perf/x86/amd/uncore: Use hrtimer for handling overflows

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Uncore counters do not provide mechanisms like interrupts to report
overflows and the accumulated user-visible count is incorrect if there
is more than one overflow between two successive read requests for the
same event because the value of prev_count goes out-of-date for
calculating the correct delta.

To avoid this, start a hrtimer to periodically initiate a pmu->read() of
the active counters for keeping prev_count up-to-date. It should be
noted that the hrtimer duration should be lesser than the shortest time
it takes for a counter to overflow for this approach to be effective.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/8ecf5fe20452da1cd19cf3ff4954d3e7c5137468.1744906694.git.sandipan.das@amd.com

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Sandipan Das 2025-04-18 09:13:01 +05:30 • committed by Ingo Molnar

parent 05c9b0cbe4

commit 6d937e044b

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arch/x86/events/amd/uncore.c

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