| Message ID | 20210413054733.36363-3-mst@redhat.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio net: spurious interrupt related fixes | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Guessed tree name to be net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 6 of 6 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 14 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
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 <mst@redhat.com> > --- > 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? And as we discussed in the past, it's probably the time to have a single NAPI for both tx and rx? Thanks > } > @@ -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)
On Tue, Apr 13, 2021 at 4:53 AM Jason Wang <jasowang@redhat.com> 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 <mst@redhat.com> > > --- > > 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? This is an opportunistic clean outside the normal tx-napi path, so if disabling the tx interrupt here, it won't be reenabled based on napi_complete_done. I think that means that it stays disabled until the following start_xmit: if (use_napi && kick) virtqueue_enable_cb_delayed(sq->vq); But that seems sufficient.
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 <mst@redhat.com> > > --- > > 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)
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); } @@ -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)
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 <mst@redhat.com> --- drivers/net/virtio_net.c | 2 ++ 1 file changed, 2 insertions(+)