On 03/03/2021 23:28, Umesh Nerlige Ramappa wrote:
Perf measurements rely on CPU and engine timestamps to correlate events of interest across these time domains. Current mechanisms get these timestamps separately and the calculated delta between these timestamps lack enough accuracy. To improve the accuracy of these time measurements to within a few us, add a query that returns the engine and cpu timestamps captured as close to each other as possible. v2: (Tvrtko) - document clock reference used - return cpu timestamp always - capture cpu time just before lower dword of cs timestamp v3: (Chris) - use uncore-rpm - use __query_cs_timestamp helper v4: (Lionel) - Kernel perf subsytem allows users to specify the clock id to be used in perf_event_open. This clock id is used by the perf subsystem to return the appropriate cpu timestamp in perf events. Similarly, let the user pass the clockid to this query so that cpu timestamp corresponds to the clock id requested. v5: (Tvrtko) - Use normal ktime accessors instead of fast versions - Add more uApi documentation v6: (Lionel) - Move switch out of spinlock v7: (Chris) - cs_timestamp is a misnomer, use cs_cycles instead - return the cs cycle frequency as well in the query v8: - Add platform and engine specific checks v9: (Lionel) - Return 2 cpu timestamps in the query - captured before and after the register read Signed-off-by: Umesh Nerlige Ramappa<umesh.nerlige.ramappa@xxxxxxxxx> --- drivers/gpu/drm/i915/i915_query.c | 144 ++++++++++++++++++++++++++++++
FYI, the MR for Mesa : https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9407
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