From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joonsoo Kim Subject: Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request Date: Tue, 29 Aug 2017 09:36:58 +0900 Message-ID: <20170829003657.GC14489@js1304-P5Q-DELUXE> References: <1503553546-27450-1-git-send-email-iamjoonsoo.kim@lge.com> <20170825002031.GD29701@js1304-P5Q-DELUXE> <20170828002857.GB9167@js1304-P5Q-DELUXE> <78dd0160-14e8-22a6-bd10-d37bbd39f77b@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <78dd0160-14e8-22a6-bd10-d37bbd39f77b-AlSwsSmVLrQ@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Vlastimil Babka Cc: Andrew Morton , Michal Hocko , Mel Gorman , Johannes Weiner , "Aneesh Kumar K . V" , Minchan Kim , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux API List-Id: linux-api@vger.kernel.org On Mon, Aug 28, 2017 at 08:45:07AM +0200, Vlastimil Babka wrote: > +CC linux-api > > On 08/28/2017 02:28 AM, Joonsoo Kim wrote: > > On Fri, Aug 25, 2017 at 09:56:10AM +0200, Vlastimil Babka wrote: > >> On 08/25/2017 02:20 AM, Joonsoo Kim wrote: > >>> On Thu, Aug 24, 2017 at 11:41:58AM +0200, Vlastimil Babka wrote: > >>> > >>> Hmm, this is already pointed by Minchan and I have answered that. > >>> > >>> lkml.kernel.org/r/<20170421013243.GA13966@js1304-desktop> > >>> > >>> If you have a better idea, please let me know. > >> > >> My idea is that size of sysctl_lowmem_reserve_ratio is ZONE_NORMAL+1 and > >> it has no entries for zones > NORMAL. The > >> setup_per_zone_lowmem_reserve() is adjusted to only set > >> lower_zone->lowmem_reserve[j] for idx <= ZONE_NORMAL. > >> > >> I can't imagine somebody would want override the ratio for HIGHMEM or > >> MOVABLE > >> (where it has no effect anyway) so the simplest thing is not to expose > >> it at all. > > > > Seems reasonable. However, if there is a user who checks > > sysctl_lowmem_reserve_ratio entry for HIGHMEM and change it, suggested > > interface will cause a problem since it doesn't expose ratio for > > HIGHMEM. Am I missing something? > > As you explained, it makes little sense to change it for HIGHMEM which > only affects MOVABLE allocations. Also I doubt there are many systems > with both HIGHMEM (implies 32bit) *and* MOVABLE (implies NUMA, memory > hotplug...) zones. So I would just remove it, and if somebody will > really miss it, we can always add it back. In any case, please CC > linux-api on the next version. If we will accept a change that potentially breaks the user, I think that making zero as a special value for sysctl_lowmem_reserve_ratio is better solution. How about this way? Thanks.