Re: FreeBSD 7 needing to allocate lots of shared memory

Hello Shane,

All settings are as expected by both sysctl.conf and loader.conf

Shane Ambler wrote:
> Christiaan Willemsen wrote:
>> Bill Moran wrote:
>>> In response to Christiaan Willemsen <cwillemsen(at)technocon(dot)com>:
>>>
>>>
>>>> #sysctl -a | grep shm
>>>> kern.ipc.shm_allow_removed: 0
>>>> kern.ipc.shm_use_phys: 1
>>>> kern.ipc.shmall: 68719476736
>>>> kern.ipc.shmseg: 128
>>>> kern.ipc.shmmni: 192
>>>> kern.ipc.shmmin: 1
>>>> kern.ipc.shmmax: 68719476736
>>>>
>>>
>>> Try bumping shmmni:
>>> $ sysctl -d kern.ipc.shmmni
>>> kern.ipc.shmmni: Number of shared memory identifiers
>>>
>>> I have this set to 1000 on most of my systems. Can't seem to find my
>>> notes on it right now, but that may be your holdup. The PG docs seem
>>> to indicate that this number can be set very low, as PG only needs a
>>> single identifier, but I must have had _some_ reason for raising it.
>>>
> > Hello Bill,
> >
> > I have this one set to 512 in loader.conf
> > other params in loader.conf:
>
> Your sysctl output above shows kern.ipc.shmmni is set to 192
>
> > kern.ipc.semmni=1024
> > kern.ipc.semmns=1024
> > kern.ipc.semmnu=512
>
> Take a close look here.
>
> Christiaan mentioned kern.ipc.shmmni the list above shows
> kern.ipc.semmni (you may only be listing others)
>
> Double check that your settings are what you expect.
>
> Also check /etc/sysctl.conf which may override some of the changeable
> options from loader.conf.
>
> Settings in loader.conf are only required for read-only options (that
> need a reboot to take effect). Others are often changed in sysctl.conf
>
> Check your running settings against what you expect.
>
>
>
> Just a guess here - kern.ipc.shmall and kern.ipc.shmmax seem very high
> but not sure if this can lead to the issue.
>
> > sysctl -d kern.ipc.shmmax
> kern.ipc.shmmax: Maximum shared memory segment size
>
> > sysctl -d kern.ipc.shmall
> kern.ipc.shmall: Maximum number of pages available for shared memory
>
> Looks like you have set this to equal your installed RAM but a page is
> a bit more than one byte. (is it 4K to a page?)
>
>
>
> You haven't mentioned whether you are using the generic kernel or a
> custom built one (with what changes?)
>
>
> For reference - I have an old P4 3Ghz with 1GB RAM (32bit)
> FreeBSD 7 release with a custom kernel to turn on the new scheduler
>
> I can set shared_buffers to 64MB (you mentioned trouble over 32MB)
>
> fbsd# sysctl -a | grep shm
> kern.ipc.shm_allow_removed: 0
> kern.ipc.shm_use_phys: 1
> kern.ipc.shmall: 32768
> kern.ipc.shmseg: 128
> kern.ipc.shmmni: 192
> kern.ipc.shmmin: 1
> kern.ipc.shmmax: 134217728
>
> fbsd# sysctl -a | grep sem
> kern.ipc.semaem: 16384
> kern.ipc.semvmx: 32767
> kern.ipc.semusz: 92
> kern.ipc.semume: 10
> kern.ipc.semopm: 100
> kern.ipc.semmsl: 60
> kern.ipc.semmnu: 30
> kern.ipc.semmns: 60
> kern.ipc.semmni: 10
> kern.ipc.semmap: 256
>