Re: [Linuxarm] [PATCH net] net: sched: fix packet stuck problem for lockless qdisc

On 2021/3/20 3:45, Cong Wang wrote:

On Fri, Mar 19, 2021 at 2:25 AM Yunsheng Lin [off-list ref] wrote:

quoted

I had done some performance test to see if there is value to
fix the packet stuck problem and support lockless qdisc bypass,
here is some result using pktgen in 'queue_xmit' mode on a dummy
device as Paolo Abeni had done in [1], and using pfifo_fast qdisc:

threads  vanilla    locked-qdisc    vanilla+this_patch
   1     2.6Mpps      2.9Mpps            2.5Mpps
   2     3.9Mpps      4.8Mpps            3.6Mpps
   4     5.6Mpps      3.0Mpps            4.7Mpps
   8     2.7Mpps      1.6Mpps            2.8Mpps
   16    2.2Mpps      1.3Mpps            2.3Mpps

locked-qdisc: test by removing the "TCQ_F_NOLOCK | TCQ_F_CPUSTATS".

I read this as this patch introduces somehow a performance
regression for -net, as the lockless bypass patch you submitted is
for -net-next.

Yes, right now there is performance regression for fixing this bug,
but the problem is that if we can not fix the above data race without
any performance regression, do you prefer to send this patch to
-net, or to -net-next with the lockless bypass patch?

Any idea to fix this with less performance regression?

Thanks.

.