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b=0odt9qskdT0KVfFDu2lB1AstQjY0/yTp3t9erG637/acag9gjkBcAroCrGjXaphX4 yCeeiCY1laOyYchoh7XQ+nX/Tx1bbYVIk8osY5vBFqLTx41EfQ8bOyKTCTZTWtrRB9 HJ6WYRiqeB41Cr1Bmaug0k9DGtIfhba8wy+dVbww= Date: Sat, 21 Mar 2026 17:10:02 -0700 From: Andrew Morton To: Dmitry Ilvokhin Cc: Arnd Bergmann , Dennis Zhou , Tejun Heo , Christoph Lameter , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v3 0/4] locking: contended_release tracepoint instrumentation Message-Id: <20260321171002.013ee5a9d8c789e2a4a53afc@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: CA32B20007 X-Rspamd-Server: rspam08 X-Stat-Signature: nhfsm3buc13jc19x3c75ysmdrzgwco6j X-HE-Tag: 1774138204-213900 X-HE-Meta: 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 x7s3o7bt LhK5n1uovEvVM5aE1jYNTzkeiCyloXVdPFVDb8XL9RLSJEOvvhXGZFCDVzbAigQfuLMGNgEZl6JXhhQvB2f7Tz6MMli+p0LXg/3jZJm1J3qnLP6UcUoEhtE34RbkgL/wlOQ1UdD6U5wxQDj02UtDuLcwRYWNeMaAJJRA7htKXHC6v7beEWzJegFgPdOCpoUCPDL2O04fV1aO8pFX8c1V8D1wl6l2jX+3prdH5hgGbFKOWZUJCWBtjvuNZKClxTgbJNJem13WvEJNJL191SZIi9qUjoJCna5oF+F5t0l4URYR7i9CrFrArw2PQzP3ko9R2ps/G4ptkAAg7CcmCUvNMgvxez/NBbN/8YghWartM0zph1CeNoY/4rPEBmLCOajgBdyp5JMg4JNyc+9leGA5hYzqOqj7vsScL/HLy Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 18 Mar 2026 18:45:17 +0000 Dmitry Ilvokhin wrote: > The existing contention_begin/contention_end tracepoints fire on the > waiter side. The lock holder's identity and stack can be captured at > contention_begin time (e.g. perf lock contention --lock-owner), but > this reflects the holder's state when a waiter arrives, not when the > lock is actually released. > > 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. > > The series is structured as follows: > > 1. Remove unnecessary linux/sched.h include from trace/events/lock.h. > 2. Extract __percpu_up_read() out of the inline percpu_up_read() to > avoid binary size increase from adding a tracepoint. > 3. Add contended_release tracepoint and instrument sleepable locks: > mutex, rtmutex, semaphore, rwsem, percpu-rwsem, and rwbase_rt. AI review: https://sashiko.dev/#/patchset/cover.1773858853.git.d@ilvokhin.com