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SubjectRe: Very aggressive swapping after 2 hours rest
On Sun, Sep 17, 2000 at 05:37:13PM -0300, Rik van Riel wrote:
> Sysrq-M displays the info for my VM too, but you'll have to
> admit that it isn't as useful as vmstat ;)

I agree about that info. That's an information not really relevant to the
internal of the memory balancing algorithm, but it's an information that
regards the state of the pagecache and that can tell how much RAM the system
really needs to perform well.

Having only a few mbytes of cache "unmapped" is an issue, having to
pagein/pageout all the time because the big cache had to be pagedin/pagedout is
a completly different thing, so I think it would be useful to export to
userspace such information as the number of pagecache pages that shouldn't be
considered "free" (in your case it's the amount of Active pages).

Just to make the opposite example in the new VM there's a field that you said
to report the net amount of allocations we get per second, averaged over one
minute, that looks more an internal "memory" of the algorithm than something
that can be useful to know to an administrator/developer. It's certainly fine
to export it via /proc/meminfo as you did so we can monitor it easily in
background and also a VM expert developer can look at with proper scripts in
case he found something strange, but I'd prefer not to make generic userspace
programs like vmstat to depend on it (tomorrow you may even choose to replace
it with some more advanced thing or just to average it in two minutes instead
of one minute or whatever else).

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