On 05/06/18 17:28, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-06-05 17:19:11)
We would like to make use of perf in Vulkan. The Vulkan API is much
lower level than OpenGL, with applications directly exposed to the
concept of command buffers (pretty much equivalent to our batch
buffers). In Vulkan, queries are always limited in scope to a command
buffer. In OpenGL, the lack of command buffer concept meant that
queries' duration could span multiple command buffers.
With that restriction gone in Vulkan, we would like to simplify
measuring performance just by measuring the deltas between the counter
snapshots written by 2 MI_RECORD_PERF_COUNT commands, rather than the
more complex scheme with currently have in the GL driver, using 2
MI_RECORD_PERF_COUNT commands and doing some post processing on the
stream of OA reports to remove any unrelated deltas in the OA stream.
Disabling preemption only apply to the context with which want to
query performance counters and is considered a privileged operation
(disabled by default).
and protected by CAP_SYS_ADMIN (give or take it requiring root
privilege to let an ordinary user set it themselves).
Please make that clear in the commit log for the likes of myself who
panicked at the mere thought of being able to stop preemption (because
it's an outright priority inversion). Note that this will not escape a
fast reset timer so the batch had better be short, or they will end up
being banned.
Sure, I thought people would be scared.
Adding it locally.
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 7d63c6d2f687..417ca93ea606 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2099,7 +2099,9 @@ static int gen8_emit_bb_start(struct i915_request *rq,
*
* That satisfies both the GPGPU w/a and our heavy-handed paranoia.
*/
- *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
+ *cs++ = MI_ARB_ON_OFF |
I'd prefer having it as a u32 enable/disable. Could it be intel_context
even, i.e. selectable on engine?
*cs++ = MI_ARB_ON_OFF | rq->hw_context->arb_enable;
Yeah, I just thought about putting it on the engine. Will do that too.
Right now it only make sense on the RCS anyway, that's where the OA unit
works.
Thanks,
-
Lionel
-Chris
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