[PATCH] virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq

Subsystems: networking drivers, the rest, virtio net driver

STALE1800d

5 messages, 2 authors, 2021-09-03 · open the first message on its own page

[PATCH] virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq

From: Li RongQing <hidden>
Date: 2021-08-26 08:31:05

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>
---
 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

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

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
---
 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

答复: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq

From: Li,Rongqing <hidden>
Date: 2021-08-31 02:09:43

-----邮件原件-----
发件人: Michael S. Tsirkin [off-list ref]
发送时间: 2021年8月31日 5:10
收件人: Li,Rongqing [off-list ref]
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:
quoted
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.

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

Re: 答复: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq

From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2021-08-31 14:34:13

On Tue, Aug 31, 2021 at 02:09:36AM +0000, Li,Rongqing wrote:
quoted
-----邮件原件-----
发件人: Michael S. Tsirkin [off-list ref]
发送时间: 2021年8月31日 5:10
收件人: Li,Rongqing [off-list ref]
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:
quoted
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.

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

答复: 答复: [PATCH] virtio_net: reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq

From: Li,Rongqing <hidden>
Date: 2021-09-03 04:00:08

-----邮件原件-----
发件人: Michael S. Tsirkin [off-list ref]
发送时间: 2021年8月31日 22:34
收件人: Li,Rongqing [off-list ref]
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:
quoted
quoted
-----邮件原件-----
发件人: Michael S. Tsirkin [off-list ref]
发送时间: 2021年8月31日 5:10
收件人: Li,Rongqing [off-list ref]
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:
quoted
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.

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

quoted
    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.
quoted
    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

quoted
-Li

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