Re: [RFC][PATCH 2.5.70] Static tunable semvmx and semaem

[Manfred Spraul]

Arvind Kandhare wrote:

>
> Hi,
> Please find below patch(RFC) for implementing semvmx and semaem
> as static tunable parameters.
>
Have you thought about signed/unsigned issues? Which unix permits values 
 > 32767? Are there any potential user space problems?

I did a quick google search, and found this:
http://www.core-software.ch/samples/www/SunFire_3800/SunFire_3800.pdf, 
i.e. Solaris 2.x:
<<
SEMVMX 32767 Limits the maximum value of a semaphore. Due to the 
interaction with undo structures and semaem (see below), this tunable 
should not be increased beyond its default value of 32767, unless you 
can guarantee that SEM_UNDO is never and will never be used. It can be 
safely reduced, but doing so provides no savings.
SEMAEM 16384 Limits the maximum value of an adjust-on-exit undo element. 
No system resources are allocated based on this value.
<<

And as I wrote, I'd prefer a patch that just does s/32767/65535/ - 
either it is safe, or it's unsafe. If it's unsafe, then it should remain 
at 32767. If it safe, then we can increase it unconditionally, because a 
reduction below the upper limit provides no savings.

--
    Manfred