Re: the Virtual Memory
Re: the Virtual Memory
- Subject: Re: the Virtual Memory
- From: Graham J Lee <email@hidden>
- Date: Fri, 09 Jun 2006 11:25:05 +0100
On 9/6/06 01:17, Jordan K. Hubbard wrote:
You might look at the source code for top(1) - it grubs through a lot of
this information.
Thanks Jordan, I actually did use top (and vm_stat) to work out how to
get the vm statistics and report on the real memory usage. At the time
I couldn't see what I wanted for swap usage, but I'll look again now
that I've read more (the virtual memory chapter in "Mach 3 Kernel
Principles" by Loepere/OSF is helping quite a lot).
To me, it looks like there's no way to produce output equivalent to the
analogous program on Linux[*], which (abridged) produces this:
total used free shared buffers cached
Swap: 2000084 0 2000084
because their VMM uses static files/partitions of fixed size and then
just works until they're full (or you swapon(2) another), whereas the
Darwin VMM is dynamically growing (and, if the moon is in the third
house and a two-headed calf has been born, plus some nonsense about low
water marks and filesizes, shrinking) its usage on the filesystem, so in
principle there's no "total" swap availability, modulo hard drive space...
...which leads me to answer a question from my original post; is there a
way to get xnu to start swapping on a new partition? The answer seems
to be to use /sbin/dynamic_pager (from system_cmds), however there's
still no way to report on what external paging files are currently in
use nor to disable one (so if you do go load-balancing your swapspace
across multiple disks, you'd better remember not to forcibly unmount any
of them). That would potentially be useful <sfx:reads some more, cracks
open Xcode>.
Cheers,
Graham.
[*]which would probably explain why I didn't do that before. :-)
--
Graham Lee
UNIX Systems Manager,
Oxford Physics Practical Course
http://iamleeg.blogspot.com/
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