Re: [igt-dev] [PATCH i-g-t 7/7] benchmarks/gem_exec_fault: Add softpin mode to support gens with ppgtt

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Thu, 14 Oct 2021 20:31:03 -0700, Zbigniew Kempczyński wrote:
>
> On Thu, Oct 14, 2021 at 08:18:23PM -0700, Dixit, Ashutosh wrote:
> > On Thu, 14 Oct 2021 19:49:05 -0700, Zbigniew Kempczyński wrote:
> > >
> > > On Thu, Oct 14, 2021 at 01:07:37PM -0700, Dixit, Ashutosh wrote:
> > > > On Thu, 14 Oct 2021 01:19:17 -0700, Zbigniew Kempczyński wrote:
> > > > >
> > > > > @@ -127,9 +151,14 @@ static int loop(uint64_t size, unsigned ring, int reps, int ncpus,
> > > > >					obj.alignment = 0;
> > > > >					gem_execbuf(fd, &execbuf);
> > > > >
> > > > > -					/* fault out */
> > > > > -					obj.alignment = 1ull << 63;
> > > > > -					__gem_execbuf(fd, &execbuf);
> > > > > +					if (ahnd) {
> > > > > +						obj.offset = get_offset(ahnd, obj.handle, size, 0);
> > > > > +						obj.flags |= EXEC_OBJECT_PINNED | EXEC_OBJECT_SUPPORTS_48B_ADDRESS;
> > > > > +					} else {
> > > > > +						/* fault out */
> > > > > +						obj.alignment = 1ull << 63;
> > > > > +						__gem_execbuf(fd, &execbuf);
> > > > > +					}
> > > >
> > > > Bug above, __gem_execbuf should be moved out of the else {}.
> > >
> > > No, it shouldn't. Normal execbuf will lead to unbind/bind with new offset
> > > and no 'alignment' fault-out execbuf is necessary.
> >
> > Ah, you are right. Though in that case I think, if the loop has N
> > iterations, the number of binds is N and the number of unbinds will be (N -
> > 1). Is it worth fixing that? Basically I think we might need to add a bind
> > outside the first iteration of the loop so that we have an unbind in the
> > first iteration itself. Then we will have N binds and N unbinds I think.
>
> You're right, for softpin case we got N-1. But I don't think we want to
> compare results between alignment / softpin paths but for dedicated changes
> in the kernel. So then that missing unbind doesn't matter.

I thought it is benchmarking the time taken for N binds and N unbinds so
not too sure how much difference N binds and N-1 unbinds make. Anyway
please go ahead and merge if you think it's fine.

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>