[Techtalk] limits.conf, ionice, top, and befuddlements

[Wim De Smet]

Hi Carla,

On Thu, Feb 18, 2010 at 1:37 AM, Carla Schroder <carla at bratgrrl.com> wrote:
> hey all,
>
> As usual, I am dazed and confused. In /etc/security/limits.conf I have these
> entries:
>
> @audio - rtprio 99
> @audio - memlock 3000000
> @audio - nice -19
>
> My user 'alrac' is a member of the audio group. The idea is to give high
> scheduling priority for audio production. As I understand it, any process
> that alrac owns will have these priorities and memlock limit. (There are 4GB
> of RAM, so setting aside 3GB for the audio group means they are locked into
> that limit, and cannot write to swap.)

I think you have this upside down. AIUI this only governs the maximum
values that a member of the audio group can have for each of these
values. It doesn't actually set any. Worse still, if you log in as
user alrac you'll probably get the default values for nice etc., i.e.
nice value 0 which you can't lower further because you'd have to be
root to do so. The values need to be set for you by the root user (or
'login' which I think runs as root). That's my (probably flawed)
understanding anyway.

As to how to set these values easily and transparently without jumping
through too many hoops? Don't really have a clue I'm afraid.

> ionice doesn't think Audacity is special either:
>
> $ ionice -p 3236
> none: prio 0
>
> pulseaudio has its own user, pulse, which is in the audio group:
>
> $ ionice -p 3253
> none: prio 4
>
> So why does it have a priority of 4?

Is this a pulseaudio daemon? It's nice value is probably set during
startup by the init script.

regards,
Wim