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. > > 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
