block sizes > 4K ?? possible w/large page support?

[Stan Hoeppner]

On 6/11/2012 8:29 AM, Carlos Maiolino wrote:

> 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.

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?

-- 
Stan