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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DLvHS0z3; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB6D1606A31B for ; Fri, 23 Oct 2026 08:04:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DLvHS0z3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57F141F031E1; Fri, 23 Oct 2026 08:04:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792742660; bh=IdLhW5v/uXp4ejNif40TjF7Cr8YlsY2rrfu5zrwCz7c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=DLvHS0z3aZq5esQJCFYVnmr4BZd8HRgdUe7FpM8c/zwhoNvsqtTxGjMcmiUJ954iy 4/qivbqF8g3/ACcZlqnn7TNf7fVKzzyHmS80beVWwifppBXCr41RqxdOUVP0yvmsK4 z5dMIazWDzhhA6GBnOLndxrdRIbVWdl0R8wsiexT4ZvZYWXKiQNSOpnYySqtCl722M 2S1zVy7NeBI/Hlvcq6cT0Adjjwv2wnEW8/Tvwor0Cn8lYHtACdwi35eIJ+bwbjnrJ9 70xMSu1I8xSLZlTqeVgfBxKDJxrNtSZotA+PsWNANM9e7IrLI8p53uqS2R+a6A2QUM K7oqvPGi0nEqQ== Message-ID: Date: Fri, 23 Oct 2026 10:04:16 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 2/8] mm, slab: introduce slab_debug=N Content-Language: en-US To: Harry Yoo 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 References: <20260923-slub_tiny_rework-v1-0-a0e66d536eb5@kernel.org> <20260923-slub_tiny_rework-v1-2-a0e66d536eb5@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/24/26 16:48, 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) Yeah it doesn't change. Perhaps, later in the series I should consider what exactly slab_tiny=1 slab_debug=- shhould do. Hm. > 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] Hm that likely should not happen with =N, will adjust. > - Disable slab merging. Since this does not affect object metadata > layout, this could be excluded. Right, also we want merging with slab_tiny=1. Thanks!