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

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Message-Id: <20101013173950.0521c849.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 13 Oct 2010 17:39:50 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andi Kleen <andi@...stfloor.org>
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

On Wed, 13 Oct 2010 10:36:53 +0200
Andi Kleen <andi@...stfloor.org> wrote:

> 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?)
> 
yes. I think this patch should be update to do a precice control of memory
pressure. It will improve memory hotplug's memory allocation, too.


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

I think so, too. But maybe enough for embeded guys and very special systems
which need to use 1G page.

Thanks,
-Kame

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