From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCHv1 net] xen-netback: support frontends without feature-rx-notify again Date: Mon, 5 Jan 2015 11:51:43 +0000 Message-ID: <1420458703.22423.30.camel@citrix.com> References: <1418901186-14478-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: , , Wei Liu To: David Vrabel , James Harper Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:14014 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218AbbAELwB (ORCPT ); Mon, 5 Jan 2015 06:52:01 -0500 In-Reply-To: <1418901186-14478-1-git-send-email-david.vrabel@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2014-12-18 at 11:13 +0000, David Vrabel wrote: > Commit bc96f648df1bbc2729abbb84513cf4f64273a1f1 (xen-netback: make > feature-rx-notify mandatory) incorrectly assumed that there were no > frontends in use that did not support this feature. But the frontend > driver in MiniOS does not and since this is used by (qemu) stubdoms, > these stopped working. > > Netback sort of works as-is in this mode except: > > - If there are no Rx requests and the internal Rx queue fills, only > the drain timeout will wake the thread. The default drain timeout > of 10 s would give unacceptable pauses. > > - If an Rx stall was detected and the internal Rx queue is drained, > then the Rx thread would never wake. > > Handle these two cases (when feature-rx-notify is disabled) by: > > - Reducing the drain timeout to 30 ms. > > - Disabling Rx stall detection. > > Reported-by: John > Tested-by: John > Signed-off-by: David Vrabel FYI I've seen a report[0] that "Windows 2012 R2 domu with GPLPV drivers" also suffered without feature-rx-notify support in the backend. Ian. [0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=767261#103