From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 39464C44529 for ; Tue, 21 Jul 2026 15:41:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C8EC36B0098; Tue, 21 Jul 2026 11:41:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C40316B0099; Tue, 21 Jul 2026 11:41:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B2F816B009B; Tue, 21 Jul 2026 11:41:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 7E92F6B0098 for ; Tue, 21 Jul 2026 11:41:20 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 16FF91601CF for ; Tue, 21 Jul 2026 15:41:20 +0000 (UTC) X-FDA: 85013197920.10.CA18CEF Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf18.hostedemail.com (Postfix) with ESMTP id 71A5C1C0006 for ; Tue, 21 Jul 2026 15:41:18 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=NtrX8Fj7; spf=pass (imf18.hostedemail.com: domain of harry@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=harry@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784648478; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AI9xw2VxbQp7jX/B5YduqGMEsi6H2MQYTvtbRLDj+lQ=; b=CIGJkw/7AfZKtUbrypjgqhZty1u/qPiMqBSShu6wOy9A1+AIwPiGAwf8ub+zv0JX9+AuFf DyrxXzUUzh1uN7vSobiQ2ZwrLwf1CMzv99HGbTvOvBe6RXJnR0xFp2jb5XLQ4OYgYD7yVS l4wcySAPVKlHTxAbZAPHCStvRA+SUZk= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784648478; b=zpar/pg4FPosL2sis+d5bRkEV+1IzbNbF0f2FY4S5rQ7LCZK/YTi1Se40akO7qYfkhMM07 Q7qkWDcHAHQFYwyoQ9dtbJdNFemDWL5J6nc0LhZ9WXeqQPulK1L42GbiotPHgcXzhOeuyd izYU/yRPtzt5yCYEU/R8BB47mDabj28= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=NtrX8Fj7; spf=pass (imf18.hostedemail.com: domain of harry@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=harry@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id D51CA60054; Tue, 21 Jul 2026 15:41:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1312E1F000E9; Tue, 21 Jul 2026 15:41:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784648477; bh=AI9xw2VxbQp7jX/B5YduqGMEsi6H2MQYTvtbRLDj+lQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NtrX8Fj7MU5zwfg83ZUMZfEGaN6yiGQFBNo9V9EorL498LCl6y+uUXPMaew6uQ814 xtTYLI8WOBNCHHVSqPhwBh2fXbW3bE/a5lkOiNrco9fge8qyNJ/VnnyS7pkKM1k2xe onZdI0uZk+PMrMcuhJ3A4cf9UaWO+L0m+imJ06ogOSUYiyczDvWgioLzgTt56qzPVN zKTOPa8GJTEhkGtqjT+gbZLyme5ItgNld/9LEJEFa6Q04EuUZcNGxFoxtTQOkVqg/p eOtSLf+4IVFD3piDBW8rTs+31ExAcMsWX003NIwQ+J9+Wl20w+NVI5P46zlnBc7E8w wC+1cblY0O4qQ== Message-ID: <31e637da-1ef2-412f-9c4a-26b720d7c74a@kernel.org> Date: Wed, 22 Jul 2026 00:41:10 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/13] mm/slab: skip kfence objects in allocation profiling To: "Vlastimil Babka (SUSE)" , Suren Baghdasaryan Cc: Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <20260720-b4-objext_split-v2-0-2fa7c6f60dbe@kernel.org> <20260720-b4-objext_split-v2-1-2fa7c6f60dbe@kernel.org> <96468090-6b31-4f78-a813-c5729b53aa3d@kernel.org> Content-Language: en-US From: Harry Yoo In-Reply-To: <96468090-6b31-4f78-a813-c5729b53aa3d@kernel.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------lihAPi6O8DUJyauCGzEd0pPf" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 71A5C1C0006 X-Stat-Signature: osac6ihotufoy9mb6356iaati9ijfmg5 X-Rspam-User: X-HE-Tag: 1784648478-705363 X-HE-Meta: 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 u0HQOmeP 3CK9qobN4Oa/Y+1ouMl9fNubTO3nBxuVTKZnIyzM6ufLj7jL/ns1elCMOt6Ma8KzfHZs48ZEDxEybzmyeSo3opqm3mUXUeECRh7AUfp9r+mMd4EYOvEHs1F1YSyBvJ9ys7ADy5E2Iwg9Cw/rLTDIYW/c75SR6yKNtdFs+zVOMS9YX1GFybs+Komwy5XbBbCwe0Sjws7P9oLmEznKRVsuMq+4797ZOzh++iyYB51ALEZKYbrm9iq5Fe57yRk/pa5Frs8s93KRChN04171HJDX6sADp90Q80XcM/WCAr5o6/wafC5kEIEcUGTr6GRf3KgVcQv+pxt10rCuyXMjlOsRuDYwlAV4xHd2Aom6yVt+PZpNuh4Dm/YqOIdnWxNxLvILpt6PrjvTcFn6QZ4FXx5/ZWzEw7azIuEUfJ6EkD5Rz6G46V2yUGA0z15C2hKPbYn1jxst8abxt3Gp8fQQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------lihAPi6O8DUJyauCGzEd0pPf