Re: 2.6 /proc/interrupts fails on systems with many CPUs

From: "Randy.Dunlap" <rddunlap@osdl.org>
To: Erik Jacobson <erikj@subway.americas.sgi.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.6 /proc/interrupts fails on systems with many CPUs
Date: Tue, 11 Nov 2003 09:29:31 -0800	[thread overview]
Message-ID: <20031111092931.7b6d1d91.rddunlap@osdl.org> (raw)
In-Reply-To: <Pine.SGI.4.53.0311111116440.360387@subway.americas.sgi.com>

On Tue, 11 Nov 2003 11:21:01 -0600 Erik Jacobson <erikj@subway.americas.sgi.com> wrote:

| Howdy.
| 
| On systems with lots of processors (512 for example), catting /proc/interrupts
| fails with a "not enough memory" error.
| 
| This was observed in 2.6.0-test8
| 
| I tracked this down to this in proc_misc.c:
| 
| static int interrupts_open(struct inode *inode, struct file *file)
| {
|    unsigned size = 4096 * (1 + num_online_cpus() / 8);
|    char *buf = kmalloc(size, GFP_KERNEL);
| 
| The kmalloc fails here.
| 
| I'm looking for suggestions on how to fix this.  I came up with one fix
| that seems to work OK for ia64.  I have attached it to this message.
| I'm looking for advice on what should be proposed for the real fix.

An alternative is to limit 'size' to a maximum of 128 KB (or whatever
the max. kmalloc() on ia64 is) and continue to use kmalloc().
Does that work for you?

Another alternative is to convert show_interrupts to use a seq_file
iterator.

--
~Randy
MOTD:  Always include version info.