Subject: [linux-audio-dev] [CODE RFC] redefining sched_setscheduler using LD_PRELOAD
From: Roger Larsson (roger.larsson_AT_norran.net)
Date: Fri Nov 14 2003 - 07:15:06 EET
Hi,
(Jack O'Quin got me thinking about rt_monitor again - thanks!)
This is an alternative to capabilities / SCHED_SOFTRR...
I use my old rt_monitor
* protects the system on RT overload
* performs the actual setting of scheduler type
* it does not even have to be visible for lusers!
My old testprogram RT has been converted to
a library fit for preloading.
It works like this.
As root start
# rt_monitor
As normal user start latencytest
$ ./rts path/to/latencytest none 2 128 10
rts has two options
-i do not raise the priority.
-v be more verbose.
* It does also limit the effective min/max range.
Do also try (don't try this as root unless rt_monitor is running)
$ ./rts path/to/latencytest none 2 1024 99
* In this case rt_monitor captures the process and renices it.
(SCHED_OTHER + nice)
BUGS:
* better build and installation system
* could ignore RT processes already running when rt_monitor starts
* rt_monitor functionallity has not been reverified...
* it can't lock memory :-( No PIDs in calls.
* code that checks uid before using the redefined functions won't work
(I have an modified latencytest)
* client get stuck if there is no monitor running.
/RogerL
-- Roger Larsson Skellefteċ Sweden
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