linux-kernel - Re: [Patch] ipc: HARD_MSGMAX should be higher not lower on 64bit

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Message-ID: <20091211152115.GA2414@hack>
Date:	Fri, 11 Dec 2009 23:21:15 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Amerigo Wang <amwang@...hat.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, Cedric Le Goater <clg@...ibm.com>
Subject: Re: [Patch] ipc: HARD_MSGMAX should be higher not lower on 64bit


(Hi, I am the same person.)

On Fri, Dec 11, 2009 at 08:44:33AM -0600, Serge E. Hallyn wrote:
>Quoting Amerigo Wang (amwang@...hat.com):
>> It looks weird that we have HARD_MSGMAX lower on 64bit than on 32bit,
>> since usually 64bit machines have more memory than 32bit machines.
>
>It does look like this may have been an accident.
>

OK.

>> Making it higher on 64bit seems reasonable, and keep the original
>> number on 32bit.
>> 
>> Cc: Serge E. Hallyn <serue@...ibm.com>
>> Cc: Cedric Le Goater <clg@...ibm.com>
>> Signed-off-by: WANG Cong <amwang@...hat.com>
>> 
>> ---
>> diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
>> index e408722..07baa38 100644
>> --- a/include/linux/ipc_namespace.h
>> +++ b/include/linux/ipc_namespace.h
>> @@ -87,7 +87,7 @@ extern int mq_init_ns(struct ipc_namespace *ns);
>>  /* default values */
>>  #define DFLT_QUEUESMAX 256     /* max number of message queues */
>>  #define DFLT_MSGMAX    10      /* max number of messages in each queue */
>> -#define HARD_MSGMAX    (131072/sizeof(void *))
>> +#define HARD_MSGMAX    (32768*sizeof(void *)/4)
>
>why /4 ?  You're now making it much smaller for 32-bit than it
>used to be?
>

Yes?

Before this patch, it is 131072/sizeof(void*) = 32768;
after this patch, it is 32768*sizeof(void*)/4 = 32768 too.
Both on 32bit, of course.

Am I missing something?


-- 
Live like a child, think like the god.
 
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