Fwd: Tomcat6 port keeps locking up??

Jeremy Chadwick freebsd at jdc.parodius.com
Fri Sep 17 09:42:15 UTC 2010

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?

| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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