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 X-Spam-Level: X-Spam-Status: No, score=-13.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27742C433DF for ; Thu, 23 Jul 2020 08:53:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08D8720888 for ; Thu, 23 Jul 2020 08:53:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728222AbgGWIxa (ORCPT ); Thu, 23 Jul 2020 04:53:30 -0400 Received: from foss.arm.com ([217.140.110.172]:42008 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726177AbgGWIxa (ORCPT ); Thu, 23 Jul 2020 04:53:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B9ED1D6E; Thu, 23 Jul 2020 01:53:28 -0700 (PDT) Received: from [10.163.85.73] (unknown [10.163.85.73]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8E46D3F66F; Thu, 23 Jul 2020 01:53:26 -0700 (PDT) Subject: Re: [PATCH v2 2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry() To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, mike.kravetz@oracle.com, david@redhat.com, akpm@linux-foundation.org References: <20200723032248.24772-1-bhe@redhat.com> <20200723032248.24772-3-bhe@redhat.com> <20200723061437.GQ32539@MiWiFi-R3L-srv> From: Anshuman Khandual Message-ID: <7c0d19e9-4f90-9f74-d364-4d877ccf67f9@arm.com> Date: Thu, 23 Jul 2020 14:22:58 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200723061437.GQ32539@MiWiFi-R3L-srv> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/23/2020 11:44 AM, Baoquan He wrote: > On 07/23/20 at 10:36am, Anshuman Khandual wrote: >> >> >> On 07/23/2020 08:52 AM, Baoquan He wrote: >>> The checking is_migration_entry() and is_hwpoison_entry() are stricter >>> than non_swap_entry(), means they have covered the conditional check >>> which non_swap_entry() is doing. >> >> They are no stricter as such but implicitly contains non_swap_entry() in itself. >> If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then >> its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON. >> All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry(). >> >>> >>> Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration() >>> and is_hugetlb_entry_hwpoisoned() to simplify code. >>> >>> Signed-off-by: Baoquan He >>> Reviewed-by: Mike Kravetz >>> Reviewed-by: David Hildenbrand >>> --- >>> mm/hugetlb.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>> index 3569e731e66b..c14837854392 100644 >>> --- a/mm/hugetlb.c >>> +++ b/mm/hugetlb.c >>> @@ -3748,7 +3748,7 @@ bool is_hugetlb_entry_migration(pte_t pte) >>> if (huge_pte_none(pte) || pte_present(pte)) >>> return false; >>> swp = pte_to_swp_entry(pte); >>> - if (non_swap_entry(swp) && is_migration_entry(swp)) >>> + if (is_migration_entry(swp)) >>> return true; >>> else >>> return false; >>> @@ -3761,7 +3761,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte) >>> if (huge_pte_none(pte) || pte_present(pte)) >>> return false; >>> swp = pte_to_swp_entry(pte); >>> - if (non_swap_entry(swp) && is_hwpoison_entry(swp)) >>> + if (is_hwpoison_entry(swp)) >>> return true; >>> else >>> return false; >>> >> >> It would be better if the commit message contains details about >> the existing redundant check. But either way. > > Thanks for your advice. Do you think updating the log as below is OK? > > ~~~~~~~~ > If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then > its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON. > All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry(). > > So the checking non_swap_entry() in is_hugetlb_entry_migration() and > is_hugetlb_entry_hwpoisoned() is redundant. > > Let's remove it to optimize code. > ~~~~~~~~ Something like above would be good.