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Tsirkin" To: Daniel Jurgens Cc: "netdev@vger.kernel.org" , "jasowang@redhat.com" , "xuanzhuo@linux.alibaba.com" , "virtualization@lists.linux.dev" , "davem@davemloft.net" , "edumazet@google.com" , "kuba@kernel.org" , "abeni@redhat.com" , Parav Pandit Subject: Re: [PATCH net-next] virtio_net: Add TX stop and wake counters Message-ID: <20240130105246-mutt-send-email-mst@kernel.org> References: <20240130142521.18593-1-danielj@nvidia.com> <20240130095645-mutt-send-email-mst@kernel.org> <20240130104107-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jan 30, 2024 at 03:50:29PM +0000, Daniel Jurgens wrote: > > From: Michael S. Tsirkin > > Sent: Tuesday, January 30, 2024 9:42 AM > > On Tue, Jan 30, 2024 at 03:40:21PM +0000, Daniel Jurgens wrote: > > > > From: Michael S. Tsirkin > > > > Sent: Tuesday, January 30, 2024 8:58 AM > > > > > > > > On Tue, Jan 30, 2024 at 08:25:21AM -0600, Daniel Jurgens wrote: > > > > > Add a tx queue stop and wake counters, they are useful for debugging. > > > > > > > > > > $ ethtool -S ens5f2 | grep 'tx_stop\|tx_wake' > > > > > ... > > > > > tx_queue_1_tx_stop: 16726 > > > > > tx_queue_1_tx_wake: 16726 > > > > > ... > > > > > tx_queue_8_tx_stop: 1500110 > > > > > tx_queue_8_tx_wake: 1500110 > > > > > > > > > > Signed-off-by: Daniel Jurgens > > > > > Reviewed-by: Parav Pandit > > > > > > > > Hmm isn't one always same as the other, except when queue is stopped? > > > > And when it is stopped you can see that in the status? > > > > So how is having two useful? > > > > > > At idle the counters will be the same, unless a tx_timeout occurs. But > > under load they can be monitored to see which queues are stopped and get > > an idea of how long they are stopped. > > > > how does it give you the idea of how long they are stopped? > > By serially monitoring the counter you can see stops that persist long intervals that are less than the tx_timeout time. Why don't you monitor queue status directly? > > > > > Other net drivers (not all), also have the wake counter. > > > > Examples? > > [danielj@sw-mtx-051 upstream]$ ethtool -i ens2f1np1 > driver: mlx5_core > version: 6.7.0+ > ... > [danielj@sw-mtx-051 upstream]$ ethtool -S ens2f1np1 | grep wake > tx_queue_wake: 0 > tx0_wake: 0 Do they have a stop counter too? > > > > > In my opinion it makes the stop counter more useful, at little cost. > > > > > > > > > > > > > > > > --- > > > > > drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++-- > > > > > 1 file changed, 24 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > > index 3cb8aa193884..7e3c31ceaf7e 100644 > > > > > --- a/drivers/net/virtio_net.c > > > > > +++ b/drivers/net/virtio_net.c > > > > > @@ -88,6 +88,8 @@ struct virtnet_sq_stats { > > > > > u64_stats_t xdp_tx_drops; > > > > > u64_stats_t kicks; > > > > > u64_stats_t tx_timeouts; > > > > > + u64_stats_t tx_stop; > > > > > + u64_stats_t tx_wake; > > > > > }; > > > > > > > > > > struct virtnet_rq_stats { > > > > > @@ -112,6 +114,8 @@ static const struct virtnet_stat_desc > > > > virtnet_sq_stats_desc[] = { > > > > > { "xdp_tx_drops", VIRTNET_SQ_STAT(xdp_tx_drops) }, > > > > > { "kicks", VIRTNET_SQ_STAT(kicks) }, > > > > > { "tx_timeouts", VIRTNET_SQ_STAT(tx_timeouts) }, > > > > > + { "tx_stop", VIRTNET_SQ_STAT(tx_stop) }, > > > > > + { "tx_wake", VIRTNET_SQ_STAT(tx_wake) }, > > > > > }; > > > > > > > > > > static const struct virtnet_stat_desc virtnet_rq_stats_desc[] = { > > > > > @@ > > > > > -843,6 +847,9 @@ static void check_sq_full_and_disable(struct > > > > > virtnet_info > > > > *vi, > > > > > */ > > > > > if (sq->vq->num_free < 2+MAX_SKB_FRAGS) { > > > > > netif_stop_subqueue(dev, qnum); > > > > > + u64_stats_update_begin(&sq->stats.syncp); > > > > > + u64_stats_inc(&sq->stats.tx_stop); > > > > > + u64_stats_update_end(&sq->stats.syncp); > > > > > if (use_napi) { > > > > > if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) > > > > > virtqueue_napi_schedule(&sq->napi, sq- vq); > > @@ -851,6 +858,9 > > > > >@@ static void check_sq_full_and_disable(struct virtnet_info *vi, > > > > > free_old_xmit_skbs(sq, false); > > > > > if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { > > > > > netif_start_subqueue(dev, qnum); > > > > > + u64_stats_update_begin(&sq->stats.syncp); > > > > > + u64_stats_inc(&sq->stats.tx_wake); > > > > > + u64_stats_update_end(&sq->stats.syncp); > > > > > virtqueue_disable_cb(sq->vq); > > > > > } > > > > > } > > > > > @@ -2163,8 +2173,14 @@ static void virtnet_poll_cleantx(struct > > > > receive_queue *rq) > > > > > free_old_xmit_skbs(sq, true); > > > > > } while (unlikely(!virtqueue_enable_cb_delayed(sq->vq))); > > > > > > > > > > - if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > > > > > + if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) { > > > > > + if (netif_tx_queue_stopped(txq)) { > > > > > + u64_stats_update_begin(&sq->stats.syncp); > > > > > + u64_stats_inc(&sq->stats.tx_wake); > > > > > + u64_stats_update_end(&sq->stats.syncp); > > > > > + } > > > > > netif_tx_wake_queue(txq); > > > > > + } > > > > > > > > > > __netif_tx_unlock(txq); > > > > > } > > > > > @@ -2310,8 +2326,14 @@ static int virtnet_poll_tx(struct > > > > > napi_struct > > > > *napi, int budget) > > > > > virtqueue_disable_cb(sq->vq); > > > > > free_old_xmit_skbs(sq, true); > > > > > > > > > > - if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > > > > > + if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) { > > > > > + if (netif_tx_queue_stopped(txq)) { > > > > > + u64_stats_update_begin(&sq->stats.syncp); > > > > > + u64_stats_inc(&sq->stats.tx_wake); > > > > > + u64_stats_update_end(&sq->stats.syncp); > > > > > + } > > > > > netif_tx_wake_queue(txq); > > > > > + } > > > > > > > > > > opaque = virtqueue_enable_cb_prepare(sq->vq); > > > > > > > > > > -- > > > > > 2.42.0