On Fri, 2007-08-17 at 11:22 -0700, Andrew Morton wrote:
> On Wed, 15 Aug 2007 05:12:41 +0530 (IST)
> Satyam Sharma <[email protected]> wrote:
>
> > [PATCH] {slub, slob}: use unlikely() for kfree(ZERO_OR_NULL_PTR) check
> >
> > Considering kfree(NULL) would normally occur only in error paths and
> > kfree(ZERO_SIZE_PTR) is uncommon as well, so let's use unlikely() for
> > the condition check in SLUB's and SLOB's kfree() to optimize for the
> > common case. SLAB has this already.
>
> I went through my current versions of slab/slub/slub and came up with this:
>
> diff -puN mm/slob.c~slub-slob-use-unlikely-for-kfreezero_or_null_ptr-check mm/slob.c
> --- a/mm/slob.c~slub-slob-use-unlikely-for-kfreezero_or_null_ptr-check
> +++ a/mm/slob.c
> @@ -360,7 +360,7 @@ static void slob_free(void *block, int s
> slobidx_t units;
> unsigned long flags;
>
> - if (ZERO_OR_NULL_PTR(block))
> + if (unlikely(ZERO_OR_NULL_PTR(block)))
btw this makes NO sense at all; gcc already defaults to assuming
unlikely if you check a pointer for NULL....
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