Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751935AbdHXJay (ORCPT ); Thu, 24 Aug 2017 05:30:54 -0400 Received: from mx2.suse.de ([195.135.220.15]:54373 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751312AbdHXJax (ORCPT ); Thu, 24 Aug 2017 05:30:53 -0400 Date: Thu, 24 Aug 2017 11:30:50 +0200 From: Michal Hocko To: js1304@gmail.com Cc: Andrew Morton , Vlastimil Babka , Mel Gorman , Johannes Weiner , "Aneesh Kumar K . V" , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim Subject: Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request Message-ID: <20170824093050.GD5943@dhcp22.suse.cz> References: <1503553546-27450-1-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1503553546-27450-1-git-send-email-iamjoonsoo.kim@lge.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3015 Lines: 85 On Thu 24-08-17 14:45:46, Joonsoo Kim 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. I do not really understand what is the problem you are trying to fix. Yes the memory is reserved for a higher priority consumer and that is deliberate AFAICT. Just consider that an OOM victim wants to make further progress and rely on memory reserve while doing GFP_HIGHUSER_MOVABLE request. So what is the real problem you are trying to address here? > 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 > --- > include/linux/mmzone.h | 2 +- > mm/page_alloc.c | 11 ++++++----- > 2 files changed, 7 insertions(+), 6 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index e7e92c8..e5f134b 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -882,7 +882,7 @@ 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 90b1996..6faa53d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -202,17 +202,18 @@ 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] = INT_MAX, > #endif > - 32, > + [ZONE_MOVABLE] = INT_MAX, > }; > > EXPORT_SYMBOL(totalram_pages); > -- > 2.7.4 > -- Michal Hocko SUSE Labs