linux-kernel - Re: get_vmalloc_info() and /proc/meminfo insanely expensive

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Message-ID: <CA+55aFwwtN6OwEiFNLrGCS5DeffMCUy92SayfTB5cRKz3NUC-w@mail.gmail.com>
Date:	Thu, 13 Aug 2015 09:50:32 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: get_vmalloc_info() and /proc/meminfo insanely expensive

On Thu, Aug 13, 2015 at 12:42 AM, Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
>
> I think it's simpler and better to fix glibc.

Well, I certainly don't disagree, but at the same time I suspect that
(a) many distros will not update glibc very aggressively and (b) we
should fix the unnecessarily expensive kernel operation regardless.

I think that just printing out the ASCII numbers in /proc/meminfo
should be a lot more expensive than computing the numbers. Which is
clearly not the case now, because we do that crazy expensive dynamic
computation every time, even though it hardly ever really changes (and
nobody even really cares about the values).

So I'd prefer to fix the kernel for existing insane users (because the
kernel is just doing stupid things that it didn't expect anybody to
care about), _and_ fix glibc.

                     Linus
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