From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dor Laor Subject: [PATCH] virtio_net tx performance fix Date: Mon, 28 Jan 2008 02:13:44 +0200 Message-ID: <1201479224.3047.37.camel@localhost.localdomain> Reply-To: dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="=-1QR0LBtRKc/Zc5Nzqh1U" To: Rusty Russell , Anthony Liguori , kvm-devel , "virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org --=-1QR0LBtRKc/Zc5Nzqh1U Content-Type: text/plain Content-Transfer-Encoding: 7bit >>From f582caf612b446e42f1e80d5ef12c5b7322efd03 Mon Sep 17 00:00:00 2001 From: Dor Laor Date: Mon, 28 Jan 2008 02:09:48 +0200 Subject: [PATCH] virtio_net tx performance fix There was a problem with the location of the notify call in add_buff function: When VRING_USED_F_NO_NOTIFY is set, the host does not kick the guest when packets were transmitted, as a result the guest runs out of tx buffers sometimes. This is fine but the problem lies when add_buf fails, it called notify and the host sends all the pending tx pkts. When enable_cb was called, more_used(vq) returned false so eventually the skb was dropped. Moving notify from add_buf to enable_cb fixes this flow problem. The tx performance boosted from 220Mbps to 850Mbps. Signed-off-by: Dor Laor --- drivers/virtio/virtio_ring.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 3a28c13..592bbc9 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -87,8 +87,6 @@ static int vring_add_buf(struct virtqueue *_vq, if (vq->num_free < out + in) { pr_debug("Can't add buf len %i - avail = %i\n", out + in, vq->num_free); - /* We notify *even if* VRING_USED_F_NO_NOTIFY is set here. */ - vq->notify(&vq->vq); END_USE(vq); return -ENOSPC; } @@ -232,6 +230,7 @@ static bool vring_enable_cb(struct virtqueue *_vq) vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; mb(); if (unlikely(more_used(vq))) { + vq->notify(&vq->vq); vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; END_USE(vq); return false; -- 1.5.3.7 --=-1QR0LBtRKc/Zc5Nzqh1U Content-Disposition: attachment; filename=0001-virtio_net-tx-performance-fix.patch Content-Type: application/mbox; name=0001-virtio_net-tx-performance-fix.patch Content-Transfer-Encoding: 7bit >>From f582caf612b446e42f1e80d5ef12c5b7322efd03 Mon Sep 17 00:00:00 2001 From: Dor Laor Date: Mon, 28 Jan 2008 02:09:48 +0200 Subject: [PATCH] virtio_net tx performance fix There was a problem with the location of the notify call in add_buff function: When VRING_USED_F_NO_NOTIFY is set, the host does not kick the guest when packets were transmited, as a result the guest runs out of tx buffers sometimes. This is fine but the problem lies when add_buf fails, it called notify and the host sends all the pending tx pkts. When enable_cb was called, more_used(vq) returned false so eventually the skb was droped. Moving notify from add_buf to enable_cb fixes this flow problem. The tx performance boosted from 220Mbps to 850Mbps. Signed-off-by: Dor Laor --- drivers/virtio/virtio_ring.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 3a28c13..592bbc9 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -87,8 +87,6 @@ static int vring_add_buf(struct virtqueue *_vq, if (vq->num_free < out + in) { pr_debug("Can't add buf len %i - avail = %i\n", out + in, vq->num_free); - /* We notify *even if* VRING_USED_F_NO_NOTIFY is set here. */ - vq->notify(&vq->vq); END_USE(vq); return -ENOSPC; } @@ -232,6 +230,7 @@ static bool vring_enable_cb(struct virtqueue *_vq) vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; mb(); if (unlikely(more_used(vq))) { + vq->notify(&vq->vq); vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; END_USE(vq); return false; -- 1.5.3.7 --=-1QR0LBtRKc/Zc5Nzqh1U Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ --=-1QR0LBtRKc/Zc5Nzqh1U Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ kvm-devel mailing list kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/kvm-devel --=-1QR0LBtRKc/Zc5Nzqh1U--