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 4EAB8C61DA4 for ; Thu, 9 Mar 2023 21:36:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D43456B0072; Thu, 9 Mar 2023 16:36:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CF3626B0074; Thu, 9 Mar 2023 16:36:16 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BBB0D280001; Thu, 9 Mar 2023 16:36:16 -0500 (EST) 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 AB9EE6B0072 for ; Thu, 9 Mar 2023 16:36:16 -0500 (EST) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 7A9D680430 for ; Thu, 9 Mar 2023 21:36:16 +0000 (UTC) X-FDA: 80550668352.28.DD118C7 Received: from mail-yw1-f178.google.com (mail-yw1-f178.google.com [209.85.128.178]) by imf26.hostedemail.com (Postfix) with ESMTP id B0DCF140007 for ; Thu, 9 Mar 2023 21:36:14 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=VnZTCI1O; spf=pass (imf26.hostedemail.com: domain of pcc@google.com designates 209.85.128.178 as permitted sender) smtp.mailfrom=pcc@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=1678397774; 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=PFnIpAyFi7KEE0nQFD6hvfwa5ttoKe86kwhnOw55/ZU=; b=LhoKpeHLKEEDbgIdXCBc5b6YFwvQJRldVstUcg9o4DKYUVKeHPcrEMxxE5lOJd2dCTf1bx c8McK2mGYLW6fhPKcpKP3cDgUQBfQlpJn03wG/vMyHnXmF+1BhAPi9JdrJGHcsEUeO66Hl SB/C2teckUYTB0UiMj0zRGbfwCAhnvM= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=VnZTCI1O; spf=pass (imf26.hostedemail.com: domain of pcc@google.com designates 209.85.128.178 as permitted sender) smtp.mailfrom=pcc@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678397774; a=rsa-sha256; cv=none; b=FGfaCzU23bf21LdVKAhYfc1NyqhiQpd69mbdkZbPDeBxHXCbFG5ZSyCqSb7FfYuOTBi9BB bXt/OVRfy2MHfC4P9uwT4oMaJ2el8gw3JJ3tGlEH1szLFvwPqT4f4VtexE4vqqJwRI7Ttl XRFC3s5dv2i/cH3lvllcdeVyMPCNhQo= Received: by mail-yw1-f178.google.com with SMTP id 00721157ae682-536be69eadfso60795257b3.1 for ; Thu, 09 Mar 2023 13:36:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1678397773; 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=PFnIpAyFi7KEE0nQFD6hvfwa5ttoKe86kwhnOw55/ZU=; b=VnZTCI1OG2ybp+DVQPhYDlJZxoHrTSn1SGD+EKOSP+tiVtsriqGK3Wu6ruHYY1pY/q 34eKL/jlCcUpMBncmj5tu3hzBHiIWsAnMVmMrQJfq6J04pISSiUxcu+jVVcO5U/uR7mk n3MKJ9JiXwHUXxPRGCbXYcEJt2U2D8NpoJ/KlsfSDuKSsj4naDLtvrFhicMEeb+0eiZl EDL8JJFGYt8jYxadX+tMn+Nidyew06w65UP5VLTThiEbV037I0/6ZFx8/NnePvpQRBBh eGJt+oNEi88TM1zrDt5T/STfcj9LlZqHxCWpSriEXOWH5vCPUBOS1zvek1N7aGEvjlI3 7vpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678397773; 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=PFnIpAyFi7KEE0nQFD6hvfwa5ttoKe86kwhnOw55/ZU=; b=WgPU3ujHRx3rjQE64P7+9+2vQNpBMgoC7o2yb0xfwhm8xDxojOedrVyo0/Tqrkpo5C NwdgccmkgEogkv4G220NBL3jw9tRTh/qk+Xmq7tTIa9yIzzCO4vm6X4/aKkaZkyfwMEP tJDeJpzSn72P1ejYC82MBK1exK/cEP6RcPGFyLQkL1knftJu1PU1SswyCLrLg1o4TTe/ V3psOrDNIu7DMeSnut7n5iXkQASNw/0LZILJ0d7AhhfkzrjAwK+wr/GN7uXN2xSA0Zf7 2vkycwZaXmJgOK5/Z4m95X9Q7F2vpSRUIkHMJ/T87LM2YxVa1+uoWuS3bPiQSEr+au7q P1LA== X-Gm-Message-State: AO0yUKUw6mfxMs8/0OPtFB0t09wFPoK/Rxwq03DjOuGLt25J9Od4cVFn sGn9z+AihyWuEWazuiScp8KZVHq6bNuDYS3y43AjvA== X-Google-Smtp-Source: AK7set81cPx++J8MDz2wFdv3aePYvK3Oo6i+9UbDfeOXLVptbDo7DEqL78MNnpcuOPV+QL+R/7pmNH+t2iq/nwNa3I0= X-Received: by 2002:a81:af46:0:b0:53c:70c5:45d9 with SMTP id x6-20020a81af46000000b0053c70c545d9mr14455374ywj.2.1678397773576; Thu, 09 Mar 2023 13:36:13 -0800 (PST) MIME-Version: 1.0 References: <20230301003545.282859-1-pcc@google.com> <20230301003545.282859-2-pcc@google.com> <20230308174608.e66ed98c97ea29934d99c596@linux-foundation.org> In-Reply-To: <20230308174608.e66ed98c97ea29934d99c596@linux-foundation.org> From: Peter Collingbourne Date: Thu, 9 Mar 2023 13:36:02 -0800 Message-ID: Subject: Re: [PATCH v3 1/2] Revert "kasan: drop skip_kasan_poison variable in free_pages_prepare" To: Andrew Morton Cc: catalin.marinas@arm.com, andreyknvl@gmail.com, linux-mm@kvack.org, kasan-dev@googlegroups.com, ryabinin.a.a@gmail.com, linux-arm-kernel@lists.infradead.org, vincenzo.frascino@arm.com, will@kernel.org, eugenis@google.com, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: qjr9byhbqknpcexs4rues1nkxsexoenk X-Rspam-User: X-Rspamd-Queue-Id: B0DCF140007 X-Rspamd-Server: rspam06 X-HE-Tag: 1678397774-454456 X-HE-Meta: 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 ryOnkz2v 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Mar 8, 2023 at 5:46=E2=80=AFPM Andrew Morton wrote: > > On Tue, 28 Feb 2023 16:35:44 -0800 Peter Collingbourne w= rote: > > > This reverts commit 487a32ec24be819e747af8c2ab0d5c515508086a. > > > > The should_skip_kasan_poison() function reads the PG_skip_kasan_poison > > flag from page->flags. However, this line of code in free_pages_prepare= (): > > > > page->flags &=3D ~PAGE_FLAGS_CHECK_AT_PREP; > > > > clears most of page->flags, including PG_skip_kasan_poison, before call= ing > > should_skip_kasan_poison(), which meant that it would never return true > > as a result of the page flag being set. Therefore, fix the code to call > > should_skip_kasan_poison() before clearing the flags, as we were doing > > before the reverted patch. > > What are the user visible effects of this change? > > > Cc: # 6.1 > > Especially if it's cc:stable. This fixes a measurable performance regression introduced in the reverted commit, where munmap() takes longer than intended if HW tags KASAN is supported and enabled at runtime. Without this patch, we see a single-digit percentage performance regression in a particular mmap()-heavy benchmark when enabling HW tags KASAN, and with the patch, there is no statistically significant performance impact when enabling HW tags KASAN. That can be added as a paragraph to the end of my commit message, or I can send a v4 if you prefer. Peter