From patchwork Thu Dec 30 19:12:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: andrey.konovalov@linux.dev X-Patchwork-Id: 12701595 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 5A931C433F5 for ; Thu, 30 Dec 2021 19:13:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C99EE6B0083; Thu, 30 Dec 2021 14:12:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BFAF06B0085; Thu, 30 Dec 2021 14:12:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9FD7F6B0088; Thu, 30 Dec 2021 14:12:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0141.hostedemail.com [216.40.44.141]) by kanga.kvack.org (Postfix) with ESMTP id 837916B0085 for ; Thu, 30 Dec 2021 14:12:53 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 45691180EB715 for ; Thu, 30 Dec 2021 19:12:53 +0000 (UTC) X-FDA: 78975407826.17.9E0D5C7 Received: from out0.migadu.com (out0.migadu.com [94.23.1.103]) by imf08.hostedemail.com (Postfix) with ESMTP id F3010160005 for ; Thu, 30 Dec 2021 19:12:41 +0000 (UTC) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1640891571; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=C7bL1Zr1naNl/Uo665wUTq0llGclMt9lfTghUSLQOMw=; b=VjUsadY10wVNgk5lXJf6EPVC01JU+PVX6X7U0/I6zySRYE9zmGB+n8D8czFGxnpysOY9sU XpmYkGqFnBKyKVkmc17yCUmYsJdadoIIFLVqj2QJGQKM+1AbU8fkhhKpYH3Rt9gMC5fLLw vJwvx3N8KtgDB064e+SZbyF49uE1Cm4= From: andrey.konovalov@linux.dev To: Andrew Morton Cc: Andrey Konovalov , Marco Elver , Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, linux-mm@kvack.org, Vincenzo Frascino , Catalin Marinas , Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, Peter Collingbourne , Evgenii Stepanov , linux-kernel@vger.kernel.org, Andrey Konovalov Subject: [PATCH mm v5 07/39] mm: clarify __GFP_ZEROTAGS comment Date: Thu, 30 Dec 2021 20:12:09 +0100 Message-Id: <4ef9f470c0d41437d7a2a111e2c739957f49ee39.1640891329.git.andreyknvl@google.com> In-Reply-To: References: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=VjUsadY1; spf=pass (imf08.hostedemail.com: domain of andrey.konovalov@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=andrey.konovalov@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: F3010160005 X-Stat-Signature: uc4uokbi9ojh1xsgm7788njn1p3o4wqk X-HE-Tag: 1640891561-659738 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: From: Andrey Konovalov __GFP_ZEROTAGS is intended as an optimization: if memory is zeroed during allocation, it's possible to set memory tags at the same time with little performance impact. Clarify this intention of __GFP_ZEROTAGS in the comment. Signed-off-by: Andrey Konovalov --- Changes v4->v5: - Mention optimization intention in the comment. --- include/linux/gfp.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 5f893d994dcd..19e55f3fdd04 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -228,8 +228,10 @@ struct vm_area_struct; * * %__GFP_ZERO returns a zeroed page on success. * - * %__GFP_ZEROTAGS returns a page with zeroed memory tags on success, if - * __GFP_ZERO is set. + * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself + * is being zeroed (either via __GFP_ZERO or via init_on_alloc). This flag is + * intended for optimization: setting memory tags at the same time as zeroing + * memory has minimal additional performace impact. * * %__GFP_SKIP_KASAN_POISON returns a page which does not need to be poisoned * on deallocation. Typically used for userspace pages. Currently only has an