linux-kernel - Re: Guaranteed allocation of huge pages (1G) using movablecore=N doesn't seem to work at all

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Message-ID: <20171106130507.bm75uclqqoniqwdv@dhcp22.suse.cz>
Date:   Mon, 6 Nov 2017 14:05:07 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Maxim Levitsky <maximlevitsky@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: Guaranteed allocation of huge pages (1G) using movablecore=N
 doesn't seem to work at all

On Sat 04-11-17 11:55:14, Maxim Levitsky wrote:
> Hi!
> 
> My system has 64G of ram and I want to create 32 1G huge pages to use
> in KVM virtualization,
> on demand, only when VM is running.
> 
> So I booted the kernel with
> 'hugepagesz=1G hugepages=0 default_hugepagesz=1G movablecore=40G'

Why do you think movablecore will help you? Giga pages are not
migrateable and as such they do not end up on movable zones.

I have recently changed the code to reflect that reality because
allowing giga pages to consume movable zone simply breaks memory
hotplug.
-- 
Michal Hocko
SUSE Labs