Re: [PATCH] [RFC] slub tracing: move trace calls out of always inlined functions to reduce kernel code size

Pekka Enberg
2010-10-14T07:09:47Z

On 10/13/10 7:09 PM, Richard Kennedy wrote:
> Having the trace calls defined in the always inlined kmalloc functions
> in include/linux/slub_def.h causes a lot of code duplication as the
> trace functions get instantiated for each kamalloc call site. This can
> simply be removed by pushing the trace calls down into the functions in
> slub.c.
>
> On my x86_64 built this patch shrinks the code size of the kernel by
> approx 29K and also shrinks the code size of many modules -- too many to
> list here ;)
>
> size vmlinux.o reports
> text data bss dec hex filename
> 4777011 602052 763072 6142135 5db8b7 vmlinux.o
> 4747120 602388 763072 6112580 5d4544 vmlinux.o.patch

Impressive kernel text savings!

> index 13fffe1..32b89ee 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> +void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
> +{
> + void *ret = (void *) __get_free_pages(flags | __GFP_COMP, order);
> +
> + kmemleak_alloc(ret, size, 1, flags);
> + trace_kmalloc(_RET_IP_, ret, size, PAGE_SIZE<< order, flags);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(kmalloc_order);
> +
This doesn't make sense to be out-of-line for the !CONFIG_TRACE case.
I'd just wrap that with "#ifdef CONFIG_TRACE" and put an inline version
in the header for !TRACE.

Pekka