linux-kernel - Re: [PATCH 0/8] v2 De-Couple sysfs memory directories from memory sections

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Date:	Wed, 29 Sep 2010 14:28:30 -0500
From:	Robin Holt <holt@....com>
To:	Nathan Fontenot <nfont@...tin.ibm.com>
Cc:	Robin Holt <holt@....com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linuxppc-dev@...abs.org,
	Greg KH <greg@...ah.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 0/8] v2 De-Couple sysfs memory directories from memory
 sections

On Tue, Sep 28, 2010 at 01:17:33PM -0500, Nathan Fontenot wrote:
> On 09/28/2010 07:38 AM, Robin Holt wrote:
> > I was tasked with looking at a slowdown in similar sized SGI machines
> > booting x86_64.  Jack Steiner had already looked into the memory_dev_init.
> > I was looking at link_mem_sections().
> > 
> > I made a dramatic improvement on a 16TB machine in that function by
> > merely caching the most recent memory section and checking to see if
> > the next memory section happens to be the subsequent in the linked list
> > of kobjects.
> > 
> > That simple cache reduced the time for link_mem_sections from 1 hour 27
> > minutes down to 46 seconds.
> 
> Nice!
> 
> > 
> > I would like to propose we implement something along those lines also,
> > but I am currently swamped.  I can probably get you a patch tomorrow
> > afternoon that applies at the end of this set.
> 
> Should this be done as a separate patch?  This patch set concentrates on
> updates to the memory code with the node updates only being done due to the
> memory changes.
> 
> I think its a good idea to do the caching and have no problem adding on to
> this patchset if no one else has any objections.

I am sorry.  I had meant to include you on the Cc: list.  I just posted a
set of patches (3 small patches) which implement the cache most recent bit
I aluded to above.  Search for a subject of "Speed up link_mem_sections
during boot" and you will find them.  I did add you to the Cc: list for
the next time I end up sending the set.

My next task is to implement a x86_64 SGI UV specific chunk of code
to memory_block_size_bytes().  Would you consider adding that to your
patch set?  I expect to have that either later today or early tomorrow.

Robin
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