linux-kernel - Re: [PATCH 3/3 v3] mm/vmalloc: Cache the vmalloc memory info

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Date:	Mon, 24 Aug 2015 09:00:01 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	George Spelvin <linux@...izon.com>, dave@...1.net,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	peterz@...radead.org, riel@...hat.com, rientjes@...gle.com,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH 3/3 v3] mm/vmalloc: Cache the vmalloc memory info


* Rasmus Villemoes <linux@...musvillemoes.dk> wrote:

> I was curious why these fields were ever added to /proc/meminfo, and dug
> up this:
> 
> commit d262ee3ee6ba4f5f6125571d93d9d63191d2ef76
> Author: Andrew Morton <akpm@...eo.com>
> Date:   Sat Apr 12 12:59:04 2003 -0700
> 
>     [PATCH] vmalloc stats in /proc/meminfo
>     
>     From: Matt Porter <porter@....net>
>     
>     There was a thread a while back on lkml where Dave Hansen proposed this
>     simple vmalloc usage reporting patch.  The thread pretty much died out as
>     most people seemed focused on what VM loading type bugs it could solve.  I
>     had posted that this type of information was really valuable in debugging
>     embedded Linux board ports.  A common example is where people do arch
>     specific setup that limits there vmalloc space and then they find modules
>     won't load.  ;) Having the Vmalloc* info readily available is real useful in
>     helping folks to fix their kernel ports.
> 
> That thread is at <http://thread.gmane.org/gmane.linux.kernel/53360>.
> 
> [Maybe one could just remove the fields and see if anybody actually
> notices/cares any longer. Or, if they are only used by kernel
> developers, put them in their own file.]

So instead of removing the fields (which I'm quite sure is an ABI breaker as it 
could break less robust /proc/meminfo parsers and scripts), we could just report 
'0' all the time - and have the real info somewhere else?

Thanks,

	Ingo
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