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Re: in 3.7 kernel, how does 1GB page tables for kernel pagetables affect

To: Linda Walsh <xfs@xxxxxxxxx>
Subject: Re: in 3.7 kernel, how does 1GB page tables for kernel pagetables affect XFS?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sun, 20 Jan 2013 10:16:44 +1100
Cc: xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <50FAF860.3000702@xxxxxxxxx>
References: <50FAF860.3000702@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Sat, Jan 19, 2013 at 11:47:44AM -0800, Linda Walsh wrote:
> Given that XFS relies on the page size for it's maximum block size,
> does switching to 1GB pages for kernel pagetables allow for larger
> page-size use in XFS -- and therefore, larger blocksize?

No, it doesn't. The page cache can't use large pages so there's no
path to allowing XFS to use larger blocks with them.

As it is, you'd need a system that supports 16k or 64k page sizes
for this to be useful, otherwise you just waste a *lot* of memory...

> Is it something that might be in the not too distant future? ;-)

I have no plans to do this any time soon - there's no compelling
reason to do so. I can't speak for anyone else, though...

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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