Re: [PATCH] virtio_net: suppress cpu stall when free_unused_bufs
From: Wenliang Wang
Date: Thu Apr 27 2023 - 04:50:36 EST
On 4/27/23 4:23 PM, Michael S. Tsirkin wrote:
On Thu, Apr 27, 2023 at 04:13:45PM +0800, Xuan Zhuo wrote:
On Thu, 27 Apr 2023 04:12:44 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> 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@xxxxxxxxxxxxx> wrote:
On 4/27/23 2:20 PM, Xuan Zhuo wrote:
On Thu, 27 Apr 2023 12:34:33 +0800, Wenliang Wang <wangwenliang.1995@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
---
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.
Wenliang, does
if (need_resched())
schedule();
fix the issue for you?
Yeah, it works better.
Thanks.
}
}
--
2.20.1