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b=HPY+OX1IFUI5BVqOQkfPERmKSAn/n4y6s4BtNXRKq+mgnhKm7zWaY6EBmB9tR4a29 bHEb4an9nQPrscOJq0VKAD100xzvna1ePl9GVCYhOv4K7FmSLaeCF4qvOMVrnFysha rWaH9SXY0O1+bUuDUIfMi3Wz75+mSGyeQ3djugLUJJORR09kB+mmq+tAoY4/0fG9rd drwzcZrA0CF9+lq12RQnEe1kd+9Bf8hGiJ/apsKOCspHffkVEaVnuOMgdaWSIwN25+ tRAnATzo6ouSxDVx6LTlYzAMVQ3274V8vSXx/fCczcehWM+y6qiX68vMNp8UJtvAJx szcjb8uHwnGFA== Date: Thu, 24 Sep 2026 16:39:33 +0100 From: Harry Yoo To: "Vlastimil Babka (SUSE)" Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Geert Uytterhoeven , Conor Dooley , Damien Le Moal , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kees Cook Subject: Re: [PATCH RFC 2/8] mm, slab: introduce slab_debug=N Message-ID: References: <20260923-slub_tiny_rework-v1-0-a0e66d536eb5@kernel.org> <20260923-slub_tiny_rework-v1-2-a0e66d536eb5@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: axy6ezo35tamy81a6gxtrmtfkf4cjory X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 9D0F0180005 X-HE-Tag: 1790264376-74900 X-HE-Meta: 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 o483sgDW 8uxXJazv93n3CTH8MfLITZSDEvbv7wtdDfWxXkWx4trJGyWJak9Tnt+sJJ+T4ggcj42kSwsiknDOQm2KJ6TJX1aKOtEoyQS1w4U6W7qrTpFq7mUoZIggwmwsUyYAr+7C1fYtr7M64XiKIPEsW7ciuTVsFwb9l9rscZpS6AZUxaADaCytX4Xlr/X8Rh1UyRqviT1l2xQtSAw7V27i/gm8MknuJTj8f6WZEeX/x79B5DRna3cYT1s5MEKr7WulJH7URCpM1N7mFW0zp/k1ZWsDmgqNx8NhxXW/2hHW/15PrwVYmO6k= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 24, 2026 at 03:48:43PM +0100, Harry Yoo wrote: > On Wed, Sep 23, 2026 at 05:45:07PM +0200, Vlastimil Babka (SUSE) wrote: > > Enabling slab_debug has the side-effect of disabling all percpu caching > > of objects (now via sheaves), which can be sometimes useful for saving > > memory for e.g. kdump kernels. To make this possible without the > > overhead (CPU or memory) of actual debugging options such as poisoning, > > introduce a No-op debug option that only forces the debugging slow paths > > and zero sheaf capacity. > > Just to clarify, the intended behavior of slab_debug=- still > does not change, right? (the name "No-op" could be confusing here I > guess) > > And My LLM flagged an issue here (that I reviewed) > > Implementing it as debug flag has a few side effects: > > - pointer hashing will be disabled unless hash_pointers=always is > specified. [+Cc: Kees] > > - Disable slab merging. Since this does not affect object metadata > layout, this could be excluded. excluded "from SLAB_NEVER_MERGE" Obviously it should be still part of SLAB_MERGE_SAME though.