Re: [External] Re: [PATCH v3] mm: memcontrol: Add the missing numa_stat interface for cgroup v2

[Muchun Song <songmuchun@bytedance.com>]

On Tue, Sep 15, 2020 at 3:07 AM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> On 9/13/20 12:00 AM, Muchun Song wrote:
> > In the cgroup v1, we have a numa_stat interface. This is useful for
> > providing visibility into the numa locality information within an
> > memcg since the pages are allowed to be allocated from any physical
> > node. One of the use cases is evaluating application performance by
> > combining this information with the application's CPU allocation.
> > But the cgroup v2 does not. So this patch adds the missing information.
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > Suggested-by: Shakeel Butt <shakeelb@google.com>
> > Reported-by: kernel test robot <lkp@intel.com>
> > ---
> >  changelog in v3:
> >  1. Fix compiler error on powerpc architecture reported by kernel test robot.
> >  2. Fix a typo from "anno" to "anon".
> >
> >  changelog in v2:
> >  1. Add memory.numa_stat interface in cgroup v2.
> >
> >  Documentation/admin-guide/cgroup-v2.rst |  72 ++++++++++++++++
> >  mm/memcontrol.c                         | 107 ++++++++++++++++++++++++
> >  2 files changed, 179 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> > index 6be43781ec7f..92207f0012e4 100644
> > --- a/Documentation/admin-guide/cgroup-v2.rst
> > +++ b/Documentation/admin-guide/cgroup-v2.rst
> > @@ -1368,6 +1368,78 @@ PAGE_SIZE multiple when read back.
> >               collapsing an existing range of pages. This counter is not
> >               present when CONFIG_TRANSPARENT_HUGEPAGE is not set.
> >
> > +  memory.numa_stat
> > +     A read-only flat-keyed file which exists on non-root cgroups.
> > +
> > +     This breaks down the cgroup's memory footprint into different
> > +     types of memory, type-specific details, and other information
> > +     per node on the state of the memory management system.
> > +
> > +     This is useful for providing visibility into the numa locality
>
> capitalize acronyms, please:                             NUMA

OK, I will do that. Thanks.

>
>
> > +     information within an memcg since the pages are allowed to be
> > +     allocated from any physical node. One of the use cases is evaluating
> > +     application performance by combining this information with the
> > +     application's CPU allocation.
> > +
> > +     All memory amounts are in bytes.
> > +
> > +     The output format of memory.numa_stat is::
> > +
> > +       type N0=<node 0 pages> N1=<node 1 pages> ...
>
> Now I'm confused.  5 lines above here it says "All memory amounts are in bytes"
> but these appear to be in pages. Which is it?  and what size pages if that matters?

Sorry. It's my mistake. I will fix it.

>
> Is it like this?
>           type N0=<bytes in node 0 pages> N1=<bytes in node 1 pages> ...

Thanks.

>
>
>
> > +     The entries are ordered to be human readable, and new entries
> > +     can show up in the middle. Don't rely on items remaining in a
> > +     fixed position; use the keys to look up specific values!
> > +
> > +       anon
> > +             Amount of memory per node used in anonymous mappings such
> > +             as brk(), sbrk(), and mmap(MAP_ANONYMOUS)
> > +
> > +       file
> > +             Amount of memory per node used to cache filesystem data,
> > +             including tmpfs and shared memory.
> > +
> > +       kernel_stack
> > +             Amount of memory per node allocated to kernel stacks.
> > +
> > +       shmem
> > +             Amount of cached filesystem data per node that is swap-backed,
> > +             such as tmpfs, shm segments, shared anonymous mmap()s
> > +
> > +       file_mapped
> > +             Amount of cached filesystem data per node mapped with mmap()
> > +
> > +       file_dirty
> > +             Amount of cached filesystem data per node that was modified but
> > +             not yet written back to disk
> > +
> > +       file_writeback
> > +             Amount of cached filesystem data per node that was modified and
> > +             is currently being written back to disk
> > +
> > +       anon_thp
> > +             Amount of memory per node used in anonymous mappings backed by
> > +             transparent hugepages
> > +
> > +       inactive_anon, active_anon, inactive_file, active_file, unevictable
> > +             Amount of memory, swap-backed and filesystem-backed,
> > +             per node on the internal memory management lists used
> > +             by the page reclaim algorithm.
> > +
> > +             As these represent internal list state (eg. shmem pages are on anon
>
>                                                          e.g.

Thanks.

>
> > +             memory management lists), inactive_foo + active_foo may not be equal to
> > +             the value for the foo counter, since the foo counter is type-based, not
> > +             list-based.
> > +
> > +       slab_reclaimable
> > +             Amount of memory per node used for storing in-kernel data
> > +             structures which might be reclaimed, such as dentries and
> > +             inodes.
> > +
> > +       slab_unreclaimable
> > +             Amount of memory per node used for storing in-kernel data
> > +             structures which cannot be reclaimed on memory pressure.
>
> Some of the descriptions above end with a '.' and some do not. Please be consistent.

Will do that.

>
> > +
> >    memory.swap.current
> >       A read-only single value file which exists on non-root
> >       cgroups.
>
>
> thanks.
> --
> ~Randy
>


-- 
Yours,
Muchun