Re: [PATCH 10/10] powerpc: remove address space overrides using set_fs()

[Christophe Leroy]

Le 02/09/2020 à 14:36, Christoph Hellwig a écrit :
> On Wed, Sep 02, 2020 at 08:15:12AM +0200, Christophe Leroy wrote:
> > > -		return 0;
> > > -	return (size == 0 || size - 1 <= seg.seg - addr);
> > > +	if (addr >= TASK_SIZE_MAX)
> > > +		return false;
> > > +	if (size == 0)
> > > +		return false;
> >
> > __access_ok() was returning true when size == 0 up to now. Any reason to
> > return false now ?
>
> No, this is accidental and broken.  Can you re-run your benchmark with
> this fixed?

With this fix, I get

root@vgoippro:~# time dd if=/dev/zero of=/dev/null count=1M
1048576+0 records in
1048576+0 records out
536870912 bytes (512.0MB) copied, 6.776327 seconds, 75.6MB/s
real    0m 6.78s
user    0m 1.64s
sys     0m 5.13s

That's still far from the 91.7MB/s I get with 5.9-rc2, but better than 
the 65.8MB/s I got yesterday with your series. Still some way to go thought.

Christophe