Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933831Ab2J3PwG (ORCPT ); Tue, 30 Oct 2012 11:52:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34407 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753631Ab2J3PwD (ORCPT ); Tue, 30 Oct 2012 11:52:03 -0400 Date: Tue, 30 Oct 2012 17:54:12 +0200 From: "Michael S. Tsirkin" To: Vlad Yasevich Cc: "David S. Miller" , Eric Dumazet , Andrew Morton , Alexander Duyck , Ian Campbell , 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: reduce vq polling on tx zerocopy Message-ID: <20121030155412.GA7256@redhat.com> References: <3e57e2cde71a4270a8fef395c31f5f0e8a130c28.1351524502.git.mst@redhat.com> <508FF6A1.5060201@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <508FF6A1.5060201@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1750 Lines: 47 On Tue, Oct 30, 2012 at 11:47:45AM -0400, Vlad Yasevich wrote: > On 10/29/2012 11:49 AM, Michael S. Tsirkin wrote: > >It seems that to avoid deadlocks it is enough to poll vq before > > we are going to use the last buffer. This should be faster than > >c70aa540c7a9f67add11ad3161096fb95233aa2e. > > > >Signed-off-by: Michael S. Tsirkin > >--- > > drivers/vhost/net.c | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > > > >diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > >index 8e9de79..3967f82 100644 > >--- a/drivers/vhost/net.c > >+++ b/drivers/vhost/net.c > >@@ -197,8 +197,16 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status) > > { > > struct vhost_ubuf_ref *ubufs = ubuf->ctx; > > struct vhost_virtqueue *vq = ubufs->vq; > >- > >- vhost_poll_queue(&vq->poll); > >+ int cnt = atomic_read(&ubufs->kref.refcount); > >+ > >+ /* > >+ * Trigger polling thread if guest stopped submitting new buffers: > >+ * in this case, the refcount after decrement will eventually reach 1 > >+ * so here it is 2. > >+ * We also trigger polling periodically after each 16 packets. > >+ */ > >+ if (cnt <= 2 || !(cnt % 16)) > > Why 16? Does it make sense to make it configurable? > > -vlad Probably not but I'll add a comment explaining why. > >+ vhost_poll_queue(&vq->poll); > > /* set len to mark this desc buffers done DMA */ > > vq->heads[ubuf->desc].len = status ? > > VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN; > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/