Date: Thu, 14 Oct 2004 01:02:25 +0200 (CEST) From: Antoine Brodin <antoine.brodin@laposte.net> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/72659: [patch] little bug in sched_ule interractivty scorer Message-ID: <200410132302.i9DN2P3S001133@massena-4-82-67-196-50.fbx.proxad.net> Resent-Message-ID: <200410132310.i9DNATW1076632@freefall.freebsd.org>
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>Number: 72659
>Category: kern
>Synopsis: [patch] little bug in sched_ule interractivty scorer
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Oct 13 23:10:28 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator: Antoine Brodin
>Release: FreeBSD 6.0-CURRENT i386
>Organization:
none
>Environment:
System: FreeBSD massena-4-82-67-196-50.fbx.proxad.net 6.0-CURRENT FreeBSD 6.0-CURRENT #0: Wed Oct 13 00:03:44 CEST 2004 antoine@massena-4-82-67-196-50.fbx.proxad.net:/usr/obj/usr/src/sys/BARTON i386
>Description:
There's a little bug in the interactivty scorer in sched_ule :
when the sleeptime is equal to the runtime, it returns 0 instead of
either SCHED_INTERACT_HALF or 0.
The routine also uses max() with signed ints, they should be replaced
by imax().
>How-To-Repeat:
You can print sleeptime, runtime and interactivity in a file and then
use gnuplot to show it in 3D.
The problem when sleeptime is equal to runtime is obvious.
Note : I can't reproduce the sleeptime is equal to runtime case easily,
durring boot I have a thread that has sleeptime=runtime=30720
but the applications I use don't seem to be "half interractive".
I can reproduce it by running during 2 or 3 minutes this ugly program
on my box (and adding a printf in the scorer code) :
#include <stdio.h>
#include <unistd.h>
int
main(void)
{
int i, j;
while (1) {
for (i = 0; i < 100000000 - j; i++)
;
usleep(250000 + j);
j += 100;
printf("%d\n", j);
}
}
>Fix:
Apply the attached patch
--- sched_ule.patch begins here ---
Index: sched_ule.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/sched_ule.c,v
retrieving revision 1.134
diff -u -r1.134 sched_ule.c
--- sched_ule.c 5 Oct 2004 22:14:02 -0000 1.134
+++ sched_ule.c 13 Oct 2004 20:09:53 -0000
@@ -1143,19 +1143,17 @@
int div;
if (kg->kg_runtime > kg->kg_slptime) {
- div = max(1, kg->kg_runtime / SCHED_INTERACT_HALF);
+ div = imax(1, kg->kg_runtime / SCHED_INTERACT_HALF);
return (SCHED_INTERACT_HALF +
(SCHED_INTERACT_HALF - (kg->kg_slptime / div)));
- } if (kg->kg_slptime > kg->kg_runtime) {
- div = max(1, kg->kg_slptime / SCHED_INTERACT_HALF);
+ }
+ if (kg->kg_slptime > kg->kg_runtime) {
+ div = imax(1, kg->kg_slptime / SCHED_INTERACT_HALF);
return (kg->kg_runtime / div);
}
-
- /*
- * This can happen if slptime and runtime are 0.
- */
+ if (kg->kg_runtime > 0)
+ return (SCHED_INTERACT_HALF);
return (0);
-
}
/*
--- sched_ule.patch ends here ---
>Release-Note:
>Audit-Trail:
>Unformatted:
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