Bad interactive behaviour in 2.5.65-66 (sched.c)

[Peter Lundkvist <p.lundkvist@telia.com>]

Hi,

I have seen long delays when starting e.g. xterm from my
window manager (sawfish) either by keyboard-shortcut or by
menu command (by mouse) starting from 2.5.65. Sometimes it
starts immediately, sometimes after up to 2 seconds (idle
system). If I start a new xterm from xterm it always start
immediately. 2.5.64 always behaved OK.

My first try to solve this problem  was to use some
scheduler parameters from 2.6.64:
    #define MAX_TIMESLICE         (300 * HZ / 1000)
    #define CHILD_PENALTY         95
    #define MAX_SLEEP_AVG         (2*HZ)
    #define STARVATION_LIMIT      (2*HZ)

but got the same behaviour.

2nd try was to use sched.c, sched.h from 2.5.64 in a
2.5.66 build + one line patch in fork.c:
-       p->last_run = jiffies;
+       p->sleep_timestamp = jiffies;

Now the system behaves as it should!

My system is a P-III 700 (Inspiron 4000),
and Debian (X is running at nice = -10).

Best regards,
Peter Lundkvist