* Re: SCHED_FIFO and SCHED_RR in 2.4.7-10custom kernel
2002-04-26 12:52 ` Nicolas Bonnefon
@ 2002-04-26 16:25 ` george anzinger
2002-04-26 20:11 ` george anzinger
1 sibling, 0 replies; 4+ messages in thread
From: george anzinger @ 2002-04-26 16:25 UTC (permalink / raw)
To: Nicolas Bonnefon
Cc: Eldor R�dseth, 'linux-kernel@vger.kernel.org'
[-- Attachment #1: Type: text/plain, Size: 2630 bytes --]
Yes, I agree that X may be in the way. It is also possible, if you are
logging in via telnet or some other remote service that the I/O service
tasks don't have the needed priority.
My solution for X is to bump its priority too.
Attached, find rt, a program to allow you to change the priority of any
task, and getrt a simple reporting program to get the priority of any
task.
By the way, if you have a relatively secure system, and you want to use
telnet, you can set the priority of inetd. This way all the I/O
services and the resulting session are boosted in priority. You must do
this ahead of time, after your task goes into a loop, its too late to
boost anything, but once you do this, you should be able to telnet into
the machine even if your task is "lost" in some loop.
-g
Nicolas Bonnefon wrote:
>
> > My application uses the possibility to change scheduling mechanism. When
> > changing from SCHED_OTHER to SCHED_FIFO or SCHED_RR, my application causes
> > the whole Linux PC to "hang". Prior to launching my own application, I
> > launch a "superbash" application with higher priority than my own
> > application. But I am not able to switch to the window where this
> > "superbash" application is running to kill my own application. The PC
> > simply does not respond to any input from the keyboard.
>
> Have you tried without running X ?
> A SCHED_FIFO or SCHED_RR task has ALWAYS priority over any SCHED_OTHER
> task, so if your application sits in an infinite loop without blocking, the
> window manager cannot preempt it and you simply cannot switch x-term.
> I think you should carefully debug your app in SCHED_OTHER mode first, and
> then switch to some real-time policy.
>
> >
> > I have used this mechanism before, and I am quite confident that this
> > worked under kernel 2.4.2. Are you aware of anything that could explain
> > this behaviour?
>
> It would be surprising, but if you were sure of that, it would deserve some
> deeper investigations !
>
> Regards
> --
> Nicolas Bonnefon
> Radar Development/Digital Processing Engineer
> Thales Air Defence - 7-9 rue des Mathurins
> 92223 Bagneux - France
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Real time sched: http://sourceforge.net/projects/rtsched/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
[-- Attachment #2: getrt.c --]
[-- Type: text/plain, Size: 1336 bytes --]
#include <sched.h>
#include <stdlib.h>
main(int args,char* argc[])
{
struct sched_param p;
pid_t pid;
int policy;
int prio,max_prio,max_rt_prio;
char * cpolicy;
if (args < 2) {
pid = 0;
}else{
pid = atoi(argc[1]);
}
policy = sched_getscheduler(pid);
sched_getparam(pid,&p);
prio = p.sched_priority;
max_prio = sched_get_priority_max(policy);
max_rt_prio = sched_get_priority_max(SCHED_FIFO);
switch(policy){
case SCHED_OTHER:
cpolicy = "SCHED_OTHER";
break;
case SCHED_RR:
cpolicy = "SCHED_RR";
break;
case SCHED_FIFO:
cpolicy = "SCHED_FIFO";
break;
default:
perror("sched_getscheduler");
exit(1);
}
if (policy == SCHED_OTHER){
printf("%s at priority %d (MAX_PRIO(%s) = %d, MAX_PRIO(SCHED_FIFO) = %d)\n",
cpolicy, prio, cpolicy,max_prio, max_rt_prio);
}else{
printf("%s at priority %d (MAX_PRIO(%s) = %d)\n",
cpolicy, prio, cpolicy, max_prio);
}
exit(0);
}
[-- Attachment #3: rt.c --]
[-- Type: text/plain, Size: 3205 bytes --]
/*
rt - a utility to set the realtime priority and scheduling policy
*/
/* includes */
#include <stdio.h>
#include <stdlib.h>
#include <sched.h>
#include <unistd.h>
#define _GNU_LIBRARY__
#include <getopt.h>
/* defines */
#define RUNSTRING "usage: rt [-f] [-v] prio [--] runstring \n \
or: rt [-f] [-v] -p PID prio\\ \n\n \
where: prio specifies the realtime priority \n \
-f set scheduling policy to SCHED_FIFO \n \
-v turns on verbose mode. \n \
-p PID specifies an existing process to modify \n \
runstring is a process and parameters \n \
(use '--' if runstring contains options). \n"
#define POLICY(x) x ? x-1 ? "SCHED_RR" : "SCHED_FIFO" : "SCHED_OTHER"
/* prototypes */
void print_usage(char *[]);
/* globals */
int verbose=0; /* 0=none, !0=verbose */
main(int argc, char *argv[])
{
struct sched_param prio_struct;
int policy = -1;
int pid = 0;
int pidopt = 0;
int optprobs = 0; /* problems parsing? */
int c; /* generic single character */
/* "standard" option parsing... */
while ( (c=getopt(argc, argv, "+fp:v?")) != EOF)
{
switch (c) {
case 'f': /* set FIFO mode */
policy = SCHED_FIFO;
break;
case 'p': /* read PID */
sscanf(optarg,"%d",&pid);
