linux-kernel - Re: [RFC PATCH] mm,memory_hotplug: Unlock 1GB-hugetlb on x86

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Message-ID: <20190228121115.GA10588@dhcp22.suse.cz>
Date:   Thu, 28 Feb 2019 13:11:15 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, david@...hat.com,
        mike.kravetz@...cle.com
Subject: Re: [RFC PATCH] mm,memory_hotplug: Unlock 1GB-hugetlb on x86_64

On Thu 28-02-19 11:19:52, Oscar Salvador wrote:
> On Thu, Feb 28, 2019 at 10:55:35AM +0100, Michal Hocko wrote:
> > You seemed to miss my point or I am wrong here. If scan_movable_pages
> > skips over a hugetlb page then there is nothing to migrate it and it
> > will stay in the pfn range and the range will not become idle.
> 
> I might be misunterstanding you, but I am not sure I get you.
> 
> scan_movable_pages() can either skip or not a hugetlb page.
> In case it does, pfn will be incremented to skip the whole hugetlb
> range.
> If that happens, pfn will hold the next non-hugetlb page.

And as a result the previous hugetlb page doesn't get migrated right?
What does that mean? Well, the page is still in use and we cannot
proceed with offlining because the full range is not isolated right?
-- 
Michal Hocko
SUSE Labs