linux-kernel - Re: [Patch 6/8] mqueue: don't use kmalloc with KMALLOC_MAX

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Date:	Wed, 18 Apr 2012 03:24:04 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Doug Ledford <dledford@...hat.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	kosaki.motohiro@...il.com,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KOSAKI Motohiro <mkosaki@...fujitsu.com>,
	Amerigo Wang <amwang@...hat.com>,
	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	Jiri Slaby <jslaby@...e.cz>, Dave Hansen <haveblue@...ibm.com>
Subject: Re: [Patch 6/8] mqueue: don't use kmalloc with KMALLOC_MAX_SIZE

Quoting Doug Ledford (dledford@...hat.com):
> From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> 
> KMALLOC_MAX_SIZE is no good threshold. It is extream high and
> problematic. Unfortunately, some silly drivers depend on and
> we can't change it. but any new code don't use such extream
> ugly high order allocations. It bring us awful fragmentation
> issue and system slowdown.
> 
> Signed-off-by: KOSAKI Motohiro <mkosaki@...fujitsu.com>
> Acked-by: Doug Ledford <dledford@...hat.com>
> Acked-by: Joe Korty <joe.korty@...r.com>
> Cc: Amerigo Wang <amwang@...hat.com>
> Cc: Serge E. Hallyn <serue@...ibm.com>

Looks reasonable to me, but that doesn't mean much.  Cc:d Dave Hansen
explicitly, he'd have a better idea.

> Cc: Jiri Slaby <jslaby@...e.cz>
> ---
>  ipc/mqueue.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/ipc/mqueue.c b/ipc/mqueue.c
> index 3ced596..f9f0782 100644
> --- a/ipc/mqueue.c
> +++ b/ipc/mqueue.c
> @@ -150,7 +150,7 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
>  			info->attr.mq_msgsize = attr->mq_msgsize;
>  		}
>  		mq_msg_tblsz = info->attr.mq_maxmsg * sizeof(struct msg_msg *);
> -		if (mq_msg_tblsz > KMALLOC_MAX_SIZE)
> +		if (mq_msg_tblsz > PAGE_SIZE)
>  			info->messages = vmalloc(mq_msg_tblsz);
>  		else
>  			info->messages = kmalloc(mq_msg_tblsz, GFP_KERNEL);
> @@ -263,7 +263,7 @@ static void mqueue_evict_inode(struct inode *inode)
>  	spin_lock(&info->lock);
>  	for (i = 0; i < info->attr.mq_curmsgs; i++)
>  		free_msg(info->messages[i]);
> -	if (info->attr.mq_maxmsg * sizeof(struct msg_msg *) > KMALLOC_MAX_SIZE)
> +	if (is_vmalloc_addr(info->messages))
>  		vfree(info->messages);
>  	else
>  		kfree(info->messages);
> -- 
> 1.7.7.6
> 
> --
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