Re: [PATCH] mm, memcg: cg2 memory{.swap,}.peak write handlers

[Michal Hocko <mhocko@suse.com>]

On Mon 15-07-24 16:36:26, David Finkel wrote:
> Other mechanisms for querying the peak memory usage of either a process
> or v1 memory cgroup allow for resetting the high watermark. Restore
> parity with those mechanisms.
> 
> For example:
>  - Any write to memory.max_usage_in_bytes in a cgroup v1 mount resets
>    the high watermark.
>  - writing "5" to the clear_refs pseudo-file in a processes's proc
>    directory resets the peak RSS.
> 
> This change copies the cgroup v1 behavior so any write to the
> memory.peak and memory.swap.peak pseudo-files reset the high watermark
> to the current usage.
> 
> This behavior is particularly useful for work scheduling systems that
> need to track memory usage of worker processes/cgroups per-work-item.
> Since memory can't be squeezed like CPU can (the OOM-killer has
> opinions), these systems need to track the peak memory usage to compute
> system/container fullness when binpacking workitems.
> 
> Signed-off-by: David Finkel <davidf@vimeo.com>

As mentioned down the email thread, I consider usefulness of peak value
rather limited. It is misleading when memory is reclaimed. But
fundamentally I do not oppose to unifying the write behavior to reset
values.

The chnagelog could use some of the clarifications down the thread.

Acked-by: Michal Hocko <mhocko@suse.com>

-- 
Michal Hocko
SUSE Labs