[dpdk-dev] [PATCH] examples/l3fwd: support separate buffer pool per port

[Ananyev, Konstantin]

Hi Shreyansh,

> > > I tried this patch on MacchiatoBin + 82599 NIC.
> > > Compared with global-pool mode, per-port-pool mode showed slightly
> > lower performance in single core test.
> >
> > That was my thought too - for the case when queues from multiple ports
> > are handled by the same core
> > it probably would only slowdown things.
> 
> Thanks for your comments.
> 
> This is applicable for cases where separate cores can handle separate ports - each with their pools. (somehow I felt that message in commit
> was adequate - I can rephrase if that is misleading)
> 
> In case there is enough number of cores available for datapath, such segregation can result in better performance - possibly because of
> drop in pool and cache conflicts.
> At least on some of NXP SoC, this resulted in over 15% improvement.
> And, in other cases it didn't lead to any drop/negative-impact.

If each core manages just one port, then yes definitely performance increase is expected.
If that's the case you'd like enable, then can I suggest to have mempool per lcore not per port?
I think it would be plausible for both cases:
- one port per core (your case).
- multiple ports per core.   
Konstantin

> 
> > Wonder what is the use case for the patch and what is the performance
> > gain you observed?
> 
> For hardware backed pools, hardware access and exclusion are expensive. By segregating pool/port/lcores it is possible to attain a conflict
> free path. This is the use-case this patch targets.
> And anyways, this is an optional feature.
> 
> > Konstantin
> >
> > > In dual core test, both modes had nearly same performance.
> 
> OK
> 
> > >
> > > My setup only has two ports which is limited.
> > > Just want to know the per-port-pool mode has more performance gain
> > when many ports are bound to  different cores?
> 
> Yes, though not necessarily *many* - in my case, I had 4 ports and even then about ~10% improvement was directly visible. I increased the
> port count and I was able to touch about ~15%. I did pin each port to a separate core, though.
> But again, important point is that without this feature enabled, I didn't see any drop in performance. Did you observe any drop?
> 
> > >
> > > Used commands:
> > > sudo ./examples/l3fwd/build/l3fwd -c 0x4 -w 0000:01:00.0 -w
> > 0000:01:00.1 -- -P -p 3 --config='(0,0,2),(1,0,2)' --per-port-pool
> > > sudo ./examples/l3fwd/build/l3fwd -c 0xc -w 0000:01:00.0 -w
> > 0000:01:00.1 -- -P -p 3 --config='(0,0,2),(1,0,3)' --per-port-pool
> > >
> > > Regards,
> > > /Ruifeng
> > >
> 
> [...]