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

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Date:	Fri, 11 Dec 2009 08:44:33 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	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

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.

> 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?

>  #define DFLT_MSGSIZEMAX 8192   /* max message size */
>  #else
>  static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
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