linux-kernel - Re: [PATCH 1/7] cgroups: Shrink struct cgroup

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Date:	Mon, 08 Nov 2010 13:23:18 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Paul Menage <menage@...gle.com>
CC:	"akpm >> Andrew Morton" <akpm@...ux-foundation.org>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	containers@...ts.linux-foundation.org
Subject: Re: [PATCH 1/7] cgroups: Shrink struct cgroup_subsys

(Sorry for the delayed reply)

Paul Menage wrote:
> On Fri, Oct 22, 2010 at 1:09 AM, Li Zefan <lizf@...fujitsu.com> wrote:
>> On x86_32, sizeof(struct cgroup_subsys) shrinks from 276 bytes
>> to 264.
>>
>> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> 
> Acked-by: Paul Menage <menage@...gle.com>
> 
> Maybe use "bool" here?
> 

Do you mean:

bool active;
bool disabled;
...

?

With alignment 5-8 bool values == 8 bytes in 64-bit machine, compared to
4 bytes with the approach this patch takes.

> Paul
> 
>> ---
>> include/linux/cgroup.h |   10 ++++++----
>>  1 files changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
>> index ed4ba11..e23ded6 100644
>> --- a/include/linux/cgroup.h
>> +++ b/include/linux/cgroup.h
>> @@ -481,14 +481,16 @@ struct cgroup_subsys {
>>        void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
>>
>>        int subsys_id;
>> -       int active;
>> -       int disabled;
>> -       int early_init;
>> +
>> +       unsigned int active:1;
>> +       unsigned int disabled:1;
>> +       unsigned int early_init:1;
>>        /*
>>         * True if this subsys uses ID. ID is not available before cgroup_init()
>>         * (not available in early_init time.)
>>         */
>> -       bool use_id;
>> +       unsigned int use_id:1;
>> +
>>  #define MAX_CGROUP_TYPE_NAMELEN 32
>>        const char *name;
>>
>> --
>> 1.7.0.1
>>
>>
--
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