Re: [PATCH] memcg: fix a typo in documentation

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, Dec 09, 2011 at 04:15:20PM -0800, Ying Han wrote:
> A tiny typo on mapped_file stat.
> 
> Signed-off-by: Ying Han <yinghan@google.com>
> ---
>  Documentation/cgroups/memory.txt |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> index 070c016..c0f409e 100644
> --- a/Documentation/cgroups/memory.txt
> +++ b/Documentation/cgroups/memory.txt
> @@ -410,7 +410,7 @@ hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
>  
>  total_cache		- sum of all children's "cache"
>  total_rss		- sum of all children's "rss"
> -total_mapped_file	- sum of all children's "cache"
> +total_mapped_file	- sum of all children's "mapped_file"
>  total_mlock		- sum of all children's "mlock"
>  total_pgpgin		- sum of all children's "pgpgin"
>  total_pgpgout		- sum of all children's "pgpgout"

Your fix obviously makes sense, but the line is still incorrect: it's
not just the sum of all children but that of the full hierarchy
starting with the consulted memcg.  It includes that memcg's local
counter as well.  Aside from that, this all seems awefully redundant.

How about this on top?

---
From: Johannes Weiner <hannes@cmpxchg.org>
Subject: [patch] Documentation: memcg: future proof hierarchical statistics
 documentation

The hierarchical versions of per-memcg counters in memory.stat are all
calculated the same way and are all named total_<counter>.

Documenting the pattern is easier for maintenance than listing each
counter twice.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 Documentation/cgroups/memory.txt |   15 ++++-----------
 1 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 06eb6d9..a858675 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -404,17 +404,10 @@ hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
 hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
 			hierarchy under which memory cgroup is.
 
-total_cache		- sum of all children's "cache"
-total_rss		- sum of all children's "rss"
-total_mapped_file	- sum of all children's "mapped_file"
-total_pgpgin		- sum of all children's "pgpgin"
-total_pgpgout		- sum of all children's "pgpgout"
-total_swap		- sum of all children's "swap"
-total_inactive_anon	- sum of all children's "inactive_anon"
-total_active_anon	- sum of all children's "active_anon"
-total_inactive_file	- sum of all children's "inactive_file"
-total_active_file	- sum of all children's "active_file"
-total_unevictable	- sum of all children's "unevictable"
+total_<counter>		- # hierarchical version of <counter>, which in
+			addition to the cgroup's own value includes the
+			sum of all hierarchical children's values of
+			<counter>, i.e. total_cache
 
 # The following additional stats are dependent on CONFIG_DEBUG_VM.
 
-- 
1.7.7.3

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