Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760356Ab3HOHpq (ORCPT ); Thu, 15 Aug 2013 03:45:46 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:63913 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756311Ab3HOHpn (ORCPT ); Thu, 15 Aug 2013 03:45:43 -0400 Message-ID: <520C8707.4000100@huawei.com> Date: Thu, 15 Aug 2013 15:45:11 +0800 From: Xishi Qiu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Minchan Kim , Mel Gorman CC: Andrew Morton , , , , LKML , Xishi Qiu Subject: Re: [PATCH] mm: skip the page buddy block instead of one page References: <520B0B75.4030708@huawei.com> <20130814085711.GK2296@suse.de> <20130814155205.GA2706@gmail.com> <20130814161642.GM2296@suse.de> <20130814163921.GC2706@gmail.com> <20130814180012.GO2296@suse.de> <520C3DD2.8010905@huawei.com> <20130815024427.GA2718@gmail.com> <520C4EFF.8040305@huawei.com> <20130815041736.GA2592@gmail.com> <20130815042434.GA3139@gmail.com> In-Reply-To: <20130815042434.GA3139@gmail.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.74.196] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2049 Lines: 85 On 2013/8/15 12:24, Minchan Kim wrote: >> Please read full thread in detail. >> >> Mel suggested following as >> >> if (PageBuddy(page)) { >> int nr_pages = (1 << page_order(page)) - 1; >> if (PageBuddy(page)) { >> nr_pages = min(nr_pages, MAX_ORDER_NR_PAGES - 1); >> low_pfn += nr_pages; >> continue; >> } >> } >> >> min(nr_pages, xxx) removes your concern but I think Mel's version >> isn't right. It should be aligned with pageblock boundary so I >> suggested following. >> >> if (PageBuddy(page)) { >> #ifdef CONFIG_MEMORY_ISOLATION >> unsigned long order = page_order(page); >> if (PageBuddy(page)) { >> low_pfn += (1 << order) - 1; >> low_pfn = min(low_pfn, end_pfn); >> } >> #endif >> continue; >> } >> Hi Minchan, I understand now, but why use "end_pfn" here? Maybe like this: if (PageBuddy(page)) { /* * page_order is racy without zone->lock but worst case * by the racing is just skipping pageblock_nr_pages. */ unsigned long nr_pages = 1 << page_order(page); if (likely(PageBuddy(page))) { nr_pages = min(nr_pages, MAX_ORDER_NR_PAGES); /* Align with pageblock boundary */ if ((low_pfn & (pageblock_nr_pages - 1)) + nr_pages > pageblock_nr_pages) low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1; else low_pfn += nr_pages - 1; } continue; } Thanks, Xishi Qiu >> so worst case is (pageblock_nr_pages - 1). >> but we don't need to add CONFIG_MEMORY_ISOLATION so my suggestion >> is following as. >> >> if (PageBuddy(page)) { >> unsigned long order = page_order(page); >> if (PageBuddy(page)) { >> low_pfn += (1 << order) - 1; >> low_pfn = min(low_pfn, end_pfn); > > Maybe it should be low_pfn = min(low_pfn, end_pfn - 1). > > >> } >> continue; >> } >> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/