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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Wed, 10 Nov 2021 14:27:43 +0800
Message-ID: <CAMZfGtUs6JHg7j2jQHkdywDVFXRzQTTH-ObVfDTLN90yfbKnpA@mail.gmail.com>
Subject: Re: [PATCH v4] hugetlb: Add hugetlb.*.numa_stat file
To:     Mina Almasry <almasrymina@google.com>
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shuah Khan <shuah@kernel.org>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Oscar Salvador <osalvador@suse.de>,
        Michal Hocko <mhocko@suse.com>,
        David Rientjes <rientjes@google.com>,
        Shakeel Butt <shakeelb@google.com>, Jue Wang <juew@google.com>,
        Yang Yao <ygyao@google.com>, Joanna Li <joannali@google.com>,
        Cannon Matthews <cannonmatthews@google.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Nov 9, 2021 at 5:04 AM Mina Almasry <almasrymina@google.com> wrote:
>
> For hugetlb backed jobs/VMs it's critical to understand the numa
> information for the memory backing these jobs to deliver optimal
> performance.
>
> Currently this technically can be queried from /proc/self/numa_maps, but
> there are significant issues with that. Namely:
> 1. Memory can be mapped on unmapped.
> 2. numa_maps are per process and need to be aggregated across all
>    processes in the cgroup. For shared memory this is more involved as
>    the userspace needs to make sure it doesn't double count shared
>    mappings.
> 3. I believe querying numa_maps needs to hold the mmap_lock which adds
>    to the contention on this lock.
>
> For these reasons I propose simply adding hugetlb.*.numa_stat file,
> which shows the numa information of the cgroup similarly to
> memory.numa_stat.
>
> On cgroup-v2:
>    cat /sys/fs/cgroup/unified/test/hugetlb.2MB.numa_stat
>    total=3D2097152 N0=3D2097152 N1=3D0
>
> On cgroup-v1:
>    cat /sys/fs/cgroup/hugetlb/test/hugetlb.2MB.numa_stat
>    total=3D2097152 N0=3D2097152 N1=3D0
>    hierarichal_total=3D2097152 N0=3D2097152 N1=3D0
>
> This patch was tested manually by allocating hugetlb memory and querying
> the hugetlb.*.numa_stat file of the cgroup and its parents.
> =EF=BF=BC
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Miaohe Lin <linmiaohe@huawei.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Muchun Song <songmuchun@bytedance.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Shakeel Butt <shakeelb@google.com>
> Cc: Jue Wang <juew@google.com>
> Cc: Yang Yao <ygyao@google.com>
> Cc: Joanna Li <joannali@google.com>
> Cc: Cannon Matthews <cannonmatthews@google.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
>
> Signed-off-by: Mina Almasry <almasrymina@google.com>
>
> ---
>
> Changes in v4:
> - Removed unnecessary braces.
> - usage is now counted in pages instead of bytes.
> - Reverted unneeded changes to write_to_hugetlbfs.c
>
> Changes in v3:
> - Fixed typos (sorry!)
> - Used conventional locations for cgroups mount points in docs/commit
> message.
> - Updated docs.
> - Handle kzalloc_node failure, and proper deallocation of per node data.
> - Use struct_size() to calculate the struct size.
> - Use nr_node_ids instead of MAX_NUMNODES.
> - Updated comments per multi-line comment pattern.
>
> Changes in v2:
> - Fix warning Reported-by: kernel test robot <lkp@intel.com>
> ---
>  .../admin-guide/cgroup-v1/hugetlb.rst         |   4 +
>  Documentation/admin-guide/cgroup-v2.rst       |   5 +
>  include/linux/hugetlb.h                       |   4 +-
>  include/linux/hugetlb_cgroup.h                |   7 ++
>  mm/hugetlb_cgroup.c                           | 113 ++++++++++++++++--
>  5 files changed, 122 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentat=
ion/admin-guide/cgroup-v1/hugetlb.rst
> index 338f2c7d7a1c..0fa724d82abb 100644
> --- a/Documentation/admin-guide/cgroup-v1/hugetlb.rst
> +++ b/Documentation/admin-guide/cgroup-v1/hugetlb.rst
> @@ -29,12 +29,14 @@ Brief summary of control files::
>   hugetlb.<hugepagesize>.max_usage_in_bytes             # show max "hugep=
agesize" hugetlb  usage recorded
>   hugetlb.<hugepagesize>.usage_in_bytes                 # show current us=
age for "hugepagesize" hugetlb
>   hugetlb.<hugepagesize>.failcnt                        # show the number=
 of allocation failure due to HugeTLB usage limit
> + hugetlb.<hugepagesize>.numa_stat                      # show the numa i=
nformation of the hugetlb memory charged to this cgroup
>
>  For a system supporting three hugepage sizes (64k, 32M and 1G), the cont=
rol
>  files include::
>
>    hugetlb.1GB.limit_in_bytes
>    hugetlb.1GB.max_usage_in_bytes
> +  hugetlb.1GB.numa_stat
>    hugetlb.1GB.usage_in_bytes
>    hugetlb.1GB.failcnt
>    hugetlb.1GB.rsvd.limit_in_bytes
> @@ -43,6 +45,7 @@ files include::
>    hugetlb.1GB.rsvd.failcnt
>    hugetlb.64KB.limit_in_bytes
>    hugetlb.64KB.max_usage_in_bytes
> +  hugetlb.64KB.numa_stat
>    hugetlb.64KB.usage_in_bytes
>    hugetlb.64KB.failcnt
>    hugetlb.64KB.rsvd.limit_in_bytes
> @@ -51,6 +54,7 @@ files include::
>    hugetlb.64KB.rsvd.failcnt
>    hugetlb.32MB.limit_in_bytes
>    hugetlb.32MB.max_usage_in_bytes
> +  hugetlb.32MB.numa_stat
>    hugetlb.32MB.usage_in_bytes
>    hugetlb.32MB.failcnt
>    hugetlb.32MB.rsvd.limit_in_bytes
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admi=
n-guide/cgroup-v2.rst
> index 4d8c27eca96b..356847f8f008 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -2252,6 +2252,11 @@ HugeTLB Interface Files
>         are local to the cgroup i.e. not hierarchical. The file modified =
event
>         generated on this file reflects only the local events.
>
> +  hugetlb.<hugepagesize>.numa_stat
> +       Similar to memory.numa_stat, it shows the numa information of the
> +        hugetlb pages of <hugepagesize> in this cgroup.  Only active in
> +        use hugetlb pages are included.  The per-node values are in byte=
s.
> +
>  Misc
>  ----
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 1faebe1cd0ed..0445faaa636e 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -613,8 +613,8 @@ struct hstate {
>  #endif
>  #ifdef CONFIG_CGROUP_HUGETLB
>         /* cgroup control files */
> -       struct cftype cgroup_files_dfl[7];
> -       struct cftype cgroup_files_legacy[9];
> +       struct cftype cgroup_files_dfl[8];
> +       struct cftype cgroup_files_legacy[10];
>  #endif
>         char name[HSTATE_NAME_LEN];
>  };
> diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgrou=
p.h
> index c137396129db..54ff6ec68ed3 100644
> --- a/include/linux/hugetlb_cgroup.h
> +++ b/include/linux/hugetlb_cgroup.h
> @@ -36,6 +36,11 @@ enum hugetlb_memory_event {
>         HUGETLB_NR_MEMORY_EVENTS,
>  };
>
> +struct hugetlb_cgroup_per_node {
> +       /* hugetlb usage in bytes over all hstates. */

The accounting unit is pages not bytes here.

Thanks.