linux-kernel - Re: [PATCH 3/6] cgroup: clean up cgroup

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Date:	Mon, 20 Jan 2014 14:13:37 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	lizefan@...wei.com, containers@...ts.linux-foundation.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Balbir Singh <bsingharora@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Aristeu Rozanski <aris@...hat.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Vivek Goyal <vgoyal@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Thomas Graf <tgraf@...g.ch>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3/6] cgroup: clean up cgroup_subsys names and
 initialization

On Fri 17-01-14 13:11:54, Tejun Heo wrote:
> cgroup_subsys is a bit messier than it needs to be.
> 
> * The name of a subsys can be different from its internal identifier
>   defined in cgroup_subsys.h.  Most subsystems use the matching name
>   but three - cpu, memory and perf_event - use different ones.
> 
> * cgroup_subsys_id enums are postfixed with _subsys_id and each
>   cgroup_subsys is postfixed with _subsys.  cgroup.h is widely
>   included throughout various subsystems, it doesn't and shouldn't
>   have claim on such generic names which don't have any qualifier
>   indicating that they belong to cgroup.
> 
> * cgroup_subsys->subsys_id should always equal the matching
>   cgroup_subsys_id enum; however, we require each controller to
>   initialize it and then BUG if they don't match, which is a bit
>   silly.
> 
> This patch cleans up cgroup_subsys names and initialization by doing
> the followings.
> 
> * cgroup_subsys_id enums are now postfixed with _cgrp_id, and each
>   cgroup_subsys with _cgrp_subsys.
> 
> * With the above, renaming subsys identifiers to match the userland
>   visible names doesn't cause any naming conflicts.  All non-matching
>   identifiers are renamed to match the official names.
> 
>   cpu_cgroup -> cpu
>   mem_cgroup -> memory
>   perf -> perf_event
> 
> * controllers no longer need to initialize ->subsys_id and ->name.
>   They're generated in cgroup core and set automatically during boot.
> 
> * Redundant cgroup_subsys declarations removed.
> 
> * While updating BUG_ON()s in cgroup_init_early(), convert them to
>   WARN()s.  BUGging that early during boot is stupid - the kernel
>   can't print anything, even through serial console and the trap
>   handler doesn't even link stack frame properly for back-tracing.
> 
> This patch doesn't introduce any behavior changes.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Li Zefan <lizefan@...wei.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...e.cz>
> Cc: Balbir Singh <bsingharora@...il.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Aristeu Rozanski <aris@...hat.com>
> Cc: Serge E. Hallyn <serue@...ibm.com>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: Neil Horman <nhorman@...driver.com>
> Cc: Thomas Graf <tgraf@...g.ch>
> Cc: "David S. Miller" <davem@...emloft.net>

For memcg and hugetlb
Acked-by: Michal Hocko <mhocko@...e.cz>

[...]

Thanks!
-- 
Michal Hocko
SUSE Labs
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