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Tsirkin" Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, virtualization@lists.linux.dev, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com, dave.taht@gmail.com, kerneljasonxing@gmail.com, hengqi@linux.alibaba.com Subject: Re: [PATCH net-next v2] virtio_net: add support for Byte Queue Limits Message-ID: References: <20240612170851.1004604-1-jiri@resnulli.us> <20240617121234-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240617121234-mutt-send-email-mst@kernel.org> Mon, Jun 17, 2024 at 06:14:11PM CEST, mst@redhat.com wrote: >On Wed, Jun 12, 2024 at 07:08:51PM +0200, Jiri Pirko wrote: >> From: Jiri Pirko >> >> Add support for Byte Queue Limits (BQL). >> >> Tested on qemu emulated virtio_net device with 1, 2 and 4 queues. >> Tested with fq_codel and pfifo_fast. Super netperf with 50 threads is >> running in background. Netperf TCP_RR results: >> >> NOBQL FQC 1q: 159.56 159.33 158.50 154.31 agv: 157.925 >> NOBQL FQC 2q: 184.64 184.96 174.73 174.15 agv: 179.62 >> NOBQL FQC 4q: 994.46 441.96 416.50 499.56 agv: 588.12 >> NOBQL PFF 1q: 148.68 148.92 145.95 149.48 agv: 148.2575 >> NOBQL PFF 2q: 171.86 171.20 170.42 169.42 agv: 170.725 >> NOBQL PFF 4q: 1505.23 1137.23 2488.70 3507.99 agv: 2159.7875 >> BQL FQC 1q: 1332.80 1297.97 1351.41 1147.57 agv: 1282.4375 >> BQL FQC 2q: 768.30 817.72 864.43 974.40 agv: 856.2125 >> BQL FQC 4q: 945.66 942.68 878.51 822.82 agv: 897.4175 >> BQL PFF 1q: 149.69 151.49 149.40 147.47 agv: 149.5125 >> BQL PFF 2q: 2059.32 798.74 1844.12 381.80 agv: 1270.995 >> BQL PFF 4q: 1871.98 4420.02 4916.59 13268.16 agv: 6119.1875 >> >> Signed-off-by: Jiri Pirko >> --- >> v1->v2: >> - moved netdev_tx_completed_queue() call into __free_old_xmit(), >> propagate use_napi flag to __free_old_xmit() and only call >> netdev_tx_completed_queue() in case it is true >> - added forgotten call to netdev_tx_reset_queue() >> - fixed stats for xdp packets >> - fixed bql accounting when __free_old_xmit() is called from xdp path >> - handle the !use_napi case in start_xmit() kick section >> --- >> drivers/net/virtio_net.c | 50 +++++++++++++++++++++++++--------------- >> 1 file changed, 32 insertions(+), 18 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 61a57d134544..5863c663ccab 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -84,7 +84,9 @@ struct virtnet_stat_desc { >> >> struct virtnet_sq_free_stats { >> u64 packets; >> + u64 xdp_packets; >> u64 bytes; >> + u64 xdp_bytes; >> }; >> >> struct virtnet_sq_stats { >> @@ -506,29 +508,33 @@ static struct xdp_frame *ptr_to_xdp(void *ptr) >> return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG); >> } >> >> -static void __free_old_xmit(struct send_queue *sq, bool in_napi, >> +static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq, >> + bool in_napi, bool use_napi, >> struct virtnet_sq_free_stats *stats) >> { >> unsigned int len; >> void *ptr; >> >> while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) { >> - ++stats->packets; >> - >> if (!is_xdp_frame(ptr)) { >> struct sk_buff *skb = ptr; >> >> pr_debug("Sent skb %p\n", skb); >> >> + stats->packets++; >> stats->bytes += skb->len; >> napi_consume_skb(skb, in_napi); >> } else { >> struct xdp_frame *frame = ptr_to_xdp(ptr); >> >> - stats->bytes += xdp_get_frame_len(frame); >> + stats->xdp_packets++; >> + stats->xdp_bytes += xdp_get_frame_len(frame); >> xdp_return_frame(frame); >> } >> } >> + if (use_napi) >> + netdev_tx_completed_queue(txq, stats->packets, stats->bytes); >> + >> } >> >> /* Converting between virtqueue no. and kernel tx/rx queue no. >> @@ -955,21 +961,22 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf) >> virtnet_rq_free_buf(vi, rq, buf); >> } >> >> -static void free_old_xmit(struct send_queue *sq, bool in_napi) >> +static void free_old_xmit(struct send_queue *sq, struct netdev_queue *txq, >> + bool in_napi, bool use_napi) >> { >> struct virtnet_sq_free_stats stats = {0}; >> >> - __free_old_xmit(sq, in_napi, &stats); >> + __free_old_xmit(sq, txq, in_napi, use_napi, &stats); >> >> /* Avoid overhead when no packets have been processed >> * happens