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

[Shreyansh Jain <shreyansh.jain@nxp.com>]

Hi Konstantin, Ruifeng,

> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> Sent: Monday, April 8, 2019 3:00 PM
> To: Ruifeng Wang (Arm Technology China) <Ruifeng.Wang@arm.com>;
> Shreyansh Jain <shreyansh.jain@nxp.com>; dev@dpdk.org
> Cc: nd <nd@arm.com>
> Subject: RE: [dpdk-dev] [PATCH] examples/l3fwd: support separate buffer
> pool per port
> 
> 
> 
> >
> > 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.

> 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
> >

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