From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id B5AF16B0290 for ; Tue, 7 Nov 2017 03:30:47 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id o7so2414699pgc.23 for ; Tue, 07 Nov 2017 00:30:47 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id m15si610951pga.189.2017.11.07.00.30.46 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 07 Nov 2017 00:30:46 -0800 (PST) Date: Tue, 7 Nov 2017 09:30:42 +0100 From: Michal Hocko Subject: Re: Guaranteed allocation of huge pages (1G) using movablecore=N doesn't seem to work at all Message-ID: <20171107083042.5lnmsz237ccbituj@dhcp22.suse.cz> References: <20171106180406.diowlwanvucnwkbp@dhcp22.suse.cz> <20171106183237.64b3hj25hbfw7v4l@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Maxim Levitsky , linux-mm@kvack.org On Tue 07-11-17 09:20:47, Vlastimil Babka wrote: > On 11/06/2017 07:32 PM, Michal Hocko wrote: > > On Mon 06-11-17 20:13:36, Maxim Levitsky wrote: > >> Yes, I tested git head from mainline and few kernels from ubuntu repos > >> since I was lazy to compile them too. > > > > OK, so this hasn't worked realiably as I've suspected. > > > >> Do you have an idea what can I do about this issue? Do you think its > >> feasable to fix this? > > > > Well, I think that giga pages need quite some love to be usable > > reliably. The current implementation is more towards "make it work if > > there is enough unused memory". > > > >> And if not using moveable zone, how would it even be possible to have > >> guaranreed allocation of 1g pages > > > > Having a guaranteed giga pages is something the kernel is not yet ready > > to offer. Abusing zone movable might look like the right direction > > but that is not really the case until we make sure those pages are > > migratable. > > Migratable where? It's very unlikely you will be able to migrate them > away from a movable zone to a normal zone. So the use case is migration > between hotplugable nodes, so one of them can be removed? Yes, basically what we do for hugetlb pages normally. Smaller hugetlb pages are more likely to succeed, though. > That would > probably be an improvement (even if you could not guarantee to offline > all hotplugable nodes at once without admin intervention removing those > giga pages). Right now the only scenario where giga pages are compatible > with hot-remove is to put them on the already-limited non-removable node > 0... Yes, we will never be perfect, but I can see why people want to allocate from movable zones so we definitely should work on making giga pages more robust. The current state makes cry... -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org