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Tsirkin" To: Jason Wang Subject: Re: [PATCH RFC v2 2/4] virtio_net: disable cb aggressively Message-ID: <20210413100314-mutt-send-email-mst@kernel.org> References: <20210413054733.36363-1-mst@redhat.com> <20210413054733.36363-3-mst@redhat.com> <43db5c1e-9908-55bb-6d1a-c6c8d71e2315@redhat.com> MIME-Version: 1.0 In-Reply-To: <43db5c1e-9908-55bb-6d1a-c6c8d71e2315@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Willem de Bruijn , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Jakub Kicinski , Wei Wang , David Miller X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" T24gVHVlLCBBcHIgMTMsIDIwMjEgYXQgMDQ6NTM6MzJQTSArMDgwMCwgSmFzb24gV2FuZyB3cm90 ZToKPiAKPiDlnKggMjAyMS80LzEzIOS4i+WNiDE6NDcsIE1pY2hhZWwgUy4gVHNpcmtpbiDlhpnp gZM6Cj4gPiBUaGVyZSBhcmUgY3VycmVudGx5IHR3byBjYXNlcyB3aGVyZSB3ZSBwb2xsIFRYIHZx IG5vdCBpbiByZXNwb25zZSB0byBhCj4gPiBjYWxsYmFjazogc3RhcnQgeG1pdCBhbmQgcnggbmFw aS4gIFdlIGN1cnJlbnRseSBkbyB0aGlzIHdpdGggY2FsbGJhY2tzCj4gPiBlbmFibGVkIHdoaWNo IGNhbiBjYXVzZSBleHRyYSBpbnRlcnJ1cHRzIGZyb20gdGhlIGNhcmQuICBVc2VkIG5vdCB0byBi ZQo+ID4gYSBiaWcgaXNzdWUgYXMgd2UgcnVuIHdpdGggaW50ZXJydXB0cyBkaXNhYmxlZCBidXQg dGhhdCBpcyBubyBsb25nZXIgdGhlCj4gPiBjYXNlLCBhbmQgaW4gc29tZSBjYXNlcyB0aGUgcmF0 ZSBvZiBzcHVyaW91cyBpbnRlcnJ1cHRzIGlzIHNvIGhpZ2gKPiA+IGxpbnV4IGRldGVjdHMgdGhp cyBhbmQgYWN0dWFsbHkga2lsbHMgdGhlIGludGVycnVwdC4KPiA+IAo+ID4gRml4IHVwIGJ5IGRp c2FibGluZyB0aGUgY2FsbGJhY2tzIGJlZm9yZSBwb2xsaW5nIHRoZSB0eCB2cS4KPiA+IAo+ID4g U2lnbmVkLW9mZi1ieTogTWljaGFlbCBTLiBUc2lya2luIDxtc3RAcmVkaGF0LmNvbT4KPiA+IC0t LQo+ID4gICBkcml2ZXJzL25ldC92aXJ0aW9fbmV0LmMgfCAyICsrCj4gPiAgIDEgZmlsZSBjaGFu Z2VkLCAyIGluc2VydGlvbnMoKykKPiA+IAo+ID4gZGlmZiAtLWdpdCBhL2RyaXZlcnMvbmV0L3Zp cnRpb19uZXQuYyBiL2RyaXZlcnMvbmV0L3ZpcnRpb19uZXQuYwo+ID4gaW5kZXggODJlNTIwZDJj YjEyLi4xNmQ1YWJlZDU4MmMgMTAwNjQ0Cj4gPiAtLS0gYS9kcml2ZXJzL25ldC92aXJ0aW9fbmV0 LmMKPiA+ICsrKyBiL2RyaXZlcnMvbmV0L3ZpcnRpb19uZXQuYwo+ID4gQEAgLTE0MjksNiArMTQy OSw3IEBAIHN0YXRpYyB2b2lkIHZpcnRuZXRfcG9sbF9jbGVhbnR4KHN0cnVjdCByZWNlaXZlX3F1 ZXVlICpycSkKPiA+ICAgCQlyZXR1cm47Cj4gPiAgIAlpZiAoX19uZXRpZl90eF90cnlsb2NrKHR4 cSkpIHsKPiA+ICsJCXZpcnRxdWV1ZV9kaXNhYmxlX2NiKHNxLT52cSk7Cj4gPiAgIAkJZnJlZV9v bGRfeG1pdF9za2JzKHNxLCB0cnVlKTsKPiA+ICAgCQlfX25ldGlmX3R4X3VubG9jayh0eHEpOwo+ IAo+IAo+IEFueSByZWFzb24gdGhhdCB3ZSBkb24ndCBuZWVkIHRvIGVuYWJsZSB0aGUgY2IgaGVy ZT8KCkdvb2QgcG9pbnQgLi4uIHByb2JhYmx5IG9ubHkgaWYgdGhlIHZxIGlzbid0IGVtcHR5IC4u LgoKPiBBbmQgYXMgd2UgZGlzY3Vzc2VkIGluIHRoZSBwYXN0LCBpdCdzIHByb2JhYmx5IHRoZSB0 aW1lIHRvIGhhdmUgYSBzaW5nbGUKPiBOQVBJIGZvciBib3RoIHR4IGFuZCByeD8KPiAKPiBUaGFu a3MKCgpEb25udS4gSSdkIGxpa2UgdG8gZ2V0IGEgbWluaW1hbCBidWdmaXggaW4sIHJlZmFjdG9y aW5nIG9uIHRvcCAuLi4KCj4gCj4gPiAgIAl9Cj4gPiBAQCAtMTU4Miw2ICsxNTgzLDcgQEAgc3Rh dGljIG5ldGRldl90eF90IHN0YXJ0X3htaXQoc3RydWN0IHNrX2J1ZmYgKnNrYiwgc3RydWN0IG5l dF9kZXZpY2UgKmRldikKPiA+ICAgCWJvb2wgdXNlX25hcGkgPSBzcS0+bmFwaS53ZWlnaHQ7Cj4g PiAgIAkvKiBGcmVlIHVwIGFueSBwZW5kaW5nIG9sZCBidWZmZXJzIGJlZm9yZSBxdWV1ZWluZyBu ZXcgb25lcy4gKi8KPiA+ICsJdmlydHF1ZXVlX2Rpc2FibGVfY2Ioc3EtPnZxKTsKPiA+ICAgCWZy ZWVfb2xkX3htaXRfc2ticyhzcSwgZmFsc2UpOwo+ID4gICAJaWYgKHVzZV9uYXBpICYmIGtpY2sp CgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpWaXJ0dWFs aXphdGlvbiBtYWlsaW5nIGxpc3QKVmlydHVhbGl6YXRpb25AbGlzdHMubGludXgtZm91bmRhdGlv bi5vcmcKaHR0cHM6Ly9saXN0cy5saW51eGZvdW5kYXRpb24ub3JnL21haWxtYW4vbGlzdGluZm8v dmlydHVhbGl6YXRpb24= 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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 726CBC433ED for ; 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Tue, 13 Apr 2021 07:33:41 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyTe7rBlLKqCoWn++/O8Aw6yKwfkrflupGRE+nGP0iUf29tGd26k1V89INwAeu3NGikNplrxg== X-Received: by 2002:a1c:f715:: with SMTP id v21mr282029wmh.187.1618324421247; Tue, 13 Apr 2021 07:33:41 -0700 (PDT) Received: from redhat.com ([2a10:8006:2281:0:1994:c627:9eac:1825]) by smtp.gmail.com with ESMTPSA id c6sm19518494wri.32.2021.04.13.07.33.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Apr 2021 07:33:40 -0700 (PDT) Date: Tue, 13 Apr 2021 10:33:36 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: linux-kernel@vger.kernel.org, Jakub Kicinski , Wei Wang , David Miller , netdev@vger.kernel.org, Willem de Bruijn , virtualization@lists.linux-foundation.org Subject: Re: [PATCH RFC v2 2/4] virtio_net: disable cb aggressively Message-ID: <20210413100314-mutt-send-email-mst@kernel.org> References: <20210413054733.36363-1-mst@redhat.com> <20210413054733.36363-3-mst@redhat.com> <43db5c1e-9908-55bb-6d1a-c6c8d71e2315@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <43db5c1e-9908-55bb-6d1a-c6c8d71e2315@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 13, 2021 at 04:53:32PM +0800, Jason Wang wrote: > > 在 2021/4/13 下午1:47, Michael S. Tsirkin 写道: > > There are currently two cases where we poll TX vq not in response to a > > callback: start xmit and rx napi. We currently do this with callbacks > > enabled which can cause extra interrupts from the card. Used not to be > > a big issue as we run with interrupts disabled but that is no longer the > > case, and in some cases the rate of spurious interrupts is so high > > linux detects this and actually kills the interrupt. > > > > Fix up by disabling the callbacks before polling the tx vq. > > > > Signed-off-by: Michael S. Tsirkin > > --- > > 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 82e520d2cb12..16d5abed582c 100644 > > --- a/drivers/net/virtio_net.c > > +++ b/drivers/net/virtio_net.c > > @@ -1429,6 +1429,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) > > return; > > if (__netif_tx_trylock(txq)) { > > + virtqueue_disable_cb(sq->vq); > > free_old_xmit_skbs(sq, true); > > __netif_tx_unlock(txq); > > > Any reason that we don't need to enable the cb here? Good point ... probably only if the vq isn't empty ... > And as we discussed in the past, it's probably the time to have a single > NAPI for both tx and rx? > > Thanks Donnu. I'd like to get a minimal bugfix in, refactoring on top ... > > > } > > @@ -1582,6 +1583,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > > bool use_napi = sq->napi.weight; > > /* Free up any pending old buffers before queueing new ones. */ > > + virtqueue_disable_cb(sq->vq); > > free_old_xmit_skbs(sq, false); > > if (use_napi && kick)