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

-----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

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