On Wed, Jun 5, 2024 at 7:51 PM Heng Qi <hengqi@xxxxxxxxxxxxxxxxx> wrote: > > On Wed, 5 Jun 2024 13:30:51 +0200, Jiri Pirko <jiri@xxxxxxxxxxx> wrote: > > Mon, May 20, 2024 at 02:48:15PM CEST, jiri@xxxxxxxxxxx wrote: > > >Fri, May 10, 2024 at 09:11:16AM CEST, hengqi@xxxxxxxxxxxxxxxxx wrote: > > >>On Thu, 9 May 2024 13:46:15 +0200, Jiri Pirko <jiri@xxxxxxxxxxx> wrote: > > >>> From: Jiri Pirko <jiri@xxxxxxxxxx> > > >>> > > >>> Add support for Byte Queue Limits (BQL). > > >> > > >>Historically both Jason and Michael have attempted to support BQL > > >>for virtio-net, for example: > > >> > > >>https://lore.kernel.org/netdev/21384cb5-99a6-7431-1039-b356521e1bc3@xxxxxxxxxx/ > > >> > > >>These discussions focus primarily on: > > >> > > >>1. BQL is based on napi tx. Therefore, the transfer of statistical information > > >>needs to rely on the judgment of use_napi. When the napi mode is switched to > > >>orphan, some statistical information will be lost, resulting in temporary > > >>inaccuracy in BQL. > > >> > > >>2. If tx dim is supported, orphan mode may be removed and tx irq will be more > > >>reasonable. This provides good support for BQL. > > > > > >But when the device does not support dim, the orphan mode is still > > >needed, isn't it? > > > > Heng, is my assuption correct here? Thanks! > > > > Maybe, according to our cloud data, napi_tx=on works better than orphan mode in > most scenarios. Although orphan mode performs better in specific benckmark, For example pktgen (I meant even if the orphan mode can break pktgen, it can finish when there's a new packet that needs to be sent after pktgen is completed). > perf of napi_tx can be enhanced through tx dim. Then, there is no reason not to > support dim for devices that want the best performance. Ideally, if we can drop orphan mode, everything would be simplified. > > Back to this patch set, I think BQL as a point that affects performance should > deserve more comprehensive test data. Thanks > > Thanks. > > > > > > >> > > >>Thanks. > > >> > > >>> > > >>> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx> > > >>> --- > > >>> drivers/net/virtio_net.c | 33 ++++++++++++++++++++------------- > > >>> 1 file changed, 20 insertions(+), 13 deletions(-) > > >>> > > >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > >>> index 218a446c4c27..c53d6dc6d332 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 { > > >>> @@ -512,19 +514,19 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi, > > >>> 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); > > >>> } > > >>> } > > >>> @@ -965,7 +967,8 @@ 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) > > >>> { > > >>> struct virtnet_sq_free_stats stats = {0}; > > >>> > > >>> @@ -974,9 +977,11 @@ static void free_old_xmit(struct send_queue *sq, bool in_napi) > > >>> /* 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; > > >>> > > >>> + netdev_tx_completed_queue(txq, stats.packets, stats.bytes); > > >>> + > > >>> u64_stats_update_begin(&sq->stats.syncp); > > >>> u64_stats_add(&sq->stats.bytes, stats.bytes); > > >>> u64_stats_add(&sq->stats.packets, stats.packets); > > >>> @@ -1013,13 +1018,15 @@ 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); > > >>> if (use_napi) { > > >>> if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) > > >>> 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); > > >>> if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { > > >>> netif_start_subqueue(dev, qnum); > > >>> virtqueue_disable_cb(sq->vq); > > >>> @@ -2319,7 +2326,7 @@ 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); > > >>> } while (unlikely(!virtqueue_enable_cb_delayed(sq->vq))); > > >>> > > >>> if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > > >>> @@ -2471,7 +2478,7 @@ 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); > > >>> > > >>> if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > > >>> netif_tx_wake_queue(txq); > > >>> @@ -2553,7 +2560,7 @@ 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; > > >>> > > >>> /* Free up any pending old buffers before queueing new ones. */ > > >>> @@ -2561,9 +2568,9 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > > >>> if (use_napi) > > >>> virtqueue_disable_cb(sq->vq); > > >>> > > >>> - free_old_xmit(sq, false); > > >>> + free_old_xmit(sq, txq, false); > > >>> > > >>> - } while (use_napi && kick && > > >>> + } while (use_napi && !xmit_more && > > >>> unlikely(!virtqueue_enable_cb_delayed(sq->vq))); > > >>> > > >>> /* timestamp packet in software */ > > >>> @@ -2592,7 +2599,7 @@ 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)) { > > >>> + if (__netdev_tx_sent_queue(txq, skb->len, xmit_more)) { > > >>> if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) { > > >>> u64_stats_update_begin(&sq->stats.syncp); > > >>> u64_stats_inc(&sq->stats.kicks); > > >>> -- > > >>> 2.44.0 > > >>> > > >>> >
