[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Problem with MTU > 1500, ifconfig segmentation fault



Hi again,

I am trying to test the large-MTU fix back-ported to 2.0 from the 3.0 code. Upon testing with "iperf", I am seeing a lot of drops on the RX side. This is happening even when I have MTU set at 1500. Consequently, the TCP throughput reduces drastically. For example here is how the ifconfig counters look like:

On the "iperf -s" host:
         RX packets:4406226 errors:151086 dropped:151086 overruns:0 frame:0
         TX packets:5216687 errors:0 dropped:0 overruns:0 carrier:0

On the "iperf -c" host:
RX packets:5202875 errors:1171787 dropped:1171787 overruns:13775 frame:0
         TX packets:4406204 errors:0 dropped:0 overruns:0 carrier:0

Is there some other dependency between dev_alloc_skb and the network card driver? If there are some places in the code I should be first looking to handle this problem, it would be great to know.

Thank you,
Satish


From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
To: <satish_raghunath@xxxxxxxxxxx>
CC: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Problem with MTU > 1500, ifconfig segmentation fault
Date: Tue, 13 Sep 2005 09:43:18 +0100

On 12 Sep 2005, at 22:48, Satish Raghunath wrote:

I modified the
xen-2.0.7/linux-2.6.11-xen-sparse/arch/xen/kernel/skbuff.c to borrow
changes from the same file in the 3.0 branch. I omitted calls to
"xen_create_contiguous_region" and "xen_destroy_contiguous_region" since
they seemed to call newer hypercalls. The resulting patch is pasted
below. I am able to ping with large frames (up to 8174 bytes). I have
not tested this beyond "ping -s", so I am not sure if this is the right
way to do it.

Is the call to "xen_create_contiguous_region" necessary or is it a
performance enhancement?

The call to xen_create_contiguous_memory() is important, but it's called something else in 2.0 (xen_contig_memory()). It's used in the same way though. The call to xen_destroy_contiguous_memory() can be safely left out.

Without using xen_contig_memory, you'll find that jumbo frames will fail if you do a debug build of Xen.

If you add that in then we'll take the patch. Thanks!

 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

_________________________________________________________________
Take a holiday with a difference. Win a trip to Austria. http://server1.msn.co.in/SP05/CoxKings/index.asp Click for more details


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.