[Intel-gfx] [PATCH v4] drm/i915/slpc: Optmize waitboost for SLPC

Vinay Belgaumkar
2022-10-22T00:25:50Z

Waitboost (when SLPC is enabled) results in a H2G message. This can result
in thousands of messages during a stress test and fill up an already full
CTB. There is no need to request for RP0 if boost_freq and the min softlimit
are the same.

v2: Add the tracing back, and check requested freq
in the worker thread (Tvrtko)
v3: Check requested freq in dec_waiters as well
v4: Only check min_softlimit against boost_freq. Limit this
optimization for server parts for now.

Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
---
drivers/gpu/drm/i915/gt/intel_rps.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index fc23c562d9b2..32e1f5dde5bb 100644
--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -1016,9 +1016,15 @@ void intel_rps_boost(struct i915_request *rq)
if (rps_uses_slpc(rps)) {
slpc = rps_to_slpc(rps);

+ if (slpc->min_freq_softlimit == slpc->boost_freq)
+ return;
+
/* Return if old value is non zero */
- if (!atomic_fetch_inc(&slpc->num_waiters))
+ if (!atomic_fetch_inc(&slpc->num_waiters)) {
+ GT_TRACE(rps_to_gt(rps), "boost fence:%llx:%llx\n",
+ rq->fence.context, rq->fence.seqno);
schedule_work(&slpc->boost_work);
+ }

return;
}
--
2.35.1