linux-kernel - Re: weird DirectMap2M accounting.

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Message-ID: <20160107001850.GA7443@codemonkey.org.uk>
Date:	Wed, 6 Jan 2016 19:18:50 -0500
From:	Dave Jones <davej@...emonkey.org.uk>
To:	Linux Kernel <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: weird DirectMap2M accounting.

On Wed, Jan 06, 2016 at 07:11:41PM -0500, Dave Jones wrote:
 > On Wed, Jan 06, 2016 at 06:55:27PM -0500, Dave Jones wrote:
 >  > I just spotted this in /proc/meminfo on an old Core2 machine with 4G.
 >  > 
 >  > DirectMap2M:    18446744073709543424 kB
 >  > 
 >  > Looks like we subtracted 8192 from 0 somewhere.
 >  > 
 >  > Should split_page_count() be checking that direct_pages_count > 0 ?
 > 
 > Ok, this diff makes that number print out as 0.
 > 
 > If this looks ok, I'll submit it properly, though I'd like to better
 > understand what's happening here. Shouldn't I have 2M pages ?

Ah. We disable them when compiling with DEBUG_PAGEALLOC.
So this is only needed in that case.
If people think it's worth an ifdef for those two added lines I'll add it,
but it seems pretty benign to just always check.

thoughts?

	Dave

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