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Peter Anvin" , Arnd Bergmann , Dennis Zhou , Tejun Heo , Christoph Lameter , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, virtualization@lists.linux.dev, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v6 0/7] locking: contended_release tracepoint instrumentation Message-ID: <20260513192605.GA2545104@noisy.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D4652C0003 X-Stat-Signature: t6ucjwyyxnb3qn7fp8i9nob3uw9igmoc X-HE-Tag: 1778700376-654171 X-HE-Meta: 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 E48nyOGU q9xd6ldH9qQNwEuGgxSCYWNrJ1v2nF7kH/2sU8Ue06EOlXf1sCVJEbY9cV3uAZdnIM1MhRi6/SoWJ0DQhWfdRAqpYpF9yWvn7ss6zkVu0U1EXbUVo9bZzBedbyD51H7BJ9EcqDVlmhX+33Y4R8C1LxJ6CcxF8bJvWjGqgXJiJXaRsVRHLt1lYRdye+HDhjPA8QjY5uf6epF13Fch9yKBq4dh1C6hOUPxBl8xvAJo1sVMEWQECHJokYMwUYFzNWz/B4biNqwZaRhqbtz/w3NcCucoLAbHKI69YGEN8 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, May 05, 2026 at 05:09:29PM +0000, Dmitry Ilvokhin wrote: > This series adds a contended_release tracepoint that fires on the > holder side when a lock with waiters is released. This provides: > > - Hold time estimation: when the holder's own acquisition was > contended, its contention_end (acquisition) and contended_release > can be correlated to measure how long the lock was held under > contention. > > - The holder's stack at release time, which may differ from what perf lock > contention --lock-owner captures if the holder does significant work between > the waiter's arrival and the unlock. > > Note: for reader/writer locks, the tracepoint fires for every reader > releasing while a writer is waiting, not only for the last reader. And for qspinlock. I am really not sure this is worth the overhead for qspinlock / rwlock.