>>>>> "bf" == Bob Friesenhahn <[EMAIL PROTECTED]> writes: >>>>> "re" == Richard Elling <[EMAIL PROTECTED]> writes:
re> If you run out of space, things fail. Pinwheels are a symptom
re> of running out of RAM, not running out of swap.
okay. But what is the point?
Pinwheels are a symptom of thrashing.
Pinwheels are not showing up when the OS is returning ENOMEM.
Pinwheels are not ``things fail'', they are ``things are going slower
than some watcher thinks they should.''
AFAICT they show up when the application under the cursor has been
blocked for about five seconds, which is usually because it's
thrashing, though sometimes it's because it's trying to read from an
NFS share that went away (this also causes pinwheels).
bf> While we have seen these "pinwheels" under OS-X, the cause
bf> seems to be usually application lockup (due to poor
bf> application/library design) and not due to paging to death.
that's simply not my experience.
bf> Paging to death causes lots of obvious disk churn.
You can check for it in 'top' on OS X. they list pageins and pageouts.
bf> It is wrong to confuse total required paging space with
bf> thrashing. These are completely different issues.
and I did not. I even rephrased the word ``demand'' in terms of
thrashing. I am not confused.
bf> Dynamic sizing of paging space seems to fit well with the new
bf> zfs root/boot strategy where everything is shared via a common
bf> pool.
yes, it fits extremely well.
What I'm saying is, do not do it just because it ``fits well''. Even
if it fits really really well so it almost begs you like a sort of
compulsive taxonomical lust to put the square peg into the square
hole, don't do it, because it's a bad idea!
When applications request memory reservations that are likely to bring
the whole system down due to thrashing, they need to get ENOMEM. It
isn't okay to change the memory reservation ceiling to the ZFS pool
size, or to any other unreasonably large and not-well-considered
amount, even if the change includes a lot of mealy-mouthed pandering
orbiting around the word ``dynamic''.
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