Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752025AbdIFHzy (ORCPT ); Wed, 6 Sep 2017 03:55:54 -0400 Received: from mx2.suse.de ([195.135.220.15]:48513 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751737AbdIFHyo (ORCPT ); Wed, 6 Sep 2017 03:54:44 -0400 Subject: Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request To: js1304@gmail.com, Andrew Morton Cc: Michal Hocko , Mel Gorman , Johannes Weiner , "Aneesh Kumar K . V" , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Linux API References: <1504672525-17915-1-git-send-email-iamjoonsoo.kim@lge.com> From: Vlastimil Babka Message-ID: <86ec4ba2-44df-f8ec-70da-d389ef7a8ecc@suse.cz> Date: Wed, 6 Sep 2017 09:54:42 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <1504672525-17915-1-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4541 Lines: 120 +CC linux-api On 09/06/2017 06:35 AM, js1304@gmail.com wrote: > From: Joonsoo Kim > > Freepage on ZONE_HIGHMEM doesn't work for kernel memory so it's not that > important to reserve. When ZONE_MOVABLE is used, this problem would > theorectically cause to decrease usable memory for GFP_HIGHUSER_MOVABLE > allocation request which is mainly used for page cache and anon page > allocation. So, fix it by setting 0 to > sysctl_lowmem_reserve_ratio[ZONE_HIGHMEM]. > > And, defining sysctl_lowmem_reserve_ratio array by MAX_NR_ZONES - 1 size > makes code complex. For example, if there is highmem system, following > reserve ratio is activated for *NORMAL ZONE* which would be easyily > misleading people. > > #ifdef CONFIG_HIGHMEM > 32 > #endif > > This patch also fix this situation by defining sysctl_lowmem_reserve_ratio > array by MAX_NR_ZONES and place "#ifdef" to right place. > > Reviewed-by: Aneesh Kumar K.V > Acked-by: Vlastimil Babka > Signed-off-by: Joonsoo Kim > --- > Documentation/sysctl/vm.txt | 5 ++--- > include/linux/mmzone.h | 2 +- > mm/page_alloc.c | 25 ++++++++++++++----------- > 3 files changed, 17 insertions(+), 15 deletions(-) > > diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt > index 9baf66a..e9059d3 100644 > --- a/Documentation/sysctl/vm.txt > +++ b/Documentation/sysctl/vm.txt > @@ -336,8 +336,6 @@ The lowmem_reserve_ratio is an array. You can see them by reading this file. > % cat /proc/sys/vm/lowmem_reserve_ratio > 256 256 32 > - > -Note: # of this elements is one fewer than number of zones. Because the highest > - zone's value is not necessary for following calculation. > > But, these values are not used directly. The kernel calculates # of protection > pages for each zones from them. These are shown as array of protection pages > @@ -388,7 +386,8 @@ As above expression, they are reciprocal number of ratio. > pages of higher zones on the node. > > If you would like to protect more pages, smaller values are effective. > -The minimum value is 1 (1/1 -> 100%). > +The minimum value is 1 (1/1 -> 100%). The value less than 1 completely > +disables protection of the pages. > > ============================================================== > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 356a814..d549c4e 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -890,7 +890,7 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *, int, > void __user *, size_t *, loff_t *); > int watermark_scale_factor_sysctl_handler(struct ctl_table *, int, > void __user *, size_t *, loff_t *); > -extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1]; > +extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES]; > int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, > void __user *, size_t *, loff_t *); > int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int, > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0f34356..2a7f7e9 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -203,17 +203,18 @@ static void __free_pages_ok(struct page *page, unsigned int order); > * TBD: should special case ZONE_DMA32 machines here - in those we normally > * don't need any ZONE_NORMAL reservation > */ > -int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = { > +int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = { > #ifdef CONFIG_ZONE_DMA > - 256, > + [ZONE_DMA] = 256, > #endif > #ifdef CONFIG_ZONE_DMA32 > - 256, > + [ZONE_DMA32] = 256, > #endif > + [ZONE_NORMAL] = 32, > #ifdef CONFIG_HIGHMEM > - 32, > + [ZONE_HIGHMEM] = 0, > #endif > - 32, > + [ZONE_MOVABLE] = 0, > }; > > EXPORT_SYMBOL(totalram_pages); > @@ -6921,13 +6922,15 @@ static void setup_per_zone_lowmem_reserve(void) > struct zone *lower_zone; > > idx--; > - > - if (sysctl_lowmem_reserve_ratio[idx] < 1) > - sysctl_lowmem_reserve_ratio[idx] = 1; > - > lower_zone = pgdat->node_zones + idx; > - lower_zone->lowmem_reserve[j] = managed_pages / > - sysctl_lowmem_reserve_ratio[idx]; > + > + if (sysctl_lowmem_reserve_ratio[idx] < 1) { > + sysctl_lowmem_reserve_ratio[idx] = 0; > + lower_zone->lowmem_reserve[j] = 0; > + } else { > + lower_zone->lowmem_reserve[j] = > + managed_pages / sysctl_lowmem_reserve_ratio[idx]; > + } > managed_pages += lower_zone->managed_pages; > } > } >