Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761174AbaGRJbR (ORCPT ); Fri, 18 Jul 2014 05:31:17 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:39536 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1760840AbaGRJbQ convert rfc822-to-8bit (ORCPT ); Fri, 18 Jul 2014 05:31:16 -0400 X-IronPort-AV: E=Sophos;i="5.00,914,1396972800"; d="scan'208";a="33452252" Message-ID: <53C8E92F.1010805@cn.fujitsu.com> Date: Fri, 18 Jul 2014 17:30:23 +0800 From: Zhang Yanfei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131030 Thunderbird/17.0.10 MIME-Version: 1.0 To: Gioh Kim CC: Marek Szyprowski , Andrew Morton , =?UTF-8?B?J+q5gOykgOyImCc=?= , Laura Abbott , Minchan Kim , Michal Nazarewicz , Alexander Viro , Johannes Weiner , Mel Gorman , , , =?UTF-8?B?7J206rG07Zi4?= , "'Chanho Min'" Subject: Re: [PATCH] CMA/HOTPLUG: clear buffer-head lru before page migration References: <53C8C290.90503@lge.com> <53C8D1CA.9070102@samsung.com> <53C8D970.4000908@lge.com> In-Reply-To: <53C8D970.4000908@lge.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Originating-IP: [10.167.225.89] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 07/18/2014 04:23 PM, Gioh Kim wrote: > > > 2014-07-18 오후 4:50, Marek Szyprowski 쓴 글: >> Hello, >> >> On 2014-07-18 08:45, Gioh Kim wrote: >>> For page migration of CMA, buffer-heads of lru should be dropped. >>> Please refer to https://lkml.org/lkml/2014/7/4/101 for the history. >>> >>> I have two solution to drop bhs. >>> One is invalidating entire lru. >>> Another is searching the lru and dropping only one bh that Laura proposed >>> at https://lkml.org/lkml/2012/8/31/313. >>> >>> I'm not sure which has better performance. >>> So I did performance test on my cortex-a7 platform with Lmbench >>> that has "File & VM system latencies" test. >>> I am attaching the results. >>> The first line is of invalidating entire lru and the second is dropping selected bh. >>> >>> File & VM system latencies in microseconds - smaller is better >>> ------------------------------------------------------------------------------- >>> Host OS 0K File 10K File Mmap Prot Page 100fd >>> Create Delete Create Delete Latency Fault Fault selct >>> --------- ------------- ------ ------ ------ ------ ------- ----- ------- ----- >>> 10.178.33 Linux 3.10.19 25.1 19.6 32.6 19.7 5098.0 0.666 3.45880 6.506 >>> 10.178.33 Linux 3.10.19 24.9 19.5 32.3 19.4 5059.0 0.563 3.46380 6.521 >>> >>> >>> I tried several times but the result tells that they are the same under 1% gap >>> except Protection Fault. >>> But the latency of Protection Fault is very small and I think it has little effect. >>> >>> Therefore we can choose anything but I choose invalidating entire lru. >>> The try_to_free_buffers() which is calling drop_buffers() is called by many filesystem code. >>> So I think inserting codes in drop_buffers() can affect the system. >>> And also we cannot distinguish migration type in drop_buffers(). >>> >>> In alloc_contig_range() we can distinguish migration type and invalidate lru if it needs. >>> I think alloc_contig_range() is proper to deal with bh like following patch. >>> >>> Laura, can I have you name on Acked-by line? >>> Please let me represent my thanks. >>> >>> Thanks for any feedback. >>> >>> ------------------------------- 8< ---------------------------------- >>> >>> >From 33c894b1bab9bc26486716f0c62c452d3a04d35d Mon Sep 17 00:00:00 2001 >>> From: Gioh Kim >>> Date: Fri, 18 Jul 2014 13:40:01 +0900 >>> Subject: [PATCH] CMA/HOTPLUG: clear buffer-head lru before page migration >>> >>> The bh must be free to migrate a page at which bh is mapped. >>> The reference count of bh is increased when it is installed >>> into lru so that the bh of lru must be freed before migrating the page. >>> >>> This frees every bh of lru. We could free only bh of migrating page. >>> But searching lru costs more than invalidating entire lru. >>> >>> Signed-off-by: Gioh Kim >>> Acked-by: Laura Abbott >>> --- >>> mm/page_alloc.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index b99643d4..3b474e0 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -6369,6 +6369,9 @@ int alloc_contig_range(unsigned long start, unsigned long end, >>> if (ret) >>> return ret; >>> >>> + if (migratetype == MIGRATE_CMA || migratetype == MIGRATE_MOVABLE) >> >> I'm not sure if it really makes sense to check the migratetype here. This check >> doesn't add any new information to the code and make false impression that this >> function can be called for other migratetypes than CMA or MOVABLE. Even if so, >> then invalidating bh_lrus unconditionally will make more sense, IMHO. > > I agree. I cannot understand why alloc_contig_range has an argument of migratetype. > Can the alloc_contig_range is called for other migrate type than CMA/MOVABLE? > > What do you think about removing the argument of migratetype and > checking migratetype (if (migratetype == MIGRATE_CMA || migratetype == MIGRATE_MOVABLE))? > Remove the checking only. Because gigantic page allocation used for hugetlb is using alloc_contig_range(...... MIGRATE_MOVABLE). Thanks. -- Thanks. Zhang Yanfei -- 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/