[nycbug-talk] odd memory issue on

John Baldwin jhb at freebsd.org
Thu Oct 18 15:29:08 EDT 2012

On Thursday, October 18, 2012 2:47:42 pm Pete Wright wrote:
> On 10/18/12 11:26, Brett Wynkoop wrote:
> > Greeting-
> >
> > I just had a 32 bit system lock up on me with the need to hit the power
> > switch.  I thought it was odd because I was doing very little on it,
> > just an mv of some files from one filesystem to another.
> >
> > On rebooting I found this interesting bit of info:
> >
> > real memory  = 805306368 (768 MB)
> > avail memory = 238981120 (227 MB)
> >
> > This of course leads to:
> >
> > ZFS WARNING: Recommended minimum RAM size is 512MB; expect unstable
> > behavior. ZFS WARNING: Recommended minimum kmem_size is 512MB; expect
> > unstable behavior. Consider tuning vm.kmem_size and vm.kmem_size_max
> >               in /boot/loader.conf.
> >
> >
> > Now the $1M question......why in the world is only 227MB available?  I
> > know I have not stolen all the other memory with stupid bios settings
> > like giving it to video.
> >
> > Ideas or clues appreciated.
> you check that you don't have any failed DIMM's, or DIMM's about to fail 
> due to ECC issues?

The real memory thing can lie a bit in modern versions since it is not based
on a count of actual memory but based on what the SMBIOS tables say about
the available RAM sticks.  That said, when a DIMM fails I usually see it not 
be reported via SMBIOS either.  Can you do a verbose boot and capture the
'SMAP=' lines at the very beginning (you'll have to page up on a VGA console
or use a serial console, they are output too early to be captured in the
message buffer dumped by 'dmesg')?  Alternatively, I think there is a 'smap'
or 'show smap' command in the loader that can dump these from the loader 
prompt (and then you can take a picture).  Those lines will tell you how much 
RAM the BIOS really says is available to the OS as opposed to the sticks that 
SMBIOS says are installed.

John Baldwin

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