Andrea Arcangeli <andrea@xxxxxxx> writes:
> You ignore one other bit, when "/usr/bin/free" says 1G is free, with
> config-page-shift it's free no matter what, same goes for not mlocked
> cache. With variable order page cache, /usr/bin/free becomes mostly a
> lie as long as there's no 4k fallback (like fsblock).
% free
total used free shared buffers cached
Mem: 1398784 1372956 25828 0 225224 321504
-/+ buffers/cache: 826228 572556
Swap: 1048568 20 1048548
When has free ever given any usefull "free" number? I can perfectly
fine allocate another gigabyte of memory despide free saing 25MB. But
that is because I know that the buffer/cached are not locked in.
On the other hand 1GB can instantly vanish when I start a xen domain
and anything relying on the free value would loose.
The only sensible thing for an application concerned with swapping is
to whatch the swapping and then reduce itself. Not the amount
free. Although I wish there were some kernel interface to get a
preasure value of how valuable free pages would be right now. I would
like that for fuse so a userspace filesystem can do caching without
cripling the kernel.
MfG
Goswin
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