linux-kernel - Re: [PATCH 0/8] v5 De-couple sysfs memory directories from memory sections

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Date:	Wed, 1 Sep 2010 07:57:45 +1000
From:	Anton Blanchard <anton@...ba.org>
To:	Nathan Fontenot <nfont@...tin.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...abs.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Greg KH <greg@...ah.com>, akpm@...ux-foundation.org
Subject: Re: [PATCH 0/8] v5 De-couple sysfs memory directories from memory
 sections


Hi Nathan,

> This set of patches de-couples the idea that there is a single
> directory in sysfs for each memory section.  The intent of the
> patches is to reduce the number of sysfs directories created to
> resolve a boot-time performance issue.  On very large systems
> boot time are getting very long (as seen on powerpc hardware)
> due to the enormous number of sysfs directories being created.
> On a system with 1 TB of memory we create ~63,000 directories.
> For even larger systems boot times are being measured in hours.
> 
> This set of patches allows for each directory created in sysfs
> to cover more than one memory section.  The default behavior for
> sysfs directory creation is the same, in that each directory
> represents a single memory section.  A new file 'end_phys_index'
> in each directory contains the physical_id of the last memory
> section covered by the directory so that users can easily
> determine the memory section range of a directory.

I tested this on a POWER7 with 2TB memory and the boot time improved from
greater than 6 hours (I gave up), to under 5 minutes. Nice!

Tested-by: Anton Blanchard <anton@...ba.org>

Anton
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