Content-Type: multipart/mixed; boundary="------------DI7QtXXAQSwUVNu604OE0Y40"; protected-headers="v1" From: Harry Yoo To: "Vlastimil Babka (SUSE)" , Suren Baghdasaryan Cc: Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Message-ID: <31e637da-1ef2-412f-9c4a-26b720d7c74a@kernel.org> Subject: Re: [PATCH v2 01/13] mm/slab: skip kfence objects in allocation profiling References: <20260720-b4-objext_split-v2-0-2fa7c6f60dbe@kernel.org> <20260720-b4-objext_split-v2-1-2fa7c6f60dbe@kernel.org> <96468090-6b31-4f78-a813-c5729b53aa3d@kernel.org> In-Reply-To: <96468090-6b31-4f78-a813-c5729b53aa3d@kernel.org> --------------DI7QtXXAQSwUVNu604OE0Y40 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 7/21/26 6:20 PM, Vlastimil Babka (SUSE) wrote: > On 7/21/26 07:43, Harry Yoo wrote: >> On 7/20/26 11:16 PM, Vlastimil Babka (SUSE) wrote: >>> struct kfence_metadata only contains struct slabobj_ext with >>> CONFIG_MEMCG, which is then used for the "fake" slab's obj_exts field= =2E >>> If CONFIG_MEMCG is enabled, the struct can also end up used for memor= y >>> allocation profiling. If CONFIG_MEMCG is disabled but profiling is >>> enabled, it will end up allocating its obj_exts via >>> prepare_slab_obj_exts_hook() and assigning them to the fake struct sl= ab. >>> These will probably then never be freed. >>> >>> So things sorta work, but not always in the intended and optimal way.= >>> The upcoming changes to slabobj_ext layout would additionally need a >>> proper refactoring to keep working. >>> >>> However, there's little benefit in accounting KFENCE objects. KFENCE >>> allocations are rare and there can be only CONFIG_KFENCE_NUM_OBJECTS >>> (default to 255) outstanding ones at any time. For any callsite >>> prominent enough in the memory allocation profiling stats, allocation= s >>> served from KFENCE will be lost in the noise. >> >> For a similar reason I wonder if we can drop obj_exts completely. =2E..for kfence objects! > To make it clear, you mean kfence objects wouldn't have objcg accountin= g and > would essentially behave as if obj_exts for them could not be allocated= =2E Haha, right. Thanks for clarifying. >> The idea that kfence objects might have different slabobj_ext layout >> isn't really worth the extra complexity if we have very limited amount= >> of kfence objects. The amount of objects that escape memcg accounting >> will be quite limited. >=20 > Indeed. I think the main point wasn't to have everything accounted, but= to > avoid specially cased kfence paths. > But I think this would probably just require adding is_kfence checks to= > objext allocation paths to fail them, so that's manageable. Agreed. > Should perhaps > allow moving some of the checks added by this patch to more generic sha= red > places. Which places did you mean by 'more generic shared places'? --=20 Cheers, Harry / Hyeonggon --------------DI7QtXXAQSwUVNu604OE0Y40-- --------------lihAPi6O8DUJyauCGzEd0pPf Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature.asc" -----BEGIN PGP SIGNATURE----- iHUEARYKAB0WIQQQ1ub6gR5ogjaKRmOGXBN6rc5S1gUCal+TFgAKCRCGXBN6rc5S 1p1pAP0XU9L5CZnX3R1WlPuTzkAElnqLx3SBYNykv6t/dWnyMAD9HX2ksCXwGe4N oQmhmLj0qHcHsgUqb1WXUMWF6EyZBwE= =EJeX -----END PGP SIGNATURE----- --------------lihAPi6O8DUJyauCGzEd0pPf--