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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01A25EB64DA for ; Mon, 10 Jul 2023 10:38:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 96EAF6B0075; Mon, 10 Jul 2023 06:38:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 900EF6B0078; Mon, 10 Jul 2023 06:38:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 798D46B007B; Mon, 10 Jul 2023 06:38:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 637056B0075 for ; Mon, 10 Jul 2023 06:38:23 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 26FC71A02ED for ; Mon, 10 Jul 2023 10:38:23 +0000 (UTC) X-FDA: 80995352886.21.702CAC0 Received: from mail-io1-f54.google.com (mail-io1-f54.google.com [209.85.166.54]) by imf29.hostedemail.com (Postfix) with ESMTP id 5BDE0120004 for ; Mon, 10 Jul 2023 10:38:21 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=ZfeBuOSd; spf=pass (imf29.hostedemail.com: domain of glider@google.com designates 209.85.166.54 as permitted sender) smtp.mailfrom=glider@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1688985501; a=rsa-sha256; cv=none; b=e/inmm0afN7mPj/VfVxXsYlUqh7hmq0WwZIljI0exuXvevvuXhZMY504PldjPLwzxNxVaI /oWAb7TwJCiRUXZSItBfW/9am/qM18uA4w6bXIlXG/1IwWU9WZoMEYa4oNd1nRzUSmdiU9 AwgNvW8GLXuS/ziabNl0Ir9PMq8VE1c= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=ZfeBuOSd; spf=pass (imf29.hostedemail.com: domain of glider@google.com designates 209.85.166.54 as permitted sender) smtp.mailfrom=glider@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688985501; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=hvz04yJSt5agLndtywybtJHsB7jWS+1+gKVSsWWw8q8=; b=d5Oz75KQ1Hln7kLK3QEJmqWs/HI4IqKrxrsrszAQDy4jDlpww2AoMm3QBo9AQi0EjaQrdN HQzB/78c9iykJM0vizovTLMTNfrZPMrVqG2y/VEIWXsUSJT/gsWolaD0T1izu9+xmutHHT b9ggs8FpZnXaxBE7Hf+7BWALZBhthNw= Received: by mail-io1-f54.google.com with SMTP id ca18e2360f4ac-785cbc5bfd2so214413139f.2 for ; Mon, 10 Jul 2023 03:38:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688985500; x=1691577500; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=hvz04yJSt5agLndtywybtJHsB7jWS+1+gKVSsWWw8q8=; b=ZfeBuOSdYbBlOpAuhNHZJi7BqVWFERjTyEFqrZqpYPyypLFucIAUo3RB41SWrv/fNy 6MQeOYsEhQX1N9AEnZsZhshl6efmEASygO1KUfuF7HCLMPjfnbqUMiHBw8EaKuNZHj2U ZcASuu/2lYL77GerjZ4Um80miQJ03HJjjK/Zi1rE1/wrztQ4Dhqi/lcFW71Dc+pKyBOt iixCNR9dUX0YM0n83hosROqtaIW3lpgFSs04PVQkDrwAIc7GN31MHsQa7TpCu6KbUUD1 zYdxalep44S/+wDCu0OdM37vejXarY7nz2wuEzGAFIXAjwl5sN0QHTA/4X1wazKUXAwe JpXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688985500; x=1691577500; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=hvz04yJSt5agLndtywybtJHsB7jWS+1+gKVSsWWw8q8=; b=EV/QVIN5ROD86CHErC8l0UN+yggG7Qf3bEuBru34ykojp4DxXiN2fuvgCYbe/jbOQG IELgPWO5eD6OieY1q/9Hs8q6XquUJi4DZcfgy0BzDGgWeYrp/h92qMq9wXa9SsAbDTYs jVmErc3z+1Mhw+hGl8rE8Iqwl3OfoqrSpNtFkK7S2Fa/naDgSUheJLAL0IB5ULmZQocJ MXGO/61QG9OnlznixxDB6GAP1hbZ0MaeYSb1FTERBYlT3KEIJ5mi+dSS6063O6iNBC7o 0Yp8rDnJWg+OzgcMbjwqTbpWDyA1TGf4xubd44s88A9VmhGS7KJLk2O+zm+zOW/T5Mrs 8/cQ== X-Gm-Message-State: ABy/qLZypumlZRAu9EGJAbUbZ2O7GWBtXvp800rM3BX3xkWAKiKg8tKU FzQk+KQUa/JtjRrRUyTCTCdIaIVsYseeu9kEnMJ8XQ== X-Google-Smtp-Source: APBJJlHV0c/RmEiHfQDPTa8JHUyb9BGshA7xPbLYwdygcLChbrq+ZTqXINPJJAdemOgkFW139l34UqIqekrgl+kvTSg= X-Received: by 2002:a5d:9448:0:b0:783:65ba:8614 with SMTP id x8-20020a5d9448000000b0078365ba8614mr11099647ior.10.1688985500443; Mon, 10 Jul 2023 03:38:20 -0700 (PDT) MIME-Version: 1.0 References: <20230710032714.26200-1-zhangpeng.00@bytedance.com> In-Reply-To: <20230710032714.26200-1-zhangpeng.00@bytedance.com> From: Alexander Potapenko Date: Mon, 10 Jul 2023 12:37:44 +0200 Message-ID: Subject: Re: [PATCH] mm: kfence: allocate kfence_metadata at runtime To: Peng Zhang Cc: elver@google.com, dvyukov@google.com, akpm@linux-foundation.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, muchun.song@linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5BDE0120004 X-Stat-Signature: g4gddcbprhajykc1snexd1h6m8yezkxf X-Rspam-User: X-HE-Tag: 1688985501-840950 X-HE-Meta: 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 8CSmSNvJ 58iT3IKPSpyH4dOH2S9jJIsaZbqsS/xZhvQL+QXE7cBBtd7ZUKt6nBNzhZlO1xBrjAm1IuBt1MIaQhikjErUrG0RVmNz8bdZcTMVULelBj23WpBRhO99lqYnc0Ddj07846vsAIvVGzV3J8997prz/id2KICsXfYZtxD3QGqztWDDbZ/E4AIKleO77lLbQbZal0Gi+9gWe1hYgqW2rdGrpBtUMDPPmFgsCrxiDMoJQgluokkBuxb6xT2NrteXrBfb1e/IrRuiRfl2lhBtVrZrB0X1l+AH8Vb7VscxOzzHiAx2EOBuRKxA9BgMVU8SpxwDFt90g7O64w6dzJ50= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000054, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 10, 2023 at 5:27=E2=80=AFAM 'Peng Zhang' via kasan-dev wrote: > > kfence_metadata is currently a static array. For the purpose of > allocating scalable __kfence_pool, we first change it to runtime > allocation of metadata. Since the size of an object of kfence_metadata > is 1160 bytes, we can save at least 72 pages (with default 256 objects) > without enabling kfence. > > Below is the numbers obtained in qemu (with default 256 objects). > before: Memory: 8134692K/8388080K available (3668K bss) > after: Memory: 8136740K/8388080K available (1620K bss) > More than expected, it saves 2MB memory. Do you have an understanding of where these 2MB come from? According to your calculations (which seem valid) the gain should be 290K, so either 2MB is irrelevant to your change (then these numbers should be omitted), or there's some hidden cost that we do not know about.