linux-kernel - Re: [PATCH 8/8] prepare to remove /proc/sys/vm/hugepages_treat_as

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Message-ID: <87haf3oabh.fsf@linux.vnet.ibm.com>
Date:	Tue, 06 Aug 2013 07:22:02 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Hillf Danton <dhillf@...il.com>, Michal Hocko <mhocko@...e.cz>,
	Rik van Riel <riel@...hat.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH 8/8] prepare to remove /proc/sys/vm/hugepages_treat_as_movable

Naoya Horiguchi <n-horiguchi@...jp.nec.com> writes:


>> 
>> Considering that we have architectures that won't support migrating
>> explicit hugepages with this patch series, is it ok to use
>> GFP_HIGHUSER_MOVABLE for hugepage allocation ?
>
> Originally this parameter was introduced to make hugepage pool on ZONE_MOVABLE.
> The benefit is that we can extend the hugepage pool more easily,
> because external fragmentation less likely happens than other zone type
> by rearranging fragmented pages with page migration/reclaim.
>
> So I think using ZONE_MOVABLE for hugepage allocation by default makes sense
> even on the architectures which don't support hugepage migration.

But allocating hugepages from ZONE_MOVABLE means we have pages in that
zone which we can't migrate. Doesn't that impact other features like
hotplug ?


-aneesh

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