Re: [PATCH bpf-next v2 06/10] xsk: propagate napi_id to XDP socket Rx path

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 2020-11-16 13:42, Michael S. Tsirkin wrote:
On Mon, Nov 16, 2020 at 01:01:40PM +0100, Björn Töpel wrote:

On 2020-11-16 12:55, Michael S. Tsirkin wrote:
On Mon, Nov 16, 2020 at 12:04:12PM +0100, BjÃf¶rn TÃf¶pel wrote:
From: BjÃf¶rn TÃf¶pel <bjorn.topel@xxxxxxxxx>

Add napi_id to the xdp_rxq_info structure, and make sure the XDP
socket pick up the napi_id in the Rx path. The napi_id is used to find
the corresponding NAPI structure for socket busy polling.

Acked-by: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx>
Signed-off-by: BjÃf¶rn TÃf¶pel <bjorn.topel@xxxxxxxxx>

A bunch of drivers just pass in 0. could you explain when
is that ok? how bad is it if the wrong id is used?


If zero is passed, which is a non-valid NAPI_ID, busy-polling will never
be performed.

Depending on the structure of the driver, napi might or might not be
initialized (napi_id != 0) or even available. When it wasn't obvious, I
simply set it to zero.

So, short; No harm if zero, but busy-polling cannot be used in an XDP
context.


[...]
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 21b71148c532..d71fe41595b7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1485,7 +1485,7 @@ static int virtnet_open(struct net_device *dev)
   			if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
   				schedule_delayed_work(&vi->refill, 0);
-		err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i);
+		err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, 0);
   		if (err < 0)
   			return err;

Should this be rq.napi.napi_id ?


Yes, if rq.napi.napi_id is valid here! Is it?

What initializes it? netif_napi_add? Then I think yes, it's
initialized for all queues ...
Needs to be tested naturally.


Yeah, netid_napi_add does the id generation.

My idea was that driver would gradually move to a correct NAPI id (given
that it's hard to test w/o HW. Virtio however is simpler to test. :-)


Björn



[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux