linux-kernel - Re: [RFC][PATCH 1/3] contigous big page allocator

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Message-ID: <87ocay1obe.fsf@basil.nowhere.org>
Date:	Wed, 13 Oct 2010 10:36:53 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm\@kvack.org" <linux-mm@...ck.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"minchan.kim\@gmail.com" <minchan.kim@...il.com>,
	fujita.tomonori@....ntt.co.jp
Subject: Re: [RFC][PATCH 1/3] contigous big page allocator

KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> writes:

>> >   My intention is not for allocating HUGEPAGE(> MAX_ORDER).
>> 
>> I still believe using this for 1GB pages would be one of the more
>> interesting use cases.
>> 
>
> I'm successfully allocating 1GB of continous pages at test. But I'm not sure
> requirements and users. How quick this allocation should be ?

This will always be slow. Huge pages are always pre allocated
even today through a sysctl. The use case would be have

echo XXX > /proc/sys/vm/nr_hugepages 

at runtime working for 1GB too, instead of requiring a reboot
for this. 

I think it's ok if that is somewhat slow, as long as it is not
incredible slow. Ideally it shouldn't cause a swap storm either 

(maybe we need some way to indicate how hard the freeing code should
try?)

I guess it would only really work well if you predefine
movable zones at boot time.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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