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

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Date:   Fri, 20 Apr 2018 10:29:13 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, kernel-team@...com,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 1/2] mm: introduce memory.min

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@...radead.org> # for Documentation/ only.

> ------------------------------------------------------------
> 
> 
> From 2225fa0b3400431dd803f206b20a9344f0dfcd0a Mon Sep 17 00:00:00 2001
> From: Roman Gushchin <guro@...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@...com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
> Cc: Tejun Heo <tj@...nel.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