Re: [PATCH 1/2] mm: introduce memory.min

Randy Dunlap
2018-04-20T17:29:13Z

On 04/20/18 10:20, Roman Gushchin wrote:
>
> Hi, Randy!
>
> An updated version below.
>
> Thanks!

OK, looks good now. Thanks.

FWIW:
Reviewed-by: Randy Dunlap <rdunlap@infradead.org> # for Documentation/ only.

> ------------------------------------------------------------
>
>
> From 2225fa0b3400431dd803f206b20a9344f0dfcd0a Mon Sep 17 00:00:00 2001
> From: Roman Gushchin <guro@fb.com>
> Date: Fri, 20 Apr 2018 15:24:44 +0100
> Subject: [PATCH 1/2] mm: introduce memory.min
>
> Memory controller implements the memory.low best-effort memory
> protection mechanism, which works perfectly in many cases and
> allows protecting working sets of important workloads from
> sudden reclaim.
>
> But it's semantics has a significant limitation: it works
> only until there is a supply of reclaimable memory.
> This makes it pretty useless against any sort of slow memory
> leaks or memory usage increases. This is especially true
> for swapless systems. If swap is enabled, memory soft protection
> effectively postpones problems, allowing a leaking application
> to fill all swap area, which makes no sense.
> The only effective way to guarantee the memory protection
> in this case is to invoke the OOM killer.
>
> This patch introduces the memory.min interface for cgroup v2
> memory controller. It works very similarly to memory.low
> (sharing the same hierarchical behavior), except that it's
> not disabled if there is no more reclaimable memory in the system.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Tejun Heo <tj@kernel.org>
> ---
> Documentation/cgroup-v2.txt | 24 ++++++++++-
> include/linux/memcontrol.h | 15 ++++++-
> include/linux/page_counter.h | 11 ++++-
> mm/memcontrol.c | 99 ++++++++++++++++++++++++++++++++++++--------
> mm/page_counter.c | 63 ++++++++++++++++++++--------
> mm/vmscan.c | 19 ++++++++-
> 6 files changed, 191 insertions(+), 40 deletions(-)
>
> diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
> index 657fe1769c75..a413118b9c29 100644
> --- a/Documentation/cgroup-v2.txt
> +++ b/Documentation/cgroup-v2.txt
> @@ -1002,6 +1002,26 @@ PAGE_SIZE multiple when read back.
> The total amount of memory currently being used by the cgroup
> and its descendants.
>
> + memory.min
> + A read-write single value file which exists on non-root
> + cgroups. The default is "0".
> +
> + Hard memory protection. If the memory usage of a cgroup
> + is within its effective min boundary, the cgroup's memory
> + won't be reclaimed under any conditions. If there is no
> + unprotected reclaimable memory available, OOM killer
> + is invoked.
> +
> + Effective low boundary is limited by memory.min values of
> + all ancestor cgroups. If there is memory.min overcommitment
> + (child cgroup or cgroups are requiring more protected memory
> + than parent will allow), then each child cgroup will get
> + the part of parent's protection proportional to its
> + actual memory usage below memory.min.
> +
> + Putting more memory than generally available under this
> + protection is discouraged and may lead to constant OOMs.
> +
> memory.low
> A read-write single value file which exists on non-root
> cgroups. The default is "0".
> @@ -1013,9 +1033,9 @@ PAGE_SIZE multiple when read back.
>
> Effective low boundary is limited by memory.low values of
> all ancestor cgroups. If there is memory.low overcommitment
> - (child cgroup or cgroups are requiring more protected memory,
> + (child cgroup or cgroups are requiring more protected memory
> than parent will allow), then each child cgroup will get
> - the part of parent's protection proportional to the its
> + the part of parent's protection proportional to its
> actual memory usage below memory.low.
>
> Putting more memory than generally available under this

--
~Randy