Re: [PATCH 1/3] drm/i915/execlists: Microoptimise execlists_cancel_port_request()

Chris Wilson
2017-09-25T13:08:12Z

Quoting Mika Kuoppala (2017-09-25 14:00:17)
> Chris Wilson <chris@chris-wilson.co.uk> writes:
>
> > Just rearrange the code slightly to trim the number of iterations
> > required.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> > drivers/gpu/drm/i915/intel_lrc.c | 17 ++++++++++-------
> > 1 file changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> > index 3623403a4f2d..2c07f3c08bd3 100644
> > --- a/drivers/gpu/drm/i915/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> > @@ -571,14 +571,17 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> > execlists_submit_ports(engine);
> > }
> >
> > -static void execlist_cancel_port_requests(struct intel_engine_execlists *execlists)
> > +static void
> > +execlist_cancel_port_requests(struct intel_engine_execlists *execlists)
> > {
> > - unsigned int i;
> > -
> > - for (i = 0; i < ARRAY_SIZE(execlists->port); i++)
> > - i915_gem_request_put(port_request(&execlists->port[i]));
> > + struct execlist_port *port = execlists->port;
> > + unsigned int num_ports = ARRAY_SIZE(execlists->port);
> >
> > - memset(execlists->port, 0, sizeof(execlists->port));
> > + while (num_ports-- && port_isset(port)) {
> > + i915_gem_request_put(port_request(port));
> > + memset(port, 0, sizeof(*port));
> > + port++;
> > + }
>
> I thought this to be more about the reset and thus memsetting
> everything would give us a clean plate. However now it matches
> more of what the function is about.

Right. It started off life as being memset everything on reset, but I
want to use it more actively, so wanted to trim it to only work over the
set ports.
-Chris