On 10/01/2024 09:09, Barry Song wrote: > On Wed, Jan 10, 2024 at 4:58 PM Ryan Roberts <ryan.roberts@xxxxxxx> wrote: >> >> On 10/01/2024 08:02, Barry Song wrote: >>> On Wed, Jan 10, 2024 at 12:16 PM John Hubbard <jhubbard@xxxxxxxxxx> wrote: >>>> >>>> On 1/9/24 19:51, Barry Song wrote: >>>>> On Wed, Jan 10, 2024 at 11:35 AM John Hubbard <jhubbard@xxxxxxxxxx> wrote: >>>> ... >>>>>> Hi Ryan, >>>>>> >>>>>> One thing that immediately came up during some recent testing of mTHP >>>>>> on arm64: the pid requirement is sometimes a little awkward. I'm running >>>>>> tests on a machine at a time for now, inside various containers and >>>>>> such, and it would be nice if there were an easy way to get some numbers >>>>>> for the mTHPs across the whole machine. >> >> Just to confirm, you're expecting these "global" stats be truely global and not >> per-container? (asking because you exploicitly mentioned being in a container). >> If you want per-container, then you can probably just create the container in a >> cgroup? >> >>>>>> >>>>>> I'm not sure if that changes anything about thpmaps here. Probably >>>>>> this is fine as-is. But I wanted to give some initial reactions from >>>>>> just some quick runs: the global state would be convenient. >> >> Thanks for taking this for a spin! Appreciate the feedback. >> >>>>> >>>>> +1. but this seems to be impossible by scanning pagemap? >>>>> so may we add this statistics information in kernel just like >>>>> /proc/meminfo or a separate /proc/mthp_info? >>>>> >>>> >>>> Yes. From my perspective, it looks like the global stats are more useful >>>> initially, and the more detailed per-pid or per-cgroup stats are the >>>> next level of investigation. So feels odd to start with the more >>>> detailed stats. >>>> >>> >>> probably because this can be done without the modification of the kernel. >> >> Yes indeed, as John said in an earlier thread, my previous attempts to add stats >> directly in the kernel got pushback; DavidH was concerned that we don't really >> know exectly how to account mTHPs yet >> (whole/partial/aligned/unaligned/per-size/etc) so didn't want to end up adding >> the wrong ABI and having to maintain it forever. There has also been some >> pushback regarding adding more values to multi-value files in sysfs, so David >> was suggesting coming up with a whole new scheme at some point (I know >> /proc/meminfo isn't sysfs, but the equivalent files for NUMA nodes and cgroups >> do live in sysfs). >> >> Anyway, this script was my attempt to 1) provide a short term solution to the >> "we need some stats" request and 2) provide a context in which to explore what >> the right stats are - this script can evolve without the ABI problem. >> >>> The detailed per-pid or per-cgroup is still quite useful to my case in which >>> we set mTHP enabled/disabled and allowed sizes according to vma types, >>> eg. libc_malloc, java heaps etc. >>> >>> Different vma types can have different anon_name. So I can use the detailed >>> info to find out if specific VMAs have gotten mTHP properly and how many >>> they have gotten. >>> >>>> However, Ryan did clearly say, above, "In future we may wish to >>>> introduce stats directly into the kernel (e.g. smaps or similar)". And >>>> earlier he ran into some pushback on trying to set up /proc or /sys >>>> values because this is still such an early feature. >>>> >>>> I wonder if we could put the global stats in debugfs for now? That's >>>> specifically supposed to be a "we promise *not* to keep this ABI stable" >>>> location. >> >> Now that I think about it, I wonder if we can add a --global mode to the script >> (or just infer global when neither --pid nor --cgroup are provided). I think I >> should be able to determine all the physical memory ranges from /proc/iomem, >> then grab all the info we need from /proc/kpageflags. We should then be able to >> process it all in much the same way as for --pid/--cgroup and provide the same >> stats, but it will apply globally. What do you think? > > for debug purposes, it should be good. imaging there is a health > monitor which needs > to sample the stats of large folios online and periodically, this > might be too expensive. Yes, understood - the long term aim needs to be to get stats into the kernel. This is intended as a step to help make that happen. > >> >> If we can possibly avoid sysfs/debugfs I would prefer to keep it all in a script >> for now. >> >>> >>> +1. >>> >>>> >>>> >>>> thanks, >>>> -- >>>> John Hubbard >>>> NVIDIA >>>> >>> > > Thanks > Barry
