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Date: Fri, 30 Aug 2024 10:23:52 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>, Kan Liang <kan.liang@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	linux-perf-users@vger.kernel.org, Song Liu <song@kernel.org>,
	bpf@vger.kernel.org, Xi Wang <xii@google.com>
Subject: Re: [PATCH] perf lock contention: Fix spinlock and rwlock accounting
Message-ID: <ZtHH6JcfNUBAQAen@x1>
References: <20240828052953.1445862-1-namhyung@kernel.org>
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In-Reply-To: <20240828052953.1445862-1-namhyung@kernel.org>

On Tue, Aug 27, 2024 at 10:29:53PM -0700, Namhyung Kim wrote:
> The spinlock and rwlock use a single-element per-cpu array to track
> current locks due to performance reason.  But this means the key is
> always available and it cannot simply account lock stats in the array
> because some of them are invalid.
> 
> In fact, the contention_end() program in the BPF invalidates the entry
> by setting the 'lock' value to 0 instead of deleting the entry for the
> hashmap.  So it should skip entries with the lock value of 0 in the
> account_end_timestamp().

Thanks, applied to perf-tools-next,

- Arnaldo