| Message ID | 1629966095-16341-1-git-send-email-lirongqing@baidu.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq | expand |
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 <lirongqing@baidu.com> 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. > --- > 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 > >
> -----邮件原件----- > 发件人: Michael S. Tsirkin <mst@redhat.com> > 发送时间: 2021年8月31日 5:10 > 收件人: Li,Rongqing <lirongqing@baidu.com> > 抄送: netdev@vger.kernel.org; bpf@vger.kernel.org; > virtualization@lists.linux-foundation.org > 主题: Re: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in > virtnet_xdp_get_sq > > 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 <lirongqing@baidu.com> > > 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. > I change it as below, is it ok? virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq smp_processor_id() and raw_smp_processor_id() are called once each in virtnet_xdp_get_sq(), when curr_queue_pairs <= nr_cpu_ids, should be merged virtnet_xdp_get_sq() is called in non-preemptible context, so it's safe to call the function smp_processor_id(), and keep smp_processor_id(), and remove the calling of raw_smp_processor_id(), avoid the wrong use virtnet_xdp_get_sq to preemptible context in the future -Li
On Tue, Aug 31, 2021 at 02:09:36AM +0000, Li,Rongqing wrote: > > -----邮件原件----- > > 发件人: Michael S. Tsirkin <mst@redhat.com> > > 发送时间: 2021年8月31日 5:10 > > 收件人: Li,Rongqing <lirongqing@baidu.com> > > 抄送: netdev@vger.kernel.org; bpf@vger.kernel.org; > > virtualization@lists.linux-foundation.org > > 主题: Re: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in > > virtnet_xdp_get_sq > > > > 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 <lirongqing@baidu.com> > > > > 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. > > > > > I change it as below, is it ok? > > virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq shorter: virtio_net: s/raw_smp_processor_id/smp_processor_id/ in virtnet_xdp_get_sq > > smp_processor_id() and raw_smp_processor_id() are called once > each in virtnet_xdp_get_sq(), when curr_queue_pairs <= nr_cpu_ids, > should be merged I'd just drop this part. > > virtnet_xdp_get_sq() is called in non-preemptible context, so > it's safe to call the function smp_processor_id(), and keep > smp_processor_id(), and remove the calling of raw_smp_processor_id(), > avoid the wrong use virtnet_xdp_get_sq to preemptible context > in the future s/avoid.*/this way we'll get a warning if this is ever called in a preemptible context/ > > -Li
> -----邮件原件----- > 发件人: Michael S. Tsirkin <mst@redhat.com> > 发送时间: 2021年8月31日 22:34 > 收件人: Li,Rongqing <lirongqing@baidu.com> > 抄送: netdev@vger.kernel.org; bpf@vger.kernel.org; > virtualization@lists.linux-foundation.org > 主题: Re: 答复: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in > virtnet_xdp_get_sq > > On Tue, Aug 31, 2021 at 02:09:36AM +0000, Li,Rongqing wrote: > > > -----邮件原件----- > > > 发件人: Michael S. Tsirkin <mst@redhat.com> > > > 发送时间: 2021年8月31日 5:10 > > > 收件人: Li,Rongqing <lirongqing@baidu.com> > > > 抄送: netdev@vger.kernel.org; bpf@vger.kernel.org; > > > virtualization@lists.linux-foundation.org > > > 主题: Re: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in > > > virtnet_xdp_get_sq > > > > > > 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 <lirongqing@baidu.com> > > > > > > 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. > > > > > > > > > I change it as below, is it ok? > > > > virtio_net: reduce raw_smp_processor_id() calling in > > virtnet_xdp_get_sq > > shorter: > > virtio_net: s/raw_smp_processor_id/smp_processor_id/ in virtnet_xdp_get_sq > > > > > > smp_processor_id() and raw_smp_processor_id() are called once > > each in virtnet_xdp_get_sq(), when curr_queue_pairs <= nr_cpu_ids, > > should be merged > > I'd just drop this part. > > > > > virtnet_xdp_get_sq() is called in non-preemptible context, so > > it's safe to call the function smp_processor_id(), and keep > > smp_processor_id(), and remove the calling of raw_smp_processor_id(), > > avoid the wrong use virtnet_xdp_get_sq to preemptible context > > in the future > > s/avoid.*/this way we'll get a warning if this is ever called in a preemptible > context/ > Thanks, should I resend it -Li > > > > > -Li
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; \ })
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 <lirongqing@baidu.com> --- drivers/net/virtio_net.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)