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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49230a58becsm182335635e9.7.2026.06.17.15.04.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jun 2026 15:04:56 -0700 (PDT) Date: Wed, 17 Jun 2026 23:04:55 +0100 From: David Laight To: Aaron Tomlin Cc: akpm@linux-foundation.org, lance.yang@linux.dev, mhiramat@kernel.org, pmladek@suse.com, linux-kernel@vger.kernel.org, neelx@suse.com, sean@ashe.io, chjohnst@gmail.com, steve@abita.co, mproche@gmail.com, nick.lange@gmail.com Subject: Re: [PATCH] hung_task: Add per-round stack trace deduplication Message-ID: <20260617230455.73cff28d@pumpkin> In-Reply-To: <20260617184841.1447955-1-atomlin@atomlin.com> References: <20260617184841.1447955-1-atomlin@atomlin.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 17 Jun 2026 14:48:41 -0400 Aaron Tomlin wrote: > Currently, when multiple tasks hang in the exact same location (e.g., > such as severe contention for a mutex), khungtaskd indiscriminately > reports every single instance. This wastes ring buffer space with > identical stack traces up to the defined warning limit (i.e., > kernel.hung_task_warnings), obscuring the root cause without providing > any additional diagnostic value. > > Introduce a lightweight, hash-based stack trace deduplicator for > khungtaskd to ensure only unique stack traces are reported during > a single detection interval. How many different stacks do you need to suppress? Mostly wont it be 'the same as the last one'? So just a linear scan through a very small number of entries will largely DTRT. Much simpler code and a much smaller data footprint. David