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: 12701601 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9AF5EC4332F for ; Thu, 30 Dec 2021 19:16:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=D9oudbnkTvGD5BvRhpfocdBlwHRgHOrYFpilijt5w4w=; b=lkdpJuHljZ7sIx wFxlZbHvXqJZba2He1m98HSnpJHK6ta6WX1G2rMFh3XuDtfRhomeeZ2EVlWpARX8vnCVLSpXIFXjD CAKloPpSpyU3kMIXVPiYGY7m37lfaPBPQ1W5jmAGXngrTUS98of/HbG3KHj19c25ffPCHvrC6+gfY 5aOpbY5z83Kx3eYJrzuT0z2Qf24Jn1y75HINh8PpkV4agyz3SIn1h5A/BDqjAz24bzVDVJBFhkpMt cnOlBKB/Yp4cGhbxNFnAh+g7MoOXCLzTQ7XvKAnOMD3Hm7O+2H0sKdL96Uou7yMCAfwg1zNrIdbza LyjfX7nWmoLMvxIvxLVA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n30t4-004up5-2y; Thu, 30 Dec 2021 19:14:54 +0000 Received: from out0.migadu.com ([94.23.1.103]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1n30rC-004tml-Lz for linux-arm-kernel@lists.infradead.org; Thu, 30 Dec 2021 19:13:00 +0000 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211230_111258_908174_7EB43402 X-CRM114-Status: GOOD ( 12.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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