linux-kernel - Re: memory offline infinite loop after soft offline

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Message-ID: <20191018085528.GG5017@dhcp22.suse.cz>
Date:   Fri, 18 Oct 2019 10:55:28 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Qian Cai <cai@....pw>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: Re: memory offline infinite loop after soft offline

On Fri 18-10-19 10:38:21, David Hildenbrand wrote:
> On 18.10.19 10:24, Michal Hocko wrote:
> > On Fri 18-10-19 10:13:36, David Hildenbrand wrote:
> > [...]
> > > However, if the compound page spans multiple pageblocks
> > 
> > Although hugetlb pages spanning pageblocks are possible this shouldn't
> > matter in__test_page_isolated_in_pageblock because this function doesn't
> > really operate on pageblocks as the name suggests.  It is simply
> > traversing all valid RAM ranges (see walk_system_ram_range).
> 
> As long as the hugepages don't span memory blocks/sections, you are right. I
> have no experience with gigantic pages in this regard.

They can clearly span sections (1GB is larger than 128MB). Why do you
think it matters actually? walk_system_ram_range walks RAM ranges and no
allocation should span holes in RAM right?
-- 
Michal Hocko
SUSE Labs