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 04123C77B75 for ; Mon, 8 May 2023 06:08:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232736AbjEHGIq (ORCPT ); Mon, 8 May 2023 02:08:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231779AbjEHGIn (ORCPT ); Mon, 8 May 2023 02:08:43 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34E6513875 for ; Sun, 7 May 2023 23:08:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683526084; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=496riEt70CLjVEPXxKBFIzM6DccwKHKgAN0XgS7K+xk=; b=WU3MR5nPwyORCS4PDfIDUkkSu3M9zLSEngYD76mv+AO7vSBezbqusIT1qIq9bMi+o9Kni5 eJ3KJa3nYJ5lajV9cBqiMcdG3l1G1jJ1ruJgT8Z+O5JdUVuqBJwkdEMM3rLmJSk4goWcHm Es7bUys3H2Xczgetv6iWj1C9fC2+xAs= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-326-bzsvHkrjNFa2-JndIPgE7g-1; Mon, 08 May 2023 02:08:03 -0400 X-MC-Unique: bzsvHkrjNFa2-JndIPgE7g-1 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-30641258c9eso1359709f8f.2 for ; Sun, 07 May 2023 23:08:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683526082; x=1686118082; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=496riEt70CLjVEPXxKBFIzM6DccwKHKgAN0XgS7K+xk=; b=SkgpRetj6l/hsB9vOOf6gWmK0UeXmxxSBGEd7jjxXlOqORLzaRSt9U70wtpg/s/hP0 6hgyyb6HXNVmnClkiGLHb8vNrmpCAWXrLomwhQwqXFCLX77gF/TOdPgBJVZKSX5lJW7h 7S7h5xc+mVWzVkSpon/0A2+QULXaHQ2QPulGYfMz1PO1cOJyhC7ifIb/pF4TsorzYenD w5OyRsAsmP9GwtNzlpe2mBvLc34KUbvSsZElMHhPyVpCmNx1orrM75s5U4AuYup4Lp5L emdfCXPpQbz6ozzLcwtSvWDro1Yk+gaSRflgl05wZ6GcLR0bZecjUcZ7hDITB26QnNLo mq6A== X-Gm-Message-State: AC+VfDw/4N0CDrF6U+MxjkD1Fubtsotz8wEvPE+WGXkAfF0lgKkA3ZFO p63NfVxXI5a5KicMwSgeiWWnl+TI8y5dEkETlPOo2WvLjskz3uD57Ghe599xqZULz6NbU601G/j biM3E/YXgCSstOf2cBGrajBnH X-Received: by 2002:a5d:6801:0:b0:306:2b64:fd1b with SMTP id w1-20020a5d6801000000b003062b64fd1bmr6387823wru.52.1683526082131; Sun, 07 May 2023 23:08:02 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ7f8poeeWKuFbkFRFraXJPQPQU8mq+PdFxmJfqKohdU/FLK+Ng7mCXc+1OoWwdFP0rxufKFDA== X-Received: by 2002:a5d:6801:0:b0:306:2b64:fd1b with SMTP id w1-20020a5d6801000000b003062b64fd1bmr6387812wru.52.1683526081830; Sun, 07 May 2023 23:08:01 -0700 (PDT) Received: from redhat.com ([2.52.158.28]) by smtp.gmail.com with ESMTPSA id k15-20020a5d428f000000b003062d815fa6sm10182362wrq.85.2023.05.07.23.07.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 07 May 2023 23:08:01 -0700 (PDT) Date: Mon, 8 May 2023 02:07:57 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: Wenliang Wang , davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, zhengqi.arch@bytedance.com, willemdebruijn.kernel@gmail.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, xuanzhuo@linux.alibaba.com Subject: Re: [PATCH v4] virtio_net: suppress cpu stall when free_unused_bufs Message-ID: <20230508020717-mutt-send-email-mst@kernel.org> References: <1683167226-7012-1-git-send-email-wangwenliang.1995@bytedance.com> <20230507093328-mutt-send-email-mst@kernel.org> <2b5cf90a-efa8-52a7-9277-77722622c128@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2b5cf90a-efa8-52a7-9277-77722622c128@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 08, 2023 at 11:12:03AM +0800, Jason Wang wrote: > > 在 2023/5/7 21:34, Michael S. Tsirkin 写道: > > On Fri, May 05, 2023 at 11:28:25AM +0800, Jason Wang wrote: > > > On Thu, May 4, 2023 at 10:27 AM Wenliang Wang > > > wrote: > > > > For multi-queue and large ring-size use case, the following error > > > > occurred when free_unused_bufs: > > > > rcu: INFO: rcu_sched self-detected stall on CPU. > > > > > > > > Fixes: 986a4f4d452d ("virtio_net: multiqueue support") > > > > Signed-off-by: Wenliang Wang > > > > --- > > > > v2: > > > > -add need_resched check. > > > > -apply same logic to sq. > > > > v3: > > > > -use cond_resched instead. > > > > v4: > > > > -add fixes tag > > > > --- > > > > drivers/net/virtio_net.c | 2 ++ > > > > 1 file changed, 2 insertions(+) > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > index 8d8038538fc4..a12ae26db0e2 100644 > > > > --- a/drivers/net/virtio_net.c > > > > +++ b/drivers/net/virtio_net.c > > > > @@ -3560,12 +3560,14 @@ static void free_unused_bufs(struct virtnet_info *vi) > > > > struct virtqueue *vq = vi->sq[i].vq; > > > > while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > > > virtnet_sq_free_unused_buf(vq, buf); > > > > + cond_resched(); > > > Does this really address the case when the virtqueue is very large? > > > > > > Thanks > > > > it does in that a very large queue is still just 64k in size. > > we might however have 64k of these queues. > > > Ok, but we have other similar loops especially the refill, I think we may > need cond_resched() there as well. > > Thanks > Refill is already per vq isn't it? > > > > > > } > > > > > > > > for (i = 0; i < vi->max_queue_pairs; i++) { > > > > struct virtqueue *vq = vi->rq[i].vq; > > > > while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > > > virtnet_rq_free_unused_buf(vq, buf); > > > > + cond_resched(); > > > > } > > > > } > > > > > > > > -- > > > > 2.20.1 > > > >