when called speculatively from start_xmit. >> */ >> - if (!stats.packets) >> + if (!stats.packets && !stats.xdp_packets) >> return; >> >> u64_stats_update_begin(&sq->stats.syncp); >> - u64_stats_add(&sq->stats.bytes, stats.bytes); >> - u64_stats_add(&sq->stats.packets, stats.packets); >> + u64_stats_add(&sq->stats.bytes, stats.bytes + stats.xdp_bytes); >> + u64_stats_add(&sq->stats.packets, stats.packets + stats.xdp_packets); >> u64_stats_update_end(&sq->stats.syncp); >> } >> >> @@ -1003,7 +1010,9 @@ static void check_sq_full_and_disable(struct virtnet_info *vi, >> * early means 16 slots are typically wasted. >> */ >> if (sq->vq->num_free < 2+MAX_SKB_FRAGS) { >> - netif_stop_subqueue(dev, qnum); >> + struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); >> + >> + netif_tx_stop_queue(txq); >> u64_stats_update_begin(&sq->stats.syncp); >> u64_stats_inc(&sq->stats.stop); >> u64_stats_update_end(&sq->stats.syncp); >> @@ -1012,7 +1021,7 @@ static void check_sq_full_and_disable(struct virtnet_info *vi, >> virtqueue_napi_schedule(&sq->napi, sq->vq); >> } else if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { >> /* More just got used, free them then recheck. */ >> - free_old_xmit(sq, false); >> + free_old_xmit(sq, txq, false, use_napi); >> if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { >> netif_start_subqueue(dev, qnum); >> u64_stats_update_begin(&sq->stats.syncp); >> @@ -1138,7 +1147,8 @@ static int virtnet_xdp_xmit(struct net_device *dev, >> } >> >> /* Free up any pending old buffers before queueing new ones. */ >> - __free_old_xmit(sq, false, &stats); >> + __free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq), >> + false, sq->napi.weight, &stats); > > >So what happens if sq->napi.weight changes while packet is in the queue? >What prevents that? Sigh. You are correct. That is what Jason points out as well. > > > >> >> for (i = 0; i < n; i++) { >> struct xdp_frame *xdpf = frames[i]; >> @@ -2313,7 +2323,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) >> >> do { >> virtqueue_disable_cb(sq->vq); >> - free_old_xmit(sq, true); >> + free_old_xmit(sq, txq, true, true); >> } while (unlikely(!virtqueue_enable_cb_delayed(sq->vq))); >> >> if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) { >> @@ -2412,6 +2422,7 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index) >> goto err_xdp_reg_mem_model; >> >> virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi); >> + netdev_tx_reset_queue(netdev_get_tx_queue(vi->dev, qp_index)); >> virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi); >> >> return 0; >> @@ -2471,7 +2482,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) >> txq = netdev_get_tx_queue(vi->dev, index); >> __netif_tx_lock(txq, raw_smp_processor_id()); >> virtqueue_disable_cb(sq->vq); >> - free_old_xmit(sq, true); >> + free_old_xmit(sq, txq, true, true); >> >> if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) { >> if (netif_tx_queue_stopped(txq)) { >> @@ -2559,17 +2570,18 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >> struct send_queue *sq = &vi->sq[qnum]; >> int err; >> struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); >> - bool kick = !netdev_xmit_more(); >> + bool xmit_more = netdev_xmit_more(); >> bool use_napi = sq->napi.weight; >> + bool kick; >> >> /* Free up any pending old buffers before queueing new ones. */ >> do { >> if (use_napi) >> virtqueue_disable_cb(sq->vq); >> >> - free_old_xmit(sq, false); >> + free_old_xmit(sq, txq, false, use_napi); >> >> - } while (use_napi && kick && >> + } while (use_napi && !xmit_more && >> unlikely(!virtqueue_enable_cb_delayed(sq->vq))); >> >> /* timestamp packet in software */ >> @@ -2598,7 +2610,9 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >> >> check_sq_full_and_disable(vi, dev, sq); >> >> - if (kick || netif_xmit_stopped(txq)) { >> + kick = use_napi ? __netdev_tx_sent_queue(txq, skb->len, xmit_more) : >> + !xmit_more && netif_xmit_stopped(txq); >> + if (kick) { >> if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) { >> u64_stats_update_begin(&sq->stats.syncp); >> u64_stats_inc(&sq->stats.kicks); >> -- >> 2.45.1 >