On Fri, 17 Aug 2007, Arjan van de Ven wrote:
>
> 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....
ZERO_OR_NULL_PTR() is not a check for NULL.
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