Re: Why is OS X swapping with inactive memory available?
Re: Why is OS X swapping with inactive memory available?
- Subject: Re: Why is OS X swapping with inactive memory available?
- From: Terry Lambert <email@hidden>
- Date: Thu, 29 May 2008 19:07:22 -0700
On May 29, 2008, at 2:11 PM, Dan Shoop wrote:
On May 28, 2008, at 3:36 PM, Thomas Backman wrote:
Nobody?
This is very annoying... I rebooted 40 minutes ago. Since then I
started a VM with 640MB RAM (in VirtualBox, rather than VMware),
iTunes, Firefox etc. Current RAM stats:
Free: 25MB
Inactive: 1.12GB
Wired: 891MB
Active: 1007MB
Page outs: 25MB (it stopped paging when I quit Firefox)
Why is it swapping with 37% of my total RAM inactive?! I just don't
get it. Stuff starts beachballing at random, etc.
I'm starting to seriously consider switching to another OS because
of this. I can't use virtual machines anymore, and that's not the
only problem, either... Needless to say it happens without them,
too, sooner or later... :(
I realize this isn't really the "OS X support" list, just figured
people here might know what's going on.
Your presumptions about how VM [virtual memory] works on OS X are
inaccurate, which is resulting in misconceived beliefs as to what
occurring. You might consider reading Amit Singh's excellent Mac OS
X Internals book.
As for your "beachballs", these are (most generally speaking) not
caused by VM paging/swapping, but by other IO subsystem waits.
Indeed I'm not even sure VM paging could ever incur a beachball. If
you're seeing beachballs look for why your IO is stalling. "Spin
Control" can help you here.
If you're using virtual machines, this can explain, perhaps, why
you're seeing a high than normal incidence of beachballs since (a)
your IO subsystem isn't 'real', and (b) you have other virtual
machines competing for your real IO subsystem. Both of these could
contribute your your observed waits.
Again, "Spin Control", the tool, can assist you in determining what
these beachballs are caused by and could lead you to a solution.
And the "beach balls" are actually because the "are you alive?"
messages being sent to the applications run loop by the window server
(which is what controls the mouse curosor) are not responded to.
The "beach balls" are typically caused by doing blocking work in your
application run loop, instead of marshalling that work off to another
thread to get it completed there, instead. Because of that, the run
loop is not reentered at the top often enough to respond to the
events. So it's usually an indicator of an application design issue.
-- Terry
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