On 17/09/2010 13:07, Jeremy Chadwick wrote:
On Fri, Sep 17, 2010 at 12:53:09PM +0300, Andriy Gapon wrote:
on 17/09/2010 12:42 Jeremy Chadwick said the following:
On Fri, Sep 17, 2010 at 12:19:00PM +0300, Andriy Gapon wrote:
on 17/09/2010 11:56 Jeremy Chadwick said the following:
I don't think you understand how Solaris's VM behaves with ZFS. It
behaves very differently than FreeBSD. On Solaris/OpenSolaris with ZFS,
you'll see the ARC taking up as much memory as possible -- but unlike
FreeBSD (AFAIK), when a userland or kernel application requires more
^^^^^^^^^^^^^^^^^
memory, the Solaris kernel dynamically releases portions of the ARC.
Can you please explain that "unlike" part?
When ZFS was first introduced to FreeBSD, I was given the impression
from continual posts on the mailing lists that memory which was
allocated to the ARC was never released in the situation that a userland
program wanted memory.
An example scenario. These numbers are in no way accurate given many
other things (network mbufs, UFS and VFS cache, etc.):
- amd64 system has 2GB physical RAM (assume ~1920MB usable)
- vm.kmem_size="1536M" + vfs.zfs.arc_max="1400M"
- Heavy ZFS I/O results in ARC maxing out at ~1400MB
- Userland application runs, requests malloc() of 1024MB
- Userland gets 384MB from physical RAM, remaining 640MB from swap
- ARC remains at 1400MB
Is this no longer the case?
I am not sure if this has even been the case :-)
It is definitely not the case now.
I trust your experience with it *much* more than mine. :-) It's very
likely that I'm basing the "ARC remains at 1400MB" claim entirely off of
what top(1) was showing under either "Inact" or "Wired".
The terminology in top(1) for memory on BSD has always confused the hell
out of me. That might sound crazy coming from someone that's been using
*IX since 1990 and BSD since 1996, but it's true. The man page does go
over what's what, but the descriptions are short one-liners (ex. "wired
down" doesn't mean anything to me). This just circles back to my lack
of knowledge about the VM.
Aren't there supposed to be 2 versions of 'top'??
Unix top and Linux top??
Both with slightly different handles on the representation of information?
I just recall reading somewhere!!
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