Re: [PATCH v4 1/5] powerpc/mm/slice: Remove intermediate bitmap copy

[Christophe LEROY]

Le 10/02/2018 Ã 15:43, Nicholas Piggin a ÃcritÂ:
> On Sat, 10 Feb 2018 13:54:25 +0100 (CET)
> Christophe Leroy <christophe.leroy@xxxxxx> wrote:
>
> > bitmap_or() and bitmap_andnot() can work properly with dst identical
> > to src1 or src2. There is no need of an intermediate result bitmap
> > that is copied back to dst in a second step.
>
> Everyone seems to be working on the slice code all of a sudden. I
> had the same change in my series I just posted, but I didn't notice
> this one of yours earlier, and it's better split out, so this is
> fine by me.

Thanks,

I had a quick look at your serie, it looks promising.

The main purpose of mine is to allow the use of slies on the 8xx in 
order to fix a hugepage related bug.

Your serie is performance oriented and seems nice, indeed I should have 
noticed that it was passing huge structures instead of pointers to 
subfunctions. I will look at your serie more in details next week.

Christophe


> Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx>
>
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> > ---
> >   v2: New in v2
> >   v3: patch moved up front of the serie to avoid ephemeral slice_bitmap_copy() function in following patch
> >   v4: No change
> >
> >   arch/powerpc/mm/slice.c | 12 ++++--------
> >   1 file changed, 4 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> > index 23ec2c5e3b78..98b53d48968f 100644
> > --- a/arch/powerpc/mm/slice.c
> > +++ b/arch/powerpc/mm/slice.c
> > @@ -388,21 +388,17 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
> >   
> >   static inline void slice_or_mask(struct slice_mask *dst, struct slice_mask *src)
> >   {
> > -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> > -
> >   	dst->low_slices |= src->low_slices;
> > -	bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> > -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
> > +	bitmap_or(dst->high_slices, dst->high_slices, src->high_slices,
> > +		  SLICE_NUM_HIGH);
> >   }
> >   
> >   static inline void slice_andnot_mask(struct slice_mask *dst, struct slice_mask *src)
> >   {
> > -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> > -
> >   	dst->low_slices &= ~src->low_slices;
> >   
> > -	bitmap_andnot(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> > -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
> > +	bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
> > +		      SLICE_NUM_HIGH);
> >   }
> >   
> >   #ifdef CONFIG_PPC_64K_PAGES