Messages in this thread |  | | Date | Tue, 5 Nov 2013 14:45:26 -0800 | From | Andrew Morton <> | Subject | Re: [RFC PATCH -mm] provide estimated available memory in /proc/meminfo |
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On Tue, 5 Nov 2013 17:38:52 -0500 Rik van Riel <riel@redhat.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.
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