Re: [PATCH] mm : add check for the return value

[Minchan Kim <minchan.kim@gmail.com>]

On Mon, 04 Jan 2010 12:10:16 +0800
shijie8 <shijie8@gmail.com> wrote:

> 
> > I think it's not desirable to add new branch in hot-path even though
> > we could avoid that.
> >
> > How about this?
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 4e4b5b3..87976ad 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1244,6 +1244,9 @@ again:
> >          return page;
> >
> >   failed:
> >    
> you miss anther place where also  uses "goto failed".

Yes. It was just for showing my intention. :)

> > +       spin_lock(&zone->lock);
> > +       __mod_zone_page_state(zone, NR_FREE_PAGES, 1<<  order);
> > +       spin_unlock(&zone->lock);
> >          local_irq_restore(flags);
> >          put_cpu();
> >          return NULL;
> >
> >    
> I also thought  over your method before I sent the patch,  but there 
> already exits a
> "if (!page)" , I not sure whether my patch adds too much delay in hot-path.

Tend to agree. I don't object your patch. 

I think the branch itself could not a big deal but 'likely'. 

Why I suggest is that now 'if (!page)' don't have 'likely'.
As you know, 'likely' make the code relocate for reducing code footprint.

Why? It was just mistake or doesn't need it? 

I think Mel does know it. 

-- 
Kind regards,
Minchan Kim

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