On 2026/6/15 10:48 Xuan Zhuo <[email protected]> write: > On Thu, 11 Jun 2026 10:56:43 +0800, [email protected] wrote: > > From: Menglong Dong <[email protected]> > > > > During packet receiving in virtio-net, the rq can be empty, which means > > "rq->vq->num_free == virtqueue_get_vring_size(rq->vq)", in > > virtnet_add_recvbuf_xsk(), if we are using xsk. Meanwhile, the fill ring > > can be empty too, which means we can't allocate anything from > > xsk_buff_alloc_batch(). Then, we will set the XDP_RING_NEED_WAKEUP flag. > > [...] > > > > + need_wakeup = xsk_uses_need_wakeup(pool); > > xsk_buffs = rq->xsk_buffs; > > > > + /* If both rq->vq and fill ring are empty, and then the user submit > > + * all the chunks to the fill ring and check the wake up flag > > + * after xsk_buff_alloc_batch() and before xsk_set_rx_need_wakeup(), > > + * we will lose the chance to wake up the rx napi, so we have to > > + * set the need_wakeup flag here. > > + */ > > + if (need_wakeup && virtqueue_get_vring_size(rq->vq) == rq->vq->num_free) > > + xsk_set_rx_need_wakeup(pool); > > Is Condition A here too strict? We should trigger the wakeup under a wider > range > of scenarios.
Hi, Xuan. Thinks for your reviewing :) The logic here is a addition logic to the origin wake up logic, which I planed to fix a race condition. However, this race condition seems not likely to happen, as we discussed in this thread: https://lore.kernel.org/netdev/[email protected]/ So this patch is not necessary, and I'll send the 2nd patch standalone. Thanks! Menglong Dong > > > + > > num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free); > > if (!num) { > > - if (xsk_uses_need_wakeup(pool)) { > > + if (need_wakeup) { > > xsk_set_rx_need_wakeup(pool); > > /* Return 0 instead of -ENOMEM so that NAPI is > > * descheduled. > > @@ -1341,8 +1352,6 @@ static int virtnet_add_recvbuf_xsk(struct > > virtnet_info *vi, struct receive_queue > > } > > > > return -ENOMEM; > > - } else { > > - xsk_clear_rx_need_wakeup(pool); > > } > > > > len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len; > > @@ -1363,6 +1372,16 @@ static int virtnet_add_recvbuf_xsk(struct > > virtnet_info *vi, struct receive_queue > > goto err; > > } > > > > + if (need_wakeup) { > > + if (rq->vq->num_free) > > + /* We have free buffers, so we'd better wake up the > > + * rx napi as soon as possible. > > + */ > > + xsk_set_rx_need_wakeup(pool); > > Is the purpose of waking up RX NAPI to invoke try_fill_recv? However, > virtnet_poll does not call try_fill_recv directly. it is done > conditionally. > > Thanks. > > > > + else > > + xsk_clear_rx_need_wakeup(pool); > > + } > > + > > return num; > > > > err: > > -- > > 2.54.0 > > > >
