Re: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2021-08-30 21:10:25
Also in:
bpf, virtualization
On Thu, Aug 26, 2021 at 04:21:35PM +0800, Li RongQing wrote:
smp_processor_id()/raw* will be called once each when not more queues in virtnet_xdp_get_sq() which is called in non-preemptible context, so it's safe to call the function smp_processor_id() once. Signed-off-by: Li RongQing <redacted>
commit log should probably explain why it's a good idea to replace raw_smp_processor_id with smp_processor_id in the case of curr_queue_pairs <= nr_cpu_ids.
quoted hunk ↗ jump to hunk
--- drivers/net/virtio_net.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 2e42210a6503..2a7b368c1da2 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c@@ -528,19 +528,20 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi, * functions to perfectly solve these three problems at the same time. */ #define virtnet_xdp_get_sq(vi) ({ \ + int cpu = smp_processor_id(); \ struct netdev_queue *txq; \ typeof(vi) v = (vi); \ unsigned int qp; \ \ if (v->curr_queue_pairs > nr_cpu_ids) { \ qp = v->curr_queue_pairs - v->xdp_queue_pairs; \ - qp += smp_processor_id(); \ + qp += cpu; \ txq = netdev_get_tx_queue(v->dev, qp); \ __netif_tx_acquire(txq); \ } else { \ - qp = smp_processor_id() % v->curr_queue_pairs; \ + qp = cpu % v->curr_queue_pairs; \ txq = netdev_get_tx_queue(v->dev, qp); \ - __netif_tx_lock(txq, raw_smp_processor_id()); \ + __netif_tx_lock(txq, cpu); \ } \ v->sq + qp; \ })-- 2.33.0.69.gc420321.dirty