Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751086AbcCNHGZ (ORCPT ); Mon, 14 Mar 2016 03:06:25 -0400 Received: from mx2.suse.de ([195.135.220.15]:53757 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932252AbcCNHGV (ORCPT ); Mon, 14 Mar 2016 03:06:21 -0400 Subject: Re: Suspicious error for CMA stress test To: Joonsoo Kim References: <56D92595.60709@huawei.com> <20160304063807.GA13317@js1304-P5Q-DELUXE> <56D93ABE.9070406@huawei.com> <20160307043442.GB24602@js1304-P5Q-DELUXE> <56DD38E7.3050107@huawei.com> <56DDCB86.4030709@redhat.com> <56DE30CB.7020207@huawei.com> <56DF7B28.9060108@huawei.com> <56E2FB5C.1040602@suse.cz> <20160314064925.GA27587@js1304-P5Q-DELUXE> Cc: "Leizhen (ThunderTown)" , Laura Abbott , Hanjun Guo , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Sasha Levin , Laura Abbott , qiuxishi , Catalin Marinas , Will Deacon , Arnd Bergmann , dingtinahong , chenjie6@huawei.com, "linux-mm@kvack.org" From: Vlastimil Babka Message-ID: <56E662E8.700@suse.cz> Date: Mon, 14 Mar 2016 08:06:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160314064925.GA27587@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3837 Lines: 105 On 03/14/2016 07:49 AM, Joonsoo Kim wrote: > On Fri, Mar 11, 2016 at 06:07:40PM +0100, Vlastimil Babka wrote: >> On 03/11/2016 04:00 PM, Joonsoo Kim wrote: >> >> How about something like this? Just and idea, probably buggy (off-by-one etc.). >> Should keep away cost from > relatively fewer >pageblock_order iterations. > > Hmm... I tested this and found that it's code size is a little bit > larger than mine. I'm not sure why this happens exactly but I guess it would be > related to compiler optimization. In this case, I'm in favor of my > implementation because it looks like well abstraction. It adds one > unlikely branch to the merge loop but compiler would optimize it to > check it once. I would be surprised if compiler optimized that to check it once, as order increases with each loop iteration. But maybe it's smart enough to do something like I did by hand? Guess I'll check the disassembly. > > Thanks. > >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index ff1e3cbc8956..b8005a07b2a1 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -685,21 +685,13 @@ static inline void __free_one_page(struct page *page, >> unsigned long combined_idx; >> unsigned long uninitialized_var(buddy_idx); >> struct page *buddy; >> - unsigned int max_order = MAX_ORDER; >> + unsigned int max_order = pageblock_order + 1; >> >> VM_BUG_ON(!zone_is_initialized(zone)); >> VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page); >> >> VM_BUG_ON(migratetype == -1); >> - if (is_migrate_isolate(migratetype)) { >> - /* >> - * We restrict max order of merging to prevent merge >> - * between freepages on isolate pageblock and normal >> - * pageblock. Without this, pageblock isolation >> - * could cause incorrect freepage accounting. >> - */ >> - max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1); >> - } else { >> + if (likely(!is_migrate_isolate(migratetype))) { >> __mod_zone_freepage_state(zone, 1 << order, migratetype); >> } >> >> @@ -708,11 +700,12 @@ static inline void __free_one_page(struct page *page, >> VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page); >> VM_BUG_ON_PAGE(bad_range(zone, page), page); >> >> +continue_merging: >> while (order < max_order - 1) { >> buddy_idx = __find_buddy_index(page_idx, order); >> buddy = page + (buddy_idx - page_idx); >> if (!page_is_buddy(page, buddy, order)) >> - break; >> + goto done_merging; >> /* >> * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page, >> * merge with it and move up one order. >> @@ -729,6 +722,26 @@ static inline void __free_one_page(struct page *page, >> page_idx = combined_idx; >> order++; >> } >> + if (max_order < MAX_ORDER) { >> + if (IS_ENABLED(CONFIG_CMA) && >> + unlikely(has_isolate_pageblock(zone))) { >> + >> + int buddy_mt; >> + >> + buddy_idx = __find_buddy_index(page_idx, order); >> + buddy = page + (buddy_idx - page_idx); >> + buddy_mt = get_pageblock_migratetype(buddy); >> + >> + if (migratetype != buddy_mt && >> + (is_migrate_isolate(migratetype) || >> + is_migrate_isolate(buddy_mt))) >> + goto done_merging; >> + } >> + max_order++; >> + goto continue_merging; >> + } >> + >> +done_merging: >> set_page_order(page, order); >> >> /* >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: email@kvack.org > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org >