26/06/2025 16:29, Stephen Hemminger:
> On Thu, 26 Jun 2025 13:18:18 +0000
> Bing Zhao <bi...@nvidia.com> wrote:
> 
> > Hi Stephen,
> > 
> > Thanks for your review and comments. I will add the description about the 
> > new devarg in our mlx5.rst file to have a detailed description.
> > Indeed, after some review and internal call discussion with our datapath 
> > experts. We would like to change the devarg a little bit but not only 0 / 1 
> > as a chicken bit.
> > 
> > Since the memory accessing footprints and orders may impact the 
> > performance. In the perf test, we found that the alignment of the queue 
> > address may impact it. The basic starting address alignment is system page 
> > size, but it can be bigger.
> > So the new devarg use will be the log value of the alignment for all 
> > queues’ starting addresses. And on different CPU architectures / 
> > generations that have different LLC systems can try to use different 
> > alignment to get the best performance without rebuilding the binary 
> > application from the source code and it is configurable. WDYT?
> 
> Please make it automatic, the driver already has too many config bits.
> The users should just get good performance with the default.
> If driver needs to it should look at any/all system info to determine what 
> the best setting is.

The default would be good enough, but it looks very difficult to know the best 
value.
That's why the idea is to allow some tuning here.

I agree there are too many devargs for most users,
but at the same time DPDK is a project to get the best performance,
that's why there are so many tuning possible.
I think we can meet both goals by making clear which options are for advanced 
tuning,
so a basic user will not mess with with such options which have a good default 
by the way.


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