From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCH 3/3] xen-netback: reintroduce guest Rx stall detection Date: Thu, 23 Oct 2014 12:49:52 +0100 Message-ID: <20141023114952.GI9188@zion.uk.xensource.com> References: <1413983335-8307-1-git-send-email-david.vrabel@citrix.com> <1413983335-8307-4-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: , , Ian Campbell , Wei Liu To: David Vrabel Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:53991 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754146AbaJWLtx (ORCPT ); Thu, 23 Oct 2014 07:49:53 -0400 Content-Disposition: inline In-Reply-To: <1413983335-8307-4-git-send-email-david.vrabel@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Oct 22, 2014 at 02:08:55PM +0100, David Vrabel wrote: > If a frontend not receiving packets it is useful to detect this and > turn off the carrier so packets are dropped early instead of being > queued and drained when they expire. > > A to-guest queue is stalled if it doesn't have enough free slots for a > an extended period of time (default 60 s). > > If at least one queue is stalled, the carrier is turned off (in the > expectation that the other queues will soon stall as well). The > carrier is only turned on once all queues are ready. > > When the frontend connects, all the queues start in the stalled state > and only become ready once the frontend queues enough Rx requests. > > Signed-off-by: David Vrabel Reviewed-by: Wei Liu