Re: [PATCH 3/3] kernel/sysctl.c: threads-max observe limits

David Rientjes
2015-02-24T22:20:09Z

On Tue, 24 Feb 2015, Heinrich Schuchardt wrote:

> >> Users can change the maximum number of threads by writing to
> >> /proc/sys/kernel/threads-max.
> >>
> >> With the patch the value entered is checked against the same
> >> limits that apply when fork_init is called.
> >>
> >
> > Correct me if I'm wrong, but this is a change in functionality (without
> > update to Documentation/sysctl/kernel.txt which describes threads-max)
> > since it does not allow the value to be lowered as before from the
> > calculation involving totalram_pages. The value passed to
> > set_max_threads() only caps the value.
>
> threads_max is set to the value the user inputs if it is inside the
> interval [20, FUTEX_TID_MASK] and it is capped by the value calculated
> from totalram_pages.
>
> So lowering and raising is still possible (inside the limits).
>

I believe this information should be added to the documentation cited
above which mentions threads-max since users will otherwise be unfamiliar
with the limits imposed.