linux-kernel - Re: [PATCH 1/2] Report the pagesize backing a VMA in /proc/pid/smaps

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Message-ID: <20080923194655.GA25542@csn.ul.ie>
Date:	Tue, 23 Sep 2008 20:46:56 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 1/2] Report the pagesize backing a VMA in /proc/pid/smaps

On (23/09/08 21:15), KOSAKI Motohiro didst pronounce:
> > > The corollary is that someone running with a 64K base page kernel may be
> > > surprised that the pagesize is always 4K. However I'll check if there is
> > > a simple way of checking out if the MMU size differs from PAGE_SIZE.
> > 
> > Sure.  If it isn't easy, the best thing to do is probably just to
> > document the "interesting" behavior.
> 
> Dave, please let me know getpagesize() function return to 4k or 64k on ppc64.
> I think the PageSize line of the /proc/pid/smap and getpagesize() result should be matched.
> 
> otherwise, enduser may be confused.
> 

To distinguish between the two, I now report the kernel pagesize and the
mmu pagesize like so

KernelPageSize:       64 kB
MMUPageSize:           4 kB

This is running a kernel with a 64K base pagesize on a PPC970MP which
does not support 64K hardware pagesizes.

Does this make sense?

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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