linux-kernel - Re: weird DirectMap2M accounting.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Mon, 11 Jan 2016 09:58:01 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Jones <davej@...emonkey.org.uk>
cc:	Linux Kernel <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: weird DirectMap2M accounting.

On Wed, 6 Jan 2016, Dave Jones wrote:
> 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.

Agreed.

	tglx