From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754280AbdC3Cdh (ORCPT ); Wed, 29 Mar 2017 22:33:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41166 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753284AbdC3Cdf (ORCPT ); Wed, 29 Mar 2017 22:33:35 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 301816AAC0 Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=mst@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 301816AAC0 Date: Thu, 30 Mar 2017 05:33:33 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 8/8] vhost_net: use lockless peeking for skb array during busy polling Message-ID: <20170330053315-mutt-send-email-mst@kernel.org> References: <1490069087-4783-1-git-send-email-jasowang@redhat.com> <1490069087-4783-9-git-send-email-jasowang@redhat.com> <20170329150538-mutt-send-email-mst@kernel.org> <104c0c1f-e2fd-f5d0-0aae-c308d1f1373c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <104c0c1f-e2fd-f5d0-0aae-c308d1f1373c@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 30 Mar 2017 02:33:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 30, 2017 at 10:16:15AM +0800, Jason Wang wrote: > > > On 2017年03月29日 20:07, Michael S. Tsirkin wrote: > > On Tue, Mar 21, 2017 at 12:04:47PM +0800, Jason Wang wrote: > > > For the socket that exports its skb array, we can use lockless polling > > > to avoid touching spinlock during busy polling. > > > > > > Signed-off-by: Jason Wang > > > --- > > > drivers/vhost/net.c | 7 +++++-- > > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > > index 53f09f2..41153a3 100644 > > > --- a/drivers/vhost/net.c > > > +++ b/drivers/vhost/net.c > > > @@ -551,10 +551,13 @@ static int peek_head_len(struct vhost_net_virtqueue *rvq, struct sock *sk) > > > return len; > > > } > > > -static int sk_has_rx_data(struct sock *sk) > > > +static int sk_has_rx_data(struct vhost_net_virtqueue *rvq, struct sock *sk) > > > { > > > struct socket *sock = sk->sk_socket; > > > + if (rvq->rx_array) > > > + return !__skb_array_empty(rvq->rx_array); > > > + > > > if (sock->ops->peek_len) > > > return sock->ops->peek_len(sock); > > I don't see which patch adds __skb_array_empty. > > This is not something new, it was introduced by ad69f35d1dc0a ("skb_array: > array based FIFO for skbs"). > > Thanks Same comment about a compiler barrier applies then. > > > > > @@ -579,7 +582,7 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, > > > endtime = busy_clock() + vq->busyloop_timeout; > > > while (vhost_can_busy_poll(&net->dev, endtime) && > > > - !sk_has_rx_data(sk) && > > > + !sk_has_rx_data(rvq, sk) && > > > vhost_vq_avail_empty(&net->dev, vq)) > > > cpu_relax(); > > > -- > > > 2.7.4 From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net-next 8/8] vhost_net: use lockless peeking for skb array during busy polling Date: Thu, 30 Mar 2017 05:33:33 +0300 Message-ID: <20170330053315-mutt-send-email-mst@kernel.org> References: <1490069087-4783-1-git-send-email-jasowang@redhat.com> <1490069087-4783-9-git-send-email-jasowang@redhat.com> <20170329150538-mutt-send-email-mst@kernel.org> <104c0c1f-e2fd-f5d0-0aae-c308d1f1373c@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <104c0c1f-e2fd-f5d0-0aae-c308d1f1373c@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org T24gVGh1LCBNYXIgMzAsIDIwMTcgYXQgMTA6MTY6MTVBTSArMDgwMCwgSmFzb24gV2FuZyB3cm90 ZToKPiAKPiAKPiBPbiAyMDE35bm0MDPmnIgyOeaXpSAyMDowNywgTWljaGFlbCBTLiBUc2lya2lu IHdyb3RlOgo+ID4gT24gVHVlLCBNYXIgMjEsIDIwMTcgYXQgMTI6MDQ6NDdQTSArMDgwMCwgSmFz b24gV2FuZyB3cm90ZToKPiA+ID4gRm9yIHRoZSBzb2NrZXQgdGhhdCBleHBvcnRzIGl0cyBza2Ig YXJyYXksIHdlIGNhbiB1c2UgbG9ja2xlc3MgcG9sbGluZwo+ID4gPiB0byBhdm9pZCB0b3VjaGlu ZyBzcGlubG9jayBkdXJpbmcgYnVzeSBwb2xsaW5nLgo+ID4gPiAKPiA+ID4gU2lnbmVkLW9mZi1i eTogSmFzb24gV2FuZyA8amFzb3dhbmdAcmVkaGF0LmNvbT4KPiA+ID4gLS0tCj4gPiA+ICAgZHJp dmVycy92aG9zdC9uZXQuYyB8IDcgKysrKystLQo+ID4gPiAgIDEgZmlsZSBjaGFuZ2VkLCA1IGlu c2VydGlvbnMoKyksIDIgZGVsZXRpb25zKC0pCj4gPiA+IAo+ID4gPiBkaWZmIC0tZ2l0IGEvZHJp dmVycy92aG9zdC9uZXQuYyBiL2RyaXZlcnMvdmhvc3QvbmV0LmMKPiA+ID4gaW5kZXggNTNmMDlm Mi4uNDExNTNhMyAxMDA2NDQKPiA+ID4gLS0tIGEvZHJpdmVycy92aG9zdC9uZXQuYwo+ID4gPiAr KysgYi9kcml2ZXJzL3Zob3N0L25ldC5jCj4gPiA+IEBAIC01NTEsMTAgKzU1MSwxMyBAQCBzdGF0 aWMgaW50IHBlZWtfaGVhZF9sZW4oc3RydWN0IHZob3N0X25ldF92aXJ0cXVldWUgKnJ2cSwgc3Ry dWN0IHNvY2sgKnNrKQo+ID4gPiAgIAlyZXR1cm4gbGVuOwo+ID4gPiAgIH0KPiA+ID4gLXN0YXRp YyBpbnQgc2tfaGFzX3J4X2RhdGEoc3RydWN0IHNvY2sgKnNrKQo+ID4gPiArc3RhdGljIGludCBz a19oYXNfcnhfZGF0YShzdHJ1Y3Qgdmhvc3RfbmV0X3ZpcnRxdWV1ZSAqcnZxLCBzdHJ1Y3Qgc29j ayAqc2spCj4gPiA+ICAgewo+ID4gPiAgIAlzdHJ1Y3Qgc29ja2V0ICpzb2NrID0gc2stPnNrX3Nv Y2tldDsKPiA+ID4gKwlpZiAocnZxLT5yeF9hcnJheSkKPiA+ID4gKwkJcmV0dXJuICFfX3NrYl9h cnJheV9lbXB0eShydnEtPnJ4X2FycmF5KTsKPiA+ID4gKwo+ID4gPiAgIAlpZiAoc29jay0+b3Bz LT5wZWVrX2xlbikKPiA+ID4gICAJCXJldHVybiBzb2NrLT5vcHMtPnBlZWtfbGVuKHNvY2spOwo+ ID4gSSBkb24ndCBzZWUgd2hpY2ggcGF0Y2ggYWRkcyBfX3NrYl9hcnJheV9lbXB0eS4KPiAKPiBU aGlzIGlzIG5vdCBzb21ldGhpbmcgbmV3LCBpdCB3YXMgaW50cm9kdWNlZCBieSBhZDY5ZjM1ZDFk YzBhICgic2tiX2FycmF5Ogo+IGFycmF5IGJhc2VkIEZJRk8gZm9yIHNrYnMiKS4KPiAKPiBUaGFu a3MKClNhbWUgY29tbWVudCBhYm91dCBhIGNvbXBpbGVyIGJhcnJpZXIgYXBwbGllcyB0aGVuLgoK PiA+IAo+ID4gPiBAQCAtNTc5LDcgKzU4Miw3IEBAIHN0YXRpYyBpbnQgdmhvc3RfbmV0X3J4X3Bl ZWtfaGVhZF9sZW4oc3RydWN0IHZob3N0X25ldCAqbmV0LAo+ID4gPiAgIAkJZW5kdGltZSA9IGJ1 c3lfY2xvY2soKSArIHZxLT5idXN5bG9vcF90aW1lb3V0Owo+ID4gPiAgIAkJd2hpbGUgKHZob3N0 X2Nhbl9idXN5X3BvbGwoJm5ldC0+ZGV2LCBlbmR0aW1lKSAmJgo+ID4gPiAtCQkgICAgICAgIXNr X2hhc19yeF9kYXRhKHNrKSAmJgo+ID4gPiArCQkgICAgICAgIXNrX2hhc19yeF9kYXRhKHJ2cSwg c2spICYmCj4gPiA+ICAgCQkgICAgICAgdmhvc3RfdnFfYXZhaWxfZW1wdHkoJm5ldC0+ZGV2LCB2 cSkpCj4gPiA+ICAgCQkJY3B1X3JlbGF4KCk7Cj4gPiA+IC0tIAo+ID4gPiAyLjcuNApfX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpWaXJ0dWFsaXphdGlvbiBt YWlsaW5nIGxpc3QKVmlydHVhbGl6YXRpb25AbGlzdHMubGludXgtZm91bmRhdGlvbi5vcmcKaHR0 cHM6Ly9saXN0cy5saW51eGZvdW5kYXRpb24ub3JnL21haWxtYW4vbGlzdGluZm8vdmlydHVhbGl6 YXRpb24=