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RE: [Xen-devel] [Patch 0/7] pvSCSI driver

To: "Jun Kamada" <kama@xxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [Patch 0/7] pvSCSI driver
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Thu, 21 Feb 2008 14:39:47 +1100
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Thread-topic: [Xen-devel] [Patch 0/7] pvSCSI driver
> Another issue I've come across - you appear to have hardcoded the
> timeout to 5 seconds. I'm trying to run the HP Library & Tape Tools
> under windows, and things like unload and erase go well beyond the 5
> seconds you allow. I increased the timeout to 30 seconds and the
> works fine but the erase goes for longer than that.
> I notice you have a timeout field in the request field, but have
> commented it out. What was the reason for this?

Just responding to myself, would I be guessing correctly that you
removed the timeout field to make the request structure smaller? The top
byte of the request_bufflen field could be used as a timeout, as
sensible timeout values don't need to be very exact. Even if we just
used the top 4 bits and made it (1 << (timeout + 1)) * 5 * HZ, that
would give us a bit over 45 hours, and we'd make 15 mean infinite.

By my calculations, the largest that bufflen could be is 27 * PAGE_SIZE
= ~110K on x86, so we have plenty of headroom.

With the timeout increased, the HP Library & Tape Tools have
successfully completed a 'LTO Drive Assessment test' under Windows.


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