From: Carlos Maiolino <cmaiolino@redhat.com>
To: xfs@oss.sgi.com
Subject: Re: block sizes > 4K ?? possible w/large page support?
Date: Mon, 11 Jun 2012 13:21:03 -0300 [thread overview]
Message-ID: <20120611162102.GB18432@andromeda.usersys.redhat.com> (raw)
In-Reply-To: <4FD606C1.1070103@hardwarefreak.com>
> > The maximum block size of a XFS filesystem is 64kiB. But in linux it's limited
> > to the PAGE_SIZE value.
>
> Correct.
>
> > so, on x86 architectures, the maximum block size is
> > 4kiB.
>
> Not entirely correct. Since ~1996, 16 years ago, PPro and higher 32bit
> CPUs with PSE/PSE36 support pages of 4MB, or 2MB with PAE enabled.
>
I know we can use hugepages with these sizes, but didn't know we can use this as
common usage. I tried to look at MM code and didn't find anything which would
make PAGE_SIZE greater than 4096 (at least in x86), but well, I'm not a MM
developer too.
> x86-64 CPUs in long mode also support a 2MB page size. But the problem
> of internal fragmentation may outweigh the TLB and other benefits of
> these very large pages. I'm not an MM dev so I can't elaborate further.
> There may be other issues.
>
> > although it could benefit from a 16kiB page size, you'll need to be running an
> > operating system which supports this page size value.
>
> And AFAIK the kernel MM team doesn't have x86 2MB pages on their radar.
> Or do they?
No clue, I'm not a MM developer too =/ maybe I can be someday :D
--
--Carlos
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next prev parent reply other threads:[~2012-06-11 16:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-11 3:21 block sizes > 4K ?? possible w/large page support? Linda A. Walsh
2012-06-11 13:13 ` Stan Hoeppner
2012-06-11 13:29 ` Carlos Maiolino
2012-06-11 14:54 ` Stan Hoeppner
2012-06-11 16:21 ` Carlos Maiolino [this message]
2012-06-11 21:25 ` Stefan Ring
2012-06-11 23:56 ` Dave Chinner
2012-06-12 0:08 ` Dave Chinner
2012-06-12 2:32 ` Eric Sandeen
2012-06-12 17:37 ` Linda A. Walsh
2012-06-12 18:55 ` Eric Sandeen
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