On 31/01/2024 14:29, David Hildenbrand wrote: >>> Note that regarding NUMA effects, I mean when some memory access within the same >>> socket is faster/slower even with only a single node. On AMD EPYC that's >>> possible, depending on which core you are running and on which memory controller >>> the memory you want to access is located. If both are in different quadrants >>> IIUC, the access latency will be different. >> >> I've configured the NUMA to only bring the RAM and CPUs for a single socket >> online, so I shouldn't be seeing any of these effects. Anyway, I've been using >> the Altra as a secondary because its so much slower than the M2. Let me move >> over to it and see if everything looks more straightforward there. > > Better use a system where people will actually run Linux production workloads > on, even if it is slower :) > > [...] > >>>> >>>> I'll continue to mess around with it until the end of the day. But I'm not >>>> making any headway, then I'll change tack; I'll just measure the performance of >>>> my contpte changes using your fork/zap stuff as the baseline and post based on >>>> that. >>> >>> You should likely not focus on M2 results. Just pick a representative bare metal >>> machine where you get consistent, explainable results. >>> >>> Nothing in the code is fine-tuned for a particular architecture so far, only >>> order-0 handling is kept separate. >>> >>> BTW: I see the exact same speedups for dontneed that I see for munmap. For >>> example, for order-9, it goes from 0.023412s -> 0.009785, so -58%. So I'm >>> curious why you see a speedup for munmap but not for dontneed. >> >> Ugh... ok, coming up. > > Hopefully you were just staring at the wrong numbers (e.g., only with fork > patches). Because both (munmap/pte-dontneed) are using the exact same code path. > Ahh... I'm doing pte-dontneed, which is the only option in your original benchmark - it does MADV_DONTNEED one page at a time. It looks like your new benchmark has an additional "dontneed" option that does it in one shot. Which option are you running? Assuming the latter, I think that explains it.
