Re: [PATCH] Allocate module.ref array dynamically

From: Eric Dumazet
Date: Tue Nov 11 2008 - 17:07:23 EST


Takashi Iwai a écrit :
Hi,

we found that the kernel module sizes and memory footprints
grow drastically when NR_CPUS is high. For example, with
NR_CPUS=4096, SUSE kernel packages weigh over 500MB (even w/o debug
info).

A part of the reason is the fixed size array in struct module.
The patch below fixes the problem by allocating it dynamically.
With the patch, the size can go down to 20MB.


Any comments/suggestions appreciated.


Many attempts were done on this area on the past.

Your patch has the drawback of using kcalloc(), while previously, module_ref
space was allocated with vmalloc().

After a while, a machine could have a lot of vmalloc() space available, but not enough
physically contiguous space to fullfill a kmalloc(large_area) call.

So a module load could fail, while previous code could load module.

I believe Mike Travis has a better patch for this problem, partly using new percpu allocator.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/