linux-kernel - Re: [PATCH] memory hotplug disable boot option

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Date:	Fri, 25 Jun 2010 16:56:22 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Nathan Fontenot <nfont@...tin.ibm.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memory hotplug disable boot option

On Fri, Jun 25, 2010 at 09:51:37AM -0500, Nathan Fontenot wrote:
> > 
> >>> Proposed patch to disable memory hotplug via a boot option,
> >>> mem_hotplug=[on|off].  The patch only disables memory hotplug in that it 
> >>> prevents the creation of the memory sysfs directories for memory sections.
> >>>
> >>> This patch is meant to help alleviate very long boot times on systems with
> >>> large memory (1+ TB) and many memory sections (10's of thousands).
> >>
> >> Why making simple /sys file is so slowly? Couldn't we fix such performance
> >> problem?
> 
> The issue is the large number of sysfs memory directories that get created.
> On a system with 1 TB of memory I am seeing ~63,00 directories.  The long

Maybe you could simply make the memory blocks larger on such large systems?
I agree 6k blocks are probably not very useful, but maybe 10 or 100 are?

-Andi

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