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Date: Fri, 21 Apr 2017 10:32:46 +0900 From: Joonsoo Kim <js1304@...il.com> To: Minchan Kim <minchan@...nel.org> Cc: Andrew Morton <akpm@...ux-foundation.org>, Rik van Riel <riel@...hat.com>, Johannes Weiner <hannes@...xchg.org>, mgorman@...hsingularity.net, Laura Abbott <lauraa@...eaurora.org>, Marek Szyprowski <m.szyprowski@...sung.com>, Michal Nazarewicz <mina86@...a86.com>, "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>, Vlastimil Babka <vbabka@...e.cz>, Russell King <linux@...linux.org.uk>, Will Deacon <will.deacon@....com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel-team@....com Subject: Re: [PATCH v7 1/7] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request On Mon, Apr 17, 2017 at 04:38:08PM +0900, Minchan Kim wrote: > Hi Joonsoo, > > On Tue, Apr 11, 2017 at 12:17:14PM +0900, js1304@...il.com wrote: > > From: Joonsoo Kim <iamjoonsoo.kim@....com> > > > > 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. > > > > 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 <aneesh.kumar@...ux.vnet.ibm.com> > > Acked-by: Vlastimil Babka <vbabka@...e.cz> > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com> > > --- > > 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 ebaccd4..96194bf 100644 > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -869,7 +869,7 @@ 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 32b31d6..60ffa4e 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] = INT_MAX, > > #endif > > - 32, > > + [ZONE_MOVABLE] = INT_MAX, > > }; > > We need to update lowmem_reserve_ratio in Documentation/sysctl/vm.txt. Okay! > And to me, INT_MAX is rather awkward. I also think so. > # cat /proc/sys/vm/lowmem_reserve_ratio > 256 256 32 2147483647 2147483647 > > What do you think about to use 0 or -1 as special meaning > instead 2147483647? I have thought it but drop it. In setup_per_zone_lowmem_reserve(), there is a code to adjust the value to 1 if the value is less than 1. There might be someone who (ab)use this adjustment so it's safe to use INT_MAX. > Anyway, it could be separate patch regardless of zone_cma > so I hope Andrew to merge this patch regardless of other patches > in this patchset. Okay. I will send updated version soon. Thanks.
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