From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85A2CC77B61 for ; Thu, 27 Apr 2023 08:20:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233120AbjD0IUC (ORCPT ); Thu, 27 Apr 2023 04:20:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242701AbjD0IT5 (ORCPT ); Thu, 27 Apr 2023 04:19:57 -0400 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6B2EF3A9A; Thu, 27 Apr 2023 01:19:55 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0Vh6aTWS_1682583590; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0Vh6aTWS_1682583590) by smtp.aliyun-inc.com; Thu, 27 Apr 2023 16:19:51 +0800 Message-ID: <1682583225.3180113-2-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH] virtio_net: suppress cpu stall when free_unused_bufs Date: Thu, 27 Apr 2023 16:13:45 +0800 From: Xuan Zhuo To: "Michael S. Tsirkin" Cc: Wenliang Wang , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jasowang@redhat.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com References: <20230427043433.2594960-1-wangwenliang.1995@bytedance.com> <1682576442.2203932-1-xuanzhuo@linux.alibaba.com> <252ee222-f918-426e-68ef-b3710a60662e@bytedance.com> <1682579624.5395834-1-xuanzhuo@linux.alibaba.com> <20230427041206-mutt-send-email-mst@kernel.org> In-Reply-To: <20230427041206-mutt-send-email-mst@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 27 Apr 2023 04:12:44 -0400, "Michael S. Tsirkin" wrote: > On Thu, Apr 27, 2023 at 03:13:44PM +0800, Xuan Zhuo wrote: > > On Thu, 27 Apr 2023 15:02:26 +0800, Wenliang Wang wrote: > > > > > > > > > On 4/27/23 2:20 PM, Xuan Zhuo wrote: > > > > On Thu, 27 Apr 2023 12:34:33 +0800, Wenliang Wang wrote: > > > >> For multi-queue and large rx-ring-size use case, the following error > > > > > > > > Cound you give we one number for example? > > > > > > 128 queues and 16K queue_size is typical. > > > > > > > > > > >> occurred when free_unused_bufs: > > > >> rcu: INFO: rcu_sched self-detected stall on CPU. > > > >> > > > >> Signed-off-by: Wenliang Wang > > > >> --- > > > >> drivers/net/virtio_net.c | 1 + > > > >> 1 file changed, 1 insertion(+) > > > >> > > > >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > >> index ea1bd4bb326d..21d8382fd2c7 100644 > > > >> --- a/drivers/net/virtio_net.c > > > >> +++ b/drivers/net/virtio_net.c > > > >> @@ -3565,6 +3565,7 @@ static void free_unused_bufs(struct virtnet_info *vi) > > > >> struct virtqueue *vq = vi->rq[i].vq; > > > >> while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > > >> virtnet_rq_free_unused_buf(vq, buf); > > > >> + schedule(); > > > > > > > > Just for rq? > > > > > > > > Do we need to do the same thing for sq? > > > Rq buffers are pre-allocated, take seconds to free rq unused buffers. > > > > > > Sq unused buffers are much less, so do the same for sq is optional. > > > > I got. > > > > I think we should look for a way, compatible with the less queues or the smaller > > rings. Calling schedule() directly may be not a good way. > > > > Thanks. > > Why isn't it a good way? For the small ring, I don't think it is a good way, maybe we only deal with one buf, then call schedule(). We can call the schedule() after processing a certain number of buffers, or check need_resched () first. Thanks. > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > >> } > > > >> } > > > >> > > > >> -- > > > >> 2.20.1 > > > >> >