WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

[Xen-users] Bad TCP accept performance

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Bad TCP accept performance
From: Carl Byström <cgbystrom@xxxxxxxxx>
Date: Mon, 23 May 2011 18:31:01 +0200
Delivery-date: Mon, 23 May 2011 09:31:57 -0700
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:date:message-id:subject:from:to :content-type; bh=yWplvfeKEwjU/XauQ6TQYR9OxV8uwoFr18bywFlRM2s=; b=wcbd08YB7OdRa6fkYaAqewKCtBM6BbpWJj7maF9COjQzzpkQJ/OROFkP1zCl3KC/kr +Ii9blVJuzbGF+d2aTv5RUVrDdJ6n9Hn6TFXxlMlg4nz7DF4tPff/POJih7PNZsqtV0S ETZsecWuIqbW89bjCgyxJmdEW18u2q1NRtxPA=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=dw3TcROeh8GxNPNAedTQ1DXhYeNhXmIm5HJR230rfJAXPTQDUHxW2zBu/CrBnjUDAy dN+YFYWFV5TtxxSdnEPTuaI0XUZTmgDwlrDKO7wwTxYXFcEH5wCH3yxAKKRXeM0FPn/v Uc7yx93EVYjBHvWAcJRRgOJBj0otJC/9O7tN8=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
I've been running some simple tests trying to find out why the TCP accept() rate has been so low on my Xen guest.
The rate at which I can accept new TCP connections is about five times better on a bare metal machine compared to my guest.
Been using netperf with the TCP_CRR test to simulate this behavior.

I originally posted this question at Server Fault (http://serverfault.com/questions/272483/why-is-tcp-accept-performance-so-bad-under-xen) along with lots of more details how I have performed these tests.
After a suggestion from a user there, I decided to try this list. Judging from the number of views the questions did receive at Server Fault and being top-3 voted at Hacker News, I presume this issue is something a lot of users care about.
One user at HN also reported that this apparently is a known issue and is due to small packet performance, affecting both Xen and KVM.

After collecting feedback from SF and HN users, my question is: what can you do to improve small packet performance in Xen?
Is this a fundamentally difficult problem to solve with Xen or is there a "quick fix"?

Thanks!

--
Carl Byström
_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users
<Prev in Thread] Current Thread [Next in Thread>