Re: [PATCH net-next v2 2/2] net: sched: Lockless Token Bucket (LTB) qdisc

[YU, Xiangning]

On 7/8/20 5:08 PM, Eric Dumazet wrote:
> 
> 
> On 7/8/20 4:59 PM, YU, Xiangning wrote:
> 
>>
>> Yes, we are touching a cache line here to make sure aggregation tasklet is 
>> scheduled immediately. In most cases it is a call to test_and_set_bit(). 
> 
> 
> test_and_set_bit() is dirtying the cache line even if the bit is already set.
> 

Yes. I do hope we can avoid this.

>>
>> We might be able to do some inline processing without tasklet here, still we 
>> need to make sure the aggregation won't run simultaneously on multiple CPUs. 
> 
> I am actually surprised you can reach 8 Mpps with so many cache line bouncing 
> around.
> 
> If you replace the ltb qdisc with standard mq+pfifo_fast, what kind of 
> throughput do you get ?
> 

Just tried it using pktgen, we are far from baseline. I can get 13Mpps with 10 
threads in my test setup.

Thanks,
- Xiangning