From: Andrew Morton <akpm@linux-foundation.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [patch 6/6] mm: memcg: print statistics from live counters
Date: Wed, 16 May 2012 16:01:31 -0700 [thread overview]
Message-ID: <20120516160131.fecb5ddf.akpm@linux-foundation.org> (raw)
In-Reply-To: <1337018451-27359-7-git-send-email-hannes@cmpxchg.org>
On Mon, 14 May 2012 20:00:51 +0200
Johannes Weiner <hannes@cmpxchg.org> wrote:
> Directly print statistics and event counters instead of going through
> an intermediate accumulation stage into a separate array, which used
> to require defining statistic items in more than one place.
>
> ...
>
> -static const char *memcg_stat_strings[NR_MCS_STAT] = {
> - "cache",
> - "rss",
> - "mapped_file",
Bah humbug, who went and called this mapped_file?
This stat is derived from MEM_CGROUP_STAT_FILE_MAPPED. But if we
rename MEM_CGROUP_STAT_FILE_MAPPED to MEM_CGROUP_STAT_MAPPED_FILE then
we also need to rename the non-memcg NR_FILE_MAPPED. And we can't
change the text to "file_mapped" because it's ABI.
> - "mlock",
> - "swap",
And "swap" is derived from MEM_CGROUP_STAT_SWAPOUT. We could rename
that to MEM_CGROUP_STAT_SWAP without trouble.
But both are poor names. There are two concepts here: a) swapout
events (ie: swap writeout initiation) and b) swapspace usage. Type a)
only ever counts up, whereas type b) counts up and down.
MEM_CGROUP_STAT_SWAPOUT is actually of type b), but "swapout" is a
misleading term, because it refers to type a) events.
And the human-displayed "swap" is useless because it can refer to
either type a) or type b) events. These should be called "swapped" and
MEM_CGROUP_STAT_SWAPPED. But we can't change the userspace interface.
argh, I hate you all!
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next prev parent reply other threads:[~2012-05-16 23:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-14 18:00 [patch 0/6] mm: memcg: statistics implementation cleanups Johannes Weiner
2012-05-14 18:00 ` [patch 1/6] mm: memcg: remove obsolete statistics array boundary enum item Johannes Weiner
2012-05-15 14:14 ` Michal Hocko
2012-05-14 18:00 ` [patch 2/6] mm: memcg: convert numa stat to read_seq_string interface Johannes Weiner
2012-05-15 14:43 ` Michal Hocko
2012-05-14 18:00 ` [patch 3/6] mm: memcg: print statistics directly to seq_file Johannes Weiner
2012-05-15 14:46 ` Michal Hocko
2012-05-14 18:00 ` [patch 4/6] mm: memcg: keep ratelimit counter separate from event counters Johannes Weiner
2012-05-15 14:58 ` Michal Hocko
2012-05-14 18:00 ` [patch 5/6] mm: memcg: group swapped-out statistics counter logically Johannes Weiner
2012-05-15 15:04 ` Michal Hocko
2012-05-14 18:00 ` [patch 6/6] mm: memcg: print statistics from live counters Johannes Weiner
2012-05-15 15:27 ` Michal Hocko
2012-05-16 23:01 ` Andrew Morton [this message]
2012-05-17 0:01 ` KAMEZAWA Hiroyuki
2012-05-17 10:56 ` Glauber Costa
2012-05-15 0:19 ` [patch 0/6] mm: memcg: statistics implementation cleanups KAMEZAWA Hiroyuki
2012-05-15 11:03 ` Johannes Weiner
2012-05-16 0:01 ` KAMEZAWA Hiroyuki
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