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.
