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c=simple/simple; d=arm.com; s=foss; t=1789723322; bh=YXbg8h3QX0LMadHGqUmPe0199Ik27wuAwoICustn92g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CRc6En4owgRirjVFVR4Xi7k4EH/UqS925SavcyEn6s2SVlrryWaSnc0wN8NoROyWW y76nl7qrmR2OakFBMRGC0llWAeFBqZZr0fHquU3/J6n1gNaRDrJBOMG/aqFoIVJ7S1 fhtNVUhWRtl2QTEcq/Wn9m/1AbLWsqQ8QMRSETPw= Date: Fri, 18 Sep 2026 10:21:58 +0100 From: Catalin Marinas To: Breno Leitao Cc: Jonathan Corbet , Shuah Khan , Randy Dunlap , Andrew Morton , workflows@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: Re: [PATCH 3/3] mm: kmemleak: raise min_unref_scans to 3 for verbose auto-scan Message-ID: References: <20260917-b4-kmemleak-doc-v1-0-84fde6d1f749@debian.org> <20260917-b4-kmemleak-doc-v1-3-84fde6d1f749@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260917-b4-kmemleak-doc-v1-3-84fde6d1f749@debian.org> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 32722140006 X-Rspam-User: X-Stat-Signature: 3bckkpxxbbns4hkfh4irxan5irjbd5mf X-HE-Tag: 1789723323-95053 X-HE-Meta: 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 n8k1ocKs tHzgQazxMmEJQPDXwrfb84Izfz9fgkbRqDOdMR53yifJ8RQLlgZv9IlKJU3A1XRixJp/L7TC9CIv5+U1/8vjLl7ThCFDc0UjvbxK0XYhfPEJ8HFss8QSQ1OENupZguwCkw8by1f1hscnLep1CzQnH7wBu7/DZSWndFU8rWiai8scNHo240qR3fly1aE4ca8AFtaIskzD1QT4gEgD8esQyokZNMfYT0YQ/x/Wx5Gz97Dr7MlBD51x2Sb84GtU/Hl8KWUcYWlEXvo8sJ6AfrGsaRlnWRct4rqrakn6dvGSCGFbMYIEpgIV3FMnfjDjJ4Y5NAP+t6s/fFeHUSXevqcQ7erzf6RQbRZ+OZBN0LEMKpnvCmF0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 17, 2026 at 06:47:37AM -0700, Breno Leitao wrote: > CONFIG_DEBUG_KMEMLEAK_VERBOSE sends every report to the console, so a > transient false positive there is broadcast to whatever collects the > kernel log rather than sitting in the debugfs file until someone looks. > That asymmetry justifies being more conservative than the general case. > > Require one more consecutive unreferenced scan before reporting. The > only cost is that a genuine leak is reported one scan interval later > (600s by default); the value stays writable at run time through the > module parameter. > > Kernels without CONFIG_DEBUG_KMEMLEAK_VERBOSE keep reporting on the > first unreferenced scan. > > I've been running constant upstream kernel with > CONFIG_DEBUG_KMEMLEAK_VERBOSE set, and I am still seeing some rare false > positive, that goes away with min_unref_scans=3, so, making it the > default based on my heuristic. > > Signed-off-by: Breno Leitao Until someone comes up with a better idea to reduce the false positives, Reviewed-by: Catalin Marinas