Re: [PATCH 2/2] perf/x86/amd/uncore: Free counter slot by index

[sashiko-bot@kernel.org]

> amd_uncore_del() scans ctx->events[] from slot zero and attempts a
> compare-exchange until it finds the event.
> 
> amd_uncore_add() records the slot it claimed in event->hw.idx. Perf
> calls ->del() only after a successful ->add(), and the driver never
> moves an installed event between slots. The index therefore remains
> valid until deletion.
> 
> Use the recorded index directly and retain the compare-exchange
> ownership check. Warn if it fails, as that means the driver lost track
> of the slot.
> 
> Deleting all events from a full PMU with N counters now requires N
> compare-exchanges instead of N * (N + 1) / 2.
> 
> On a host running a production workload in the Meta fleet, amd_uncore_del()
> was called 56,575 times per second from mux rotation.
> 
> Cc: Sandipan Das <sandipan.das@amd.com>
> Signed-off-by: Usama Arif <usama.arif@linux.dev>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260921153108.2713179-1-usama.arif@linux.dev?part=2