linux-kernel - Re: [RFC PATCH -mm] provide estimated available memory in /proc/meminfo

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

Message-Id: <20131105144526.49a233ca19298808e54ff900@linux-foundation.org>
Date:	Tue, 5 Nov 2013 14:45:26 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	Ron van der Wees <rvdwees@...hat.com>,
	Erik Mouw <erik.mouw_2@....com>, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, walken@...gle.com,
	Shaohua Li <shli@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [RFC PATCH -mm] provide estimated available memory in
 /proc/meminfo

On Tue, 5 Nov 2013 17:38:52 -0500 Rik van Riel <riel@...hat.com> wrote:

> Many load balancing and workload placing programs check /proc/meminfo
> to estimate how much free memory is available. They generally do this
> by adding up "free" and "cached", which was fine ten years ago, but
> is pretty much guaranteed to be wrong today.
> 
> It is wrong because Cached includes memory that is not freeable as
> page cache, for example shared memory segments, tmpfs, and ramfs,
> and it does not include reclaimable slab memory, which can take up
> a large fraction of system memory on mostly idle systems with lots
> of files.
> 
> Currently, the amount of memory that is available for a new workload,
> without pushing the system into swap, can be estimated from MemFree,
> Active(file), Inactive(file), and SReclaimable, as well as the "low"
> watermarks from /proc/zoneinfo.
> 
> However, this may change in the future, and user space really should
> not be expected to know kernel internals to come up with an estimate
> for the amount of free memory.
> 
> It is more convenient to provide such an estimate in /proc/meminfo,
> if things change in the future, we only have to change it in one
> place.
> 

That's a good idea.

>  fs/proc/meminfo.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)

Documentation/filesystems/proc.txt told me it's feeling all offended.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/