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Date: Wed, 26 Jul 2017 12:50:04 +0200
From: Michal Hocko <mhocko@kernel.org>
Subject: gigantic hugepages vs. movable zones
Message-ID: <20170726105004.GI2981@dhcp22.suse.cz>
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To: Luiz Capitulino <lcapitulino@redhat.com>, Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>

Hi,
I've just noticed that alloc_gigantic_page ignores movability of the
gigantic page and it uses any existing zone. Considering that
hugepage_migration_supported only supports 2MB and pgd level hugepages
then 1GB pages are not migratable and as such allocating them from a
movable zone will break the basic expectation of this zone. Standard
hugetlb allocations try to avoid that by using htlb_alloc_mask and I
believe we should do the same for gigantic pages as well.

I suspect this behavior is not intentional. What do you think about the
following untested patch?
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