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Tsirkin" To: Jiri Pirko 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 v3] virtio_net: add support for Byte Queue Limits Message-ID: <20240619041846-mutt-send-email-mst@kernel.org> References: <20240618144456.1688998-1-jiri@resnulli.us> <20240618140326-mutt-send-email-mst@kernel.org> <20240619014938-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 Wed, Jun 19, 2024 at 10:05:41AM +0200, Jiri Pirko wrote: > >Oh. Right of course. Worth a comment maybe? Just to make sure > >we remember not to call __free_old_xmit twice in a row > >without reinitializing stats. > >Or move the initialization into __free_old_xmit to make it > >self-contained .. > > Well, the initialization happens in the caller by {0}, Wouldn't > memset in __free_old_xmit() add an extra overhead? IDK. Well if I did the below the binary is a bit smaller. If you have to respin you can include it. If not I can submit separately. ---- virtio-net: cleanup __free_old_xmit Two call sites of __free_old_xmit zero-initialize stats, doing it inside __free_old_xmit seems to make compiler's job a bit easier: $ size /tmp/orig/virtio_net.o text data bss dec hex filename 65857 3892 100 69849 110d9 /tmp/orig/virtio_net.o $ size /tmp/new/virtio_net.o text data bss dec hex filename 65760 3892 100 69752 11078 /tmp/new/virtio_net.o Couldn't measure any performance impact, unsurprizingly. Signed-off-by: Michael S. Tsirkin --- diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 283b34d50296..c2ce8de340f7 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -383,6 +383,8 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi, unsigned int len; void *ptr; + stats->bytes = stats->packets = 0; + while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) { ++stats->packets; @@ -828,7 +830,7 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf) static void free_old_xmit(struct send_queue *sq, bool in_napi) { - struct virtnet_sq_free_stats stats = {0}; + struct virtnet_sq_free_stats stats; __free_old_xmit(sq, in_napi, &stats); @@ -979,7 +981,7 @@ static int virtnet_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames, u32 flags) { struct virtnet_info *vi = netdev_priv(dev); - struct virtnet_sq_free_stats stats = {0}; + struct virtnet_sq_free_stats stats; struct receive_queue *rq = vi->rq; struct bpf_prog *xdp_prog; struct send_queue *sq;