From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zoltan Kiss Subject: Re: [PATCH net-next v2] xen-netback: Rework rx_work_todo Date: Tue, 4 Feb 2014 19:19:00 +0000 Message-ID: <52F13D24.5090405@citrix.com> References: <1389805867-22409-1-git-send-email-zoltan.kiss@citrix.com> <20140120163814.GE11681@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: , , , , , David Miller To: Wei Liu Return-path: In-Reply-To: <20140120163814.GE11681@zion.uk.xensource.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 20/01/14 16:38, Wei Liu wrote: > On Wed, Jan 15, 2014 at 05:11:07PM +0000, Zoltan Kiss wrote: >> The recent patch to fix receive side flow control (11b57f) solved the spinning >> thread problem, however caused an another one. The receive side can stall, if: >> - [THREAD] xenvif_rx_action sets rx_queue_stopped to true >> - [INTERRUPT] interrupt happens, and sets rx_event to true >> - [THREAD] then xenvif_kthread sets rx_event to false >> - [THREAD] rx_work_todo doesn't return true anymore >> >> Also, if interrupt sent but there is still no room in the ring, it take quite a >> long time until xenvif_rx_action realize it. This patch ditch that two variable, >> and rework rx_work_todo. If the thread finds it can't fit more skb's into the >> ring, it saves the last slot estimation into rx_last_skb_slots, otherwise it's >> kept as 0. Then rx_work_todo will check if: >> - there is something to send to the ring (like before) >> - there is space for the topmost packet in the queue >> >> I think that's more natural and optimal thing to test than two bool which are >> set somewhere else. >> >> Signed-off-by: Zoltan Kiss > > Sorry for the delay. > > Paul, thanks for reviewing. > > Acked-by: Wei Liu Hi, This patch haven't made it to net-next yet, maybe because the subject doesn't suggest that this is a bugfix. I suggest to apply it as soon as possible, otherwise netback will be quite broken. Zoli