Re: [Xen-users] GPLPV drivers block when copying huge files

[Moritz Mühlenhoff <muehlenhoff@xxxxxxxxxxxxx>]

Hi,

James Harper wrote:
> Not a known problem, but it should be reproducible. I have done some large
> file copying, but your 'huge' and my 'large' may be vastly different - how
> big are the files you are talking about?

The file in question is ca. 9.5 GB large. (Current testing has all been done 
with the same file, since the driver should copy them independantly from the 
binary content of the file. If there's reason to believe it could be 
triggered by file content, we can of couse rerun the tests with a new file of 
similar size).

> How willing are you to run some tests for me? 

Very much, GPLPV is highly useful for free environments of virtualised Windows 
hosts. Thanks for developing it!

> The xennet drivers have no 
> limits on how much memory they could allocate internally for packet
> buffers. I've never seen that as a problem but it's possible that they
> could be running out of resources and not handling that situation properly.
> Alternatively they could be running windows out of resources and windows
> isn't handling that properly.
>
> Can you please test and tell me if the 40% figure changes if you give your
> windows DomU much more or much less memory? I would hope that with much
> less memory it would fail much earlier...

The memory of the target DomU has been raised from 256 MB to 768 MB
and the memory of the source DomU from 512 to 2 GB. This doesn't change 
anything, the copy aborts at the same position and 5-10 pings are lost.

Some further data points: It doesn't make a difference which DomU initiates 
the file transfer, the behaviour is identical. If the other connection point 
is a physical Windows machine, the error is triggered less frequent, but can 
still be reproduced occasionally. The connection is Gigabit-based. 

The Windows event log doesn't show any exceptional log entries.

> It could also be related to gso or csum offload... do things change if you
> disable either of those?

"Checksum Offload" is currently enabled, we'll test disabling it.
Is GSO the same as "Large Send Offload"? If so, we can test it as well.

Cheers,
Moritz
-- 
Moritz Mühlenhoff muehlenhoff@xxxxxxxxxxxxx     fon: +49 421 22 232- 0
Development        Linux for Your Business       fax: +49 421 22 232-99
Univention GmbH    http://www.univention.de/   mobil: +49 175 22 999 23

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