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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 68D07C35247 for ; Wed, 5 Feb 2020 23:26:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42CCC2082E for ; Wed, 5 Feb 2020 23:26:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727519AbgBEX0H (ORCPT ); Wed, 5 Feb 2020 18:26:07 -0500 Received: from mga17.intel.com ([192.55.52.151]:17979 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727361AbgBEX0H (ORCPT ); Wed, 5 Feb 2020 18:26:07 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Feb 2020 15:26:06 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,407,1574150400"; d="scan'208";a="264402948" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 05 Feb 2020 15:26:03 -0800 Date: Thu, 6 Feb 2020 07:26:20 +0800 From: Wei Yang To: Baoquan He Cc: Wei Yang , David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, x86@kernel.org, Andrew Morton , Oscar Salvador , Michal Hocko , Pavel Tatashin , Dan Williams Subject: Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() Message-ID: <20200205232620.GC28446@richard> Reply-To: Wei Yang References: <20191006085646.5768-1-david@redhat.com> <20191006085646.5768-9-david@redhat.com> <20200205095924.GC24162@richard> <20200205144811.GF26758@MiWiFi-R3L-srv> <20200205225633.GA28446@richard> <20200205230826.GF8965@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205230826.GF8965@MiWiFi-R3L-srv> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 06, 2020 at 07:08:26AM +0800, Baoquan He wrote: >On 02/06/20 at 06:56am, Wei Yang wrote: >> On Wed, Feb 05, 2020 at 10:48:11PM +0800, Baoquan He wrote: >> >Hi Wei Yang, >> > >> >On 02/05/20 at 05:59pm, Wei Yang wrote: >> >> >diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> >> >index f294918f7211..8dafa1ba8d9f 100644 >> >> >--- a/mm/memory_hotplug.c >> >> >+++ b/mm/memory_hotplug.c >> >> >@@ -393,6 +393,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, >> >> > if (pfn) { >> >> > zone->zone_start_pfn = pfn; >> >> > zone->spanned_pages = zone_end_pfn - pfn; >> >> >+ } else { >> >> >+ zone->zone_start_pfn = 0; >> >> >+ zone->spanned_pages = 0; >> >> > } >> >> > } else if (zone_end_pfn == end_pfn) { >> >> > /* >> >> >@@ -405,34 +408,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, >> >> > start_pfn); >> >> > if (pfn) >> >> > zone->spanned_pages = pfn - zone_start_pfn + 1; >> >> >+ else { >> >> >+ zone->zone_start_pfn = 0; >> >> >+ zone->spanned_pages = 0; >> >> >+ } >> >> > } >> >> >> >> If it is me, I would like to take out these two similar logic out. >> > >> >I also like this style. >> >> >> >> For example: >> >> >> >> if () { >> >> } else if () { >> >> } else { >> >> goto out; >> >Here the last else is unnecessary, right? >> > >> >> I am afraid not. >> >> If the range is not the first or last, we would leave pfn not initialized. > >Ah, you are right. I forgot that one. Then pfn can be assigned the >zone_start_pfn as the old code. Then the following logic is the same >as the original code, find_smallest_section_pfn()/find_biggest_section_pfn() >have done the iteration the old for loop was doing. > > unsigned long pfn = zone_start_pfn; > if () { > } else if () { > } > > /* The zone has no valid section */ > if (!pfn) { > zone->zone_start_pfn = 0; > zone->spanned_pages = 0; > } This one look better :-) Thanks -- Wei Yang Help you, Help me