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

[Martin J. Bligh]

> 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.

I think it'd make more sense to only use vmalloc when it's explicitly 
too big for kmalloc - or simply switch on num_online_cpus > 100 or 
whatever a sensible cutoff is (ie nobody but you would ever see this ;-))

M.

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