Michael S. Tsirkin
2023-Apr-27 08:12 UTC
[PATCH] virtio_net: suppress cpu stall when free_unused_bufs
On Thu, Apr 27, 2023 at 03:13:44PM +0800, Xuan Zhuo wrote:> On Thu, 27 Apr 2023 15:02:26 +0800, Wenliang Wang <wangwenliang.1995 at bytedance.com> wrote: > > > > > > On 4/27/23 2:20 PM, Xuan Zhuo wrote: > > > On Thu, 27 Apr 2023 12:34:33 +0800, Wenliang Wang <wangwenliang.1995 at bytedance.com> wrote: > > >> For multi-queue and large rx-ring-size use case, the following error > > > > > > Cound you give we one number for example? > > > > 128 queues and 16K queue_size is typical. > > > > > > > >> occurred when free_unused_bufs: > > >> rcu: INFO: rcu_sched self-detected stall on CPU. > > >> > > >> Signed-off-by: Wenliang Wang <wangwenliang.1995 at bytedance.com> > > >> --- > > >> drivers/net/virtio_net.c | 1 + > > >> 1 file changed, 1 insertion(+) > > >> > > >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > >> index ea1bd4bb326d..21d8382fd2c7 100644 > > >> --- a/drivers/net/virtio_net.c > > >> +++ b/drivers/net/virtio_net.c > > >> @@ -3565,6 +3565,7 @@ static void free_unused_bufs(struct virtnet_info *vi) > > >> struct virtqueue *vq = vi->rq[i].vq; > > >> while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > >> virtnet_rq_free_unused_buf(vq, buf); > > >> + schedule(); > > > > > > Just for rq? > > > > > > Do we need to do the same thing for sq? > > Rq buffers are pre-allocated, take seconds to free rq unused buffers. > > > > Sq unused buffers are much less, so do the same for sq is optional. > > I got. > > I think we should look for a way, compatible with the less queues or the smaller > rings. Calling schedule() directly may be not a good way. > > Thanks.Why isn't it a good way?> > > > > > > > > Thanks. > > > > > > > > >> } > > >> } > > >> > > >> -- > > >> 2.20.1 > > >>
Xuan Zhuo
2023-Apr-27 08:13 UTC
[PATCH] virtio_net: suppress cpu stall when free_unused_bufs
On Thu, 27 Apr 2023 04:12:44 -0400, "Michael S. Tsirkin" <mst at redhat.com> wrote:> On Thu, Apr 27, 2023 at 03:13:44PM +0800, Xuan Zhuo wrote: > > On Thu, 27 Apr 2023 15:02:26 +0800, Wenliang Wang <wangwenliang.1995 at bytedance.com> wrote: > > > > > > > > > On 4/27/23 2:20 PM, Xuan Zhuo wrote: > > > > On Thu, 27 Apr 2023 12:34:33 +0800, Wenliang Wang <wangwenliang.1995 at bytedance.com> wrote: > > > >> For multi-queue and large rx-ring-size use case, the following error > > > > > > > > Cound you give we one number for example? > > > > > > 128 queues and 16K queue_size is typical. > > > > > > > > > > >> occurred when free_unused_bufs: > > > >> rcu: INFO: rcu_sched self-detected stall on CPU. > > > >> > > > >> Signed-off-by: Wenliang Wang <wangwenliang.1995 at bytedance.com> > > > >> --- > > > >> drivers/net/virtio_net.c | 1 + > > > >> 1 file changed, 1 insertion(+) > > > >> > > > >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > >> index ea1bd4bb326d..21d8382fd2c7 100644 > > > >> --- a/drivers/net/virtio_net.c > > > >> +++ b/drivers/net/virtio_net.c > > > >> @@ -3565,6 +3565,7 @@ static void free_unused_bufs(struct virtnet_info *vi) > > > >> struct virtqueue *vq = vi->rq[i].vq; > > > >> while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > > >> virtnet_rq_free_unused_buf(vq, buf); > > > >> + schedule(); > > > > > > > > Just for rq? > > > > > > > > Do we need to do the same thing for sq? > > > Rq buffers are pre-allocated, take seconds to free rq unused buffers. > > > > > > Sq unused buffers are much less, so do the same for sq is optional. > > > > I got. > > > > I think we should look for a way, compatible with the less queues or the smaller > > rings. Calling schedule() directly may be not a good way. > > > > Thanks. > > Why isn't it a good way?For the small ring, I don't think it is a good way, maybe we only deal with one buf, then call schedule(). We can call the schedule() after processing a certain number of buffers, or check need_resched () first. Thanks.> > > > > > > > > > > > > > Thanks. > > > > > > > > > > > >> } > > > >> } > > > >> > > > >> -- > > > >> 2.20.1 > > > >> >