Re: Incorrect formula for SysV IPC parameters

Thanks for looking at this.

At Fri, 12 Feb 2016 23:19:45 +0900, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote in <CAHGQGwHEnT+-S+axWKQPBYSg6z852OfgS6gDXi0Ycpq5QW=iww(at)mail(dot)gmail(dot)com>
> >> ISTM that you also need to change the descriptions about SEMMNI and SEMMNS
> >> under the Table 17-1.
> >
> > Oops! Thank you for pointing it out.
> >
> > The original description doesn't mention the magic-number ('5' in
> > the above formulas, which previously was '4') so I haven't added
> > anything about it.
> >
> > Process of which the number is limited by max_worker_processes is
> > called 'background process' (not 'backend worker') in the
> > documentation so I used the name to mention it in the additional
> > description.
> >
> > The difference in the body text for 9.2, 9.3 is only a literal
> > '4' to '5' in the formula.
>
> Thanks for updating the patches!
>
> They look good to me except that the formulas don't include the number of
> background processes requesting shared memory access, i.e.,
> GetNumShmemAttachedBgworkers(), in 9.3. Isn't it better to use the following
> formula in 9.3?
>
> ceil((max_connections + autovacuum_max_workers + number of
> background proceses + 5) / 16)
>
> Attached patch uses the above formula for 9.3. I'm thinking to push your
> patches to 9.2, 9.4, 9.5, master, also push the attached one to 9.3.
> Comments?

One concern is that users don't have any simple way to know how
many bg-workers a server runs in their current configuration.
The formula donsn't make sense without it.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center