On Tue 13-05-14 14:39:53, Andrew Morton wrote:
> On Tue, 13 May 2014 17:29:16 +0200 Michal Hocko <mhocko@xxxxxxx> wrote:
>
> > force_empty has been introduced primarily to drop memory before it gets
> > reparented on the group removal. This alone doesn't sound fully
> > justified because reparented pages which are not in use can be reclaimed
> > also later when there is a memory pressure on the parent level.
> >
> > Mark the knob CFTYPE_INSANE which tells the cgroup core that it
> > shouldn't create the knob with the experimental sane_behavior. Other
> > users will get informed about the deprecation and asked to tell us more
> > because I do not expect most users will use sane_behavior cgroups mode
> > very soon.
> > Anyway I expect that most users will be simply cgroup remove handlers
> > which do that since ever without having any good reason for it.
> >
> > If somebody really cares because reparented pages, which would be
> > dropped otherwise, push out more important ones then we should fix the
> > reparenting code and put pages to the tail.
> >
> > ...
> >
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -4793,6 +4793,10 @@ static int mem_cgroup_force_empty_write(struct cgroup_subsys_state *css,
> >
> > if (mem_cgroup_is_root(memcg))
> > return -EINVAL;
> > + pr_info("%s (%d): memory.force_empty is deprecated and will be removed.",
> > + current->comm, task_pid_nr(current));
> > + pr_cont(" Let us know if you know if it needed in your usecase at");
> > + pr_cont(" linux-mm@xxxxxxxxx\n");
> > return mem_cgroup_force_empty(memcg);
> > }
> >
>
> Do we really want to spam the poor user each and every time they use
> this? Using pr_info_once() is kinder and gentler?
We do not catch all potential callers but it is true that some
configurations might have thousands of cgroups and the notify_on_release
handler will spam the log.
> From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Subject: memcg-deprecate-memoryforce_empty-knob-fix
>
> - s/pr_info/pr_info_once/
> - fix garbled printk text
>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
> ---
>
> Documentation/cgroups/memory.txt | 2 +-
> mm/memcontrol.c | 8 ++++----
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff -puN Documentation/cgroups/memory.txt~memcg-deprecate-memoryforce_empty-knob-fix Documentation/cgroups/memory.txt
> --- a/Documentation/cgroups/memory.txt~memcg-deprecate-memoryforce_empty-knob-fix
> +++ a/Documentation/cgroups/memory.txt
> @@ -482,7 +482,7 @@ About use_hierarchy, see Section 6.
> memory.kmem.usage_in_bytes == memory.usage_in_bytes.
>
> Please note that this knob is considered deprecated and will be removed
> - in future.
> + in the future.
>
> About use_hierarchy, see Section 6.
>
> diff -puN mm/memcontrol.c~memcg-deprecate-memoryforce_empty-knob-fix mm/memcontrol.c
> --- a/mm/memcontrol.c~memcg-deprecate-memoryforce_empty-knob-fix
> +++ a/mm/memcontrol.c
> @@ -4799,10 +4799,10 @@ static int mem_cgroup_force_empty_write(
>
> if (mem_cgroup_is_root(memcg))
> return -EINVAL;
> - pr_info("%s (%d): memory.force_empty is deprecated and will be removed.",
> - current->comm, task_pid_nr(current));
> - pr_cont(" Let us know if you know if it needed in your usecase at");
> - pr_cont(" linux-mm@xxxxxxxxx\n");
> + pr_info_once("%s (%d): memory.force_empty is deprecated and will be "
> + "removed. Let us know if it is needed in your usecase at "
> + "linux-mm@xxxxxxxxx\n",
> + current->comm, task_pid_nr(current));
> return mem_cgroup_force_empty(memcg);
> }
>
> _
>
--
Michal Hocko
SUSE Labs
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