From: Jason Wang <jasowang@redhat.com> To: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jason Wang <jasowang@redhat.com> Subject: [PATCH V2 6/6] vhost_net: correctly limit the max pending buffers Date: Fri, 30 Aug 2013 12:29:22 +0800 [thread overview] Message-ID: <1377836962-49780-7-git-send-email-jasowang@redhat.com> (raw) In-Reply-To: <1377836962-49780-1-git-send-email-jasowang@redhat.com> As Michael point out, We used to limit the max pending DMAs to get better cache utilization. But it was not done correctly since it was one done when there's no new buffers submitted from guest. Guest can easily exceeds the limitation by keeping sending packets. So this patch moves the check into main loop. Tests shows about 5%-10% improvement on per cpu throughput for guest tx. But a 5% drop on per cpu transaction rate for a single session TCP_RR. Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/net.c | 15 ++++----------- 1 files changed, 4 insertions(+), 11 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index d09c17c..592e1f2 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -363,6 +363,10 @@ static void handle_tx(struct vhost_net *net) if (zcopy) vhost_zerocopy_signal_used(net, vq); + if ((nvq->upend_idx + vq->num - VHOST_MAX_PEND) % UIO_MAXIOV == + nvq->done_idx) + break; + head = vhost_get_vq_desc(&net->dev, vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in, @@ -372,17 +376,6 @@ static void handle_tx(struct vhost_net *net) break; /* Nothing new? Wait for eventfd to tell us they refilled. */ if (head == vq->num) { - int num_pends; - - /* If more outstanding DMAs, queue the work. - * Handle upend_idx wrap around - */ - num_pends = likely(nvq->upend_idx >= nvq->done_idx) ? - (nvq->upend_idx - nvq->done_idx) : - (nvq->upend_idx + UIO_MAXIOV - - nvq->done_idx); - if (unlikely(num_pends > VHOST_MAX_PEND)) - break; if (unlikely(vhost_enable_notify(&net->dev, vq))) { vhost_disable_notify(&net->dev, vq); continue; -- 1.7.1
WARNING: multiple messages have this Message-ID (diff)
From: Jason Wang <jasowang@redhat.com> To: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH V2 6/6] vhost_net: correctly limit the max pending buffers Date: Fri, 30 Aug 2013 12:29:22 +0800 [thread overview] Message-ID: <1377836962-49780-7-git-send-email-jasowang@redhat.com> (raw) In-Reply-To: <1377836962-49780-1-git-send-email-jasowang@redhat.com> As Michael point out, We used to limit the max pending DMAs to get better cache utilization. But it was not done correctly since it was one done when there's no new buffers submitted from guest. Guest can easily exceeds the limitation by keeping sending packets. So this patch moves the check into main loop. Tests shows about 5%-10% improvement on per cpu throughput for guest tx. But a 5% drop on per cpu transaction rate for a single session TCP_RR. Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/net.c | 15 ++++----------- 1 files changed, 4 insertions(+), 11 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index d09c17c..592e1f2 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -363,6 +363,10 @@ static void handle_tx(struct vhost_net *net) if (zcopy) vhost_zerocopy_signal_used(net, vq); + if ((nvq->upend_idx + vq->num - VHOST_MAX_PEND) % UIO_MAXIOV == + nvq->done_idx) + break; + head = vhost_get_vq_desc(&net->dev, vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in, @@ -372,17 +376,6 @@ static void handle_tx(struct vhost_net *net) break; /* Nothing new? Wait for eventfd to tell us they refilled. */ if (head == vq->num) { - int num_pends; - - /* If more outstanding DMAs, queue the work. - * Handle upend_idx wrap around - */ - num_pends = likely(nvq->upend_idx >= nvq->done_idx) ? - (nvq->upend_idx - nvq->done_idx) : - (nvq->upend_idx + UIO_MAXIOV - - nvq->done_idx); - if (unlikely(num_pends > VHOST_MAX_PEND)) - break; if (unlikely(vhost_enable_notify(&net->dev, vq))) { vhost_disable_notify(&net->dev, vq); continue; -- 1.7.1
next prev parent reply other threads:[~2013-08-30 4:41 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-08-30 4:29 [PATCH V2 0/6] vhost code cleanup and minor enhancement Jason Wang 2013-08-30 4:29 ` Jason Wang 2013-08-30 4:29 ` [PATCH V2 1/6] vhost_net: make vhost_zerocopy_signal_used() returns void Jason Wang 2013-08-30 4:29 ` Jason Wang 2013-09-02 5:51 ` Michael S. Tsirkin 2013-09-02 5:51 ` Michael S. Tsirkin 2013-09-02 6:29 ` Jason Wang 2013-09-02 6:29 ` Jason Wang 2013-08-30 4:29 ` [PATCH V2 2/6] vhost_net: use vhost_add_used_and_signal_n() in vhost_zerocopy_signal_used() Jason Wang 2013-08-30 4:29 ` Jason Wang 2013-09-02 5:50 ` Michael S. Tsirkin 2013-09-02 5:50 ` Michael S. Tsirkin 2013-09-02 6:28 ` Jason Wang 2013-09-02 6:28 ` Jason Wang 2013-08-30 4:29 ` [PATCH V2 3/6] vhost: switch to use vhost_add_used_n() Jason Wang 2013-08-30 4:29 ` Jason Wang 2013-08-30 4:29 ` [PATCH V2 4/6] vhost_net: determine whether or not to use zerocopy at one time Jason Wang 2013-08-30 4:29 ` Jason Wang 2013-08-30 18:35 ` Sergei Shtylyov 2013-08-30 18:35 ` Sergei Shtylyov 2013-09-02 3:15 ` Jason Wang 2013-09-02 3:15 ` Jason Wang 2013-08-30 4:29 ` [PATCH V2 5/6] vhost_net: poll vhost queue after marking DMA is done Jason Wang 2013-08-30 4:29 ` Jason Wang 2013-08-30 16:44 ` Ben Hutchings 2013-08-30 16:44 ` Ben Hutchings 2013-09-02 3:06 ` Jason Wang 2013-09-02 3:06 ` Jason Wang 2014-02-12 7:38 ` Qin Chuanyu 2014-02-12 7:38 ` Qin Chuanyu 2014-02-12 10:06 ` Jason Wang 2014-02-12 10:06 ` Jason Wang 2014-02-12 16:01 ` Michael S. Tsirkin 2014-02-12 16:01 ` Michael S. Tsirkin 2013-08-30 4:29 ` Jason Wang [this message] 2013-08-30 4:29 ` [PATCH V2 6/6] vhost_net: correctly limit the max pending buffers Jason Wang 2013-09-02 5:56 ` Michael S. Tsirkin 2013-09-02 5:56 ` Michael S. Tsirkin 2013-09-02 6:30 ` Jason Wang 2013-09-02 6:30 ` Jason Wang 2013-09-02 8:37 ` Jason Wang
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