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

Mika Kuoppala
2017-09-25T13:02:14Z

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.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

> }
>
> static void execlists_cancel_requests(struct intel_engine_cs *engine)
> @@ -625,7 +628,7 @@ static void execlists_cancel_requests(struct intel_engine_cs *engine)
>
> execlists->queue = RB_ROOT;
> execlists->first = NULL;
> - GEM_BUG_ON(port_isset(&execlists->port[0]));
> + GEM_BUG_ON(port_isset(execlists->port));
>
> /*
> * The port is checked prior to scheduling a tasklet, but
> --
> 2.14.1
>
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