Some questions about vfs.zfs.prefetch_disable=1 and ZFS
filesystem versions
Jeremy Chadwick
freebsd at jdc.parodius.com
Tue Mar 16 05:11:50 UTC 2010
On Tue, Mar 16, 2010 at 01:40:25AM +0200, Dan Naumov wrote:
> After looking at the arc_summary.pl script (found at
> http://jhell.googlecode.com/files/arc_summary.pl), I have realized
> that my system has set vfs.zfs.prefetch_disable=1 by default, looking
> at dmesg, I see:
>
> =========================
> ZFS NOTICE: Prefetch is disabled by default if less than 4GB of RAM is present;
> to enable, add "vfs.zfs.prefetch_disable=0" to /boot/loader.conf.
> =========================
>
> ...except I do have 4gb of RAM. Is this caused by integrated GPU
> snatching some of my memory at boot? From dmesg:
>
> =========================
> real memory = 4294967296 (4096 MB)
> avail memory = 4088082432 (3898 MB)
> =========================
I've blogged about this problem when testing out 8.0-RC1. See the
bottom third of my post for an explanation:
http://koitsu.wordpress.com/2009/10/12/testing-out-freebsd-8-0-rc1/
The message is confusing/badly worded, despite having gone through
numerous commits to change its wording.
--
| 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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