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    SubjectRe: [PATCH v13 5/7] mm, oom: add cgroup v2 mount option for cgroup-aware OOM killer
    On Thu 30-11-17 15:28:22, Roman Gushchin wrote:
    > Add a "groupoom" cgroup v2 mount option to enable the cgroup-aware
    > OOM killer. If not set, the OOM selection is performed in
    > a "traditional" per-process way.
    >
    > The behavior can be changed dynamically by remounting the cgroupfs.

    Is it ok to create oom_group if the option is not enabled? This looks
    confusing. I forgot all the details about how cgroup core creates file
    so I do not have a good idea how to fix this.

    > Signed-off-by: Roman Gushchin <guro@fb.com>
    > Cc: Michal Hocko <mhocko@kernel.org>
    > Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
    > Cc: Johannes Weiner <hannes@cmpxchg.org>
    > Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    > Cc: David Rientjes <rientjes@google.com>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Tejun Heo <tj@kernel.org>
    > Cc: kernel-team@fb.com
    > Cc: cgroups@vger.kernel.org
    > Cc: linux-doc@vger.kernel.org
    > Cc: linux-kernel@vger.kernel.org
    > Cc: linux-mm@kvack.org
    > ---
    > include/linux/cgroup-defs.h | 5 +++++
    > kernel/cgroup/cgroup.c | 10 ++++++++++
    > mm/memcontrol.c | 3 +++
    > 3 files changed, 18 insertions(+)
    >
    > diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
    > index 8b7fd8eeccee..9fb99e25d654 100644
    > --- a/include/linux/cgroup-defs.h
    > +++ b/include/linux/cgroup-defs.h
    > @@ -81,6 +81,11 @@ enum {
    > * Enable cpuset controller in v1 cgroup to use v2 behavior.
    > */
    > CGRP_ROOT_CPUSET_V2_MODE = (1 << 4),
    > +
    > + /*
    > + * Enable cgroup-aware OOM killer.
    > + */
    > + CGRP_GROUP_OOM = (1 << 5),
    > };
    >
    > /* cftype->flags */
    > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
    > index 0b1ffe147f24..7338e12979e1 100644
    > --- a/kernel/cgroup/cgroup.c
    > +++ b/kernel/cgroup/cgroup.c
    > @@ -1731,6 +1731,9 @@ static int parse_cgroup_root_flags(char *data, unsigned int *root_flags)
    > if (!strcmp(token, "nsdelegate")) {
    > *root_flags |= CGRP_ROOT_NS_DELEGATE;
    > continue;
    > + } else if (!strcmp(token, "groupoom")) {
    > + *root_flags |= CGRP_GROUP_OOM;
    > + continue;
    > }
    >
    > pr_err("cgroup2: unknown option \"%s\"\n", token);
    > @@ -1747,6 +1750,11 @@ static void apply_cgroup_root_flags(unsigned int root_flags)
    > cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
    > else
    > cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
    > +
    > + if (root_flags & CGRP_GROUP_OOM)
    > + cgrp_dfl_root.flags |= CGRP_GROUP_OOM;
    > + else
    > + cgrp_dfl_root.flags &= ~CGRP_GROUP_OOM;
    > }
    > }
    >
    > @@ -1754,6 +1762,8 @@ static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root
    > {
    > if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
    > seq_puts(seq, ",nsdelegate");
    > + if (cgrp_dfl_root.flags & CGRP_GROUP_OOM)
    > + seq_puts(seq, ",groupoom");
    > return 0;
    > }
    >
    > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > index 5d27a4bbd478..c76d5fb55c5c 100644
    > --- a/mm/memcontrol.c
    > +++ b/mm/memcontrol.c
    > @@ -2869,6 +2869,9 @@ bool mem_cgroup_select_oom_victim(struct oom_control *oc)
    > if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
    > return false;
    >
    > + if (!(cgrp_dfl_root.flags & CGRP_GROUP_OOM))
    > + return false;
    > +
    > if (oc->memcg)
    > root = oc->memcg;
    > else
    > --
    > 2.14.3

    --
    Michal Hocko
    SUSE Labs

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