that is too much for tap... I'll double check that I am catering
for a ring-full condition.

James

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