On Mon 28-03-11 18:11:27, KAMEZAWA Hiroyuki wrote:

On Mon, 28 Mar 2011 09:43:42 +0200
Michal Hocko [off-list ref] wrote:

quoted

On Mon 28-03-11 13:25:50, Daisuke Nishimura wrote:

quoted

From: Daisuke Nishimura <redacted>

[...]

quoted

quoted

+5.5 usage_in_bytes
+
+As described in 2.1, memory cgroup uses res_counter for tracking and limiting
+the memory usage. memory.usage_in_bytes shows the current res_counter usage for
+memory, and DOESN'T show a actual usage of RSS and Cache. It is usually bigger
+than the actual usage for a performance improvement reason. 

Isn't an explicit mention about caching charges better?

It's difficult to distinguish which is spec. and which is implemnation details...

Sure. At least commit log should contain the implementation details IMO,
though.

My one here ;)
==
5.5 usage_in_bytes

For efficiency, as other kernel components, memory cgroup uses some optimization to
avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the
method and doesn't show 'exact' value of usage, it's an fuzz value for efficient
access. (Of course, when necessary, it's synchronized.)
In usual, the value (RSS+CACHE) in memory.stat shows more exact value. IOW,

- In usual, the value (RSS+CACHE) in memory.stat shows more exact value. IOW,
+ (RSS+CACHE) value from memory.stat shows more exact value and should be used
+ by userspace. IOW,

?

usage_in_bytes is less exact than memory.stat. The error will be larger on the larger
hardwares which have many cpus and tasks.
==

Hmm ?

Looks much better.

Thanks
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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