On Fri, Aug 26, 2016 at 01:43:42PM +0300, Mika Kuoppala wrote:
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > On Fri, Aug 26, 2016 at 12:41:16PM +0300, Mika Kuoppala wrote:
> >> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> >>
> >> > Leave the more complicated request dequeueing to the tasklet and instead
> >> > just kick start the tasklet if we detect we are adding the first
> >> > request.
> >> >
> >> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> >> > ---
> >> > drivers/gpu/drm/i915/intel_lrc.c | 28 ++++------------------------
> >> > 1 file changed, 4 insertions(+), 24 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >> > index 6b49df4316f4..ca52b8e63305 100644
> >> > --- a/drivers/gpu/drm/i915/intel_lrc.c
> >> > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> >> > @@ -609,35 +609,15 @@ static void intel_lrc_irq_handler(unsigned long data)
> >> > static void execlists_submit_request(struct drm_i915_gem_request *request)
> >> > {
> >> > struct intel_engine_cs *engine = request->engine;
> >> > - struct drm_i915_gem_request *cursor;
> >> > - int num_elements = 0;
> >> >
> >> > spin_lock_bh(&engine->execlist_lock);
> >> >
> >> > - list_for_each_entry(cursor, &engine->execlist_queue, execlist_link)
> >> > - if (++num_elements > 2)
> >> > - break;
> >> > -
> >> > - if (num_elements > 2) {
> >> > - struct drm_i915_gem_request *tail_req;
> >> > -
> >> > - tail_req = list_last_entry(&engine->execlist_queue,
> >> > - struct drm_i915_gem_request,
> >> > - execlist_link);
> >> > -
> >> > - if (request->ctx == tail_req->ctx) {
> >> > - WARN(tail_req->elsp_submitted != 0,
> >> > - "More than 2 already-submitted reqs queued\n");
> >> > - list_del(&tail_req->execlist_link);
> >> > - i915_gem_request_put(tail_req);
> >> > - }
> >> > - }
> >> > -
> >> > i915_gem_request_get(request);
> >> > - list_add_tail(&request->execlist_link, &engine->execlist_queue);
> >> > request->ctx_hw_id = request->ctx->hw_id;
> >> > - if (num_elements == 0)
> >> > - execlists_unqueue(engine);
> >> > +
> >> > + list_add_tail(&request->execlist_link, &engine->execlist_queue);
> >> > + if (request->execlist_link.prev == &engine->execlist_queue)
> >>
> >> Why not list_first_entry()?
> >
> > Ah, because it's not as magic as I thought :)
> >
> > if (list_first_entry(&engine->execlist_queue,
> > struct drm_i915_gem_request,
> > execlist_link) == request)
> >
> > I think is reason enough.
>
> Agreed. Looked at
>
> if (list_is_singular(&engine->execlist_queue))
>
> but that it will add needless empty check.
>
> If that is abomination, just add comment that we need to resubmit
> if the list was empty.
>
> Without digging the list internals, the next reader also
> could be more happy with
>
> head->next == head->prev check.
As a temporary, we can use list_empty() before the add since we are
holding the spinlock.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
