linux-kernel - Re: [PATCH 4/4] hugetlb: add hugepages

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Date:	Thu, 20 Feb 2014 10:06:03 -0500
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Marcelo Tosatti <mtosatti@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Rik van Riel <riel@...hat.com>, davidlohr@...com,
	isimatu.yasuaki@...fujitsu.com, yinghai@...nel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 4/4] hugetlb: add hugepages_node= command-line option

On Wed, 19 Feb 2014 20:51:55 -0800 (PST)
David Rientjes <rientjes@...gle.com> wrote:

> On Wed, 19 Feb 2014, Luiz Capitulino wrote:
> 
> > > Yes, my concrete objection is that the command line interface is 
> > > unnecessary if you can dynamically allocate and free 1GB pages at runtime 
> > > unless memory will be so fragmented that it cannot be done when userspace 
> > > is brought up.  That is not your use case, thus this support is not 
> > 
> > Yes it is. The early boot is the most reliable moment to allocate huge pages
> > and we want to take advantage from that.
> > 
> 
> Your use case is 8GB of hugepages on a 32GB machine.  It shouldn't be 
> necessary to do that at boot.

That's shortsighted because it's tied to a particular machine. The same
customer asked for more flexibility, too.

Look, we're also looking forward to allocating 1G huge pages from user-space.
We actually agree here. What we're suggesting is having _both_, the
command-line option (which offers higher reliability and is a low hanging
fruit right now) _and_ later we add support to allocate 1G huge pages from
user-space. No loss here, that's the maximum benefit for all users.
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