Semaphore scaling

[Mike Jakubik]

> -----Original Message-----
> From: Doug White [mailto:dwhite at gumbysoft.com] 
> Sent: Thursday, March 04, 2004 2:20 PM
> To: mikej at rogers.com
> Cc: stable at freebsd.org
> Subject: Re: Semaphore scaling
> 
> Don't crosspost lists. Thanks.
> 
> On Thu, 4 Mar 2004 mikej at rogers.com wrote:
> 
> > I am running an application (Plesk) on a 4.9 system that is 
> eating up 
> > all the semaphores and as a result some processes can't run. I have 
> > contacted the software company, and they asked me to increase the 
> > semaphore limits in the kernel. However their suggested settings 
> > seemed very unproportional to me.
> >
> > So my question is, how should I adjust the values, while keeping 
> > things in proportion? I wish to increase the default 
> semaphore limit 
> > of 10 to 20. Can I simply double the semaphore related values?
> 
> The semaphore tunables aren't quite as obvious as they look. 
> There are limits on the size of various clusters of things 
> whos usage is heavily application-dependent. That being said, 
> FreeBSD traditionally has very low SYSVSHM/SEM/MSG limits, so 
> doubling them should be safe.  I suggest using the ipcs(8) 
> command to monitor the usage and adjust accordingly.
> 
> The Plesk-supplied limits seem OK to me too.  I've put 
> Oracle-sized values in there and haven't had any bad effects .. yet :)
> 
> Note that you can adjust these with loader tunables as well, 
> if you don't want to rebuild the kernel.  They have the same 
> name as the sysctls that show the current values in kern.ipc.

I have adjusted the variables in /etc/sysctl.conf as follows:

kern.ipc.semmap=60
kern.ipc.semmni=20
kern.ipc.semmns=120
kern.ipc.semmnu=60
kern.ipc.semmsl=120
kern.ipc.semopm=200
kern.ipc.semume=20

However, when I do 'sysctl kern.ipc|grep sem' I get the floowing results:

kern.ipc.semmap: 60
kern.ipc.semmni: 10
kern.ipc.semmns: 60
kern.ipc.semmnu: 30
kern.ipc.semmsl: 120
kern.ipc.semopm: 100
kern.ipc.semume: 10
kern.ipc.semusz: 92
kern.ipc.semvmx: 32767
kern.ipc.semaem: 16384

It seems that kern.ipc.semmni is not being incremented. Am I doing something
wrong here? Is this variable not tunable at boot? Interesting enough, these
values in LINT are represented as x+1, i.e. SEMMAP=31 and SEMMNI=11.

Thanks.