pidopt=1;
break;
case 'v':
verbose=1; /* verbosity */
break;
case '?': /* help? */
printf("%s",RUNSTRING);
exit(0);
default: /* something went wrong */
optprobs=1; /* we'll deal with this problem later */
break;
}
}
if (optprobs) {
fprintf(stderr,RUNSTRING);
exit(1);
}
if((argc - optind) < 2-pidopt) {
print_usage(argv);
}
sscanf(argv[optind], "%d", &(prio_struct.sched_priority));
/* sanity checking... */
if ( (prio_struct.sched_priority != 0) && (policy < 0 ) ) {
policy=SCHED_RR;
if (verbose)
printf("Defaulting sched policy to %s.\n", POLICY(policy));
}
if ( (prio_struct.sched_priority == 0 ) && (policy != SCHED_OTHER) ) {
policy=SCHED_OTHER;
fprintf(stderr,"Priority of %d implies sched policy of %s.\n",
prio_struct.sched_priority, POLICY(policy));
}
policy = (prio_struct.sched_priority)? policy : SCHED_OTHER;
if( sched_setscheduler(pid,policy,&prio_struct)){
perror("Priority out of range");
print_usage(argv);
}
if ( pid ) exit(0);
argv+=optind; /* adjust argv to point to the runstring */
argv++;
execvp(argv[0],argv);
perror("exec failed..");
}
void print_usage(char * who[])
{
printf("%s",RUNSTRING);
exit (1);
}
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: SCHED_FIFO and SCHED_RR in 2.4.7-10custom kernel
2002-04-26 12:52 ` Nicolas Bonnefon
2002-04-26 16:25 ` george anzinger
@ 2002-04-26 20:11 ` george anzinger
1 sibling, 0 replies; 4+ messages in thread
From: george anzinger @ 2002-04-26 20:11 UTC (permalink / raw)
To: 'linux-kernel@vger.kernel.org'
[-- Attachment #1: Type: text/plain, Size: 2630 bytes --]
Yes, I agree that X may be in the way. It is also possible, if you are
logging in via telnet or some other remote service that the I/O service
tasks don't have the needed priority.
My solution for X is to bump its priority too.
Attached, find rt, a program to allow you to change the priority of any
task, and getrt a simple reporting program to get the priority of any
task.
By the way, if you have a relatively secure system, and you want to use
telnet, you can set the priority of inetd. This way all the I/O
services and the resulting session are boosted in priority. You must do
this ahead of time, after your task goes into a loop, its too late to
boost anything, but once you do this, you should be able to telnet into
the machine even if your task is "lost" in some loop.
-g
Nicolas Bonnefon wrote:
>
> > My application uses the possibility to change scheduling mechanism. When
> > changing from SCHED_OTHER to SCHED_FIFO or SCHED_RR, my application causes
> > the whole Linux PC to "hang". Prior to launching my own application, I
> > launch a "superbash" application with higher priority than my own
> > application. But I am not able to switch to the window where this
> > "superbash" application is running to kill my own application. The PC
> > simply does not respond to any input from the keyboard.
>
> Have you tried without running X ?
> A SCHED_FIFO or SCHED_RR task has ALWAYS priority over any SCHED_OTHER
> task, so if your application sits in an infinite loop without blocking, the
> window manager cannot preempt it and you simply cannot switch x-term.
> I think you should carefully debug your app in SCHED_OTHER mode first, and
> then switch to some real-time policy.
>
> >
> > I have used this mechanism before, and I am quite confident that this
> > worked under kernel 2.4.2. Are you aware of anything that could explain
> > this behaviour?
>
> It would be surprising, but if you were sure of that, it would deserve some
> deeper investigations !
>
> Regards
> --
> Nicolas Bonnefon
> Radar Development/Digital Processing Engineer
> Thales Air Defence - 7-9 rue des Mathurins
> 92223 Bagneux - France
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Real time sched: http://sourceforge.net/projects/rtsched/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
[-- Attachment #2: getrt.c --]
[-- Type: text/plain, Size: 1337 bytes --]
#include <sched.h>
#include <stdlib.h>
main(int args,char* argc[])
{
struct sched_param p;
pid_t pid;
int policy;
int prio,max_prio,max_rt_prio;
char * cpolicy;
if (args < 2) {
pid = 0;
}else{
pid = atoi(argc[1]);
}
policy = sched_getscheduler(pid);
sched_getparam(pid,&p);
prio = p.sched_priority;
max_prio = sched_get_priority_max(policy);
max_rt_prio = sched_get_priority_max(SCHED_FIFO);
switch(policy){
case SCHED_OTHER:
cpolicy = "SCHED_OTHER";
break;
case SCHED_RR:
cpolicy = "SCHED_RR";
break;
case SCHED_FIFO:
cpolicy = "SCHED_FIFO";
break;
default:
perror("sched_getscheduler");
exit(1);
}
if (policy == SCHED_OTHER){
printf("%s at priority %d (MAX_PRIO(%s) = %d, MAX_PRIO(SCHED_FIFO) = %d)\n",
cpolicy, prio, cpolicy,max_prio, max_rt_prio);
}else{
printf("%s at priority %d (MAX_PRIO(%s) = %d)\n",
cpolicy, prio, cpolicy, max_prio);
}
exit(0);
}
[-- Attachment #3: rt.c --]
[-- Type: text/plain, Size: 3206 bytes --]
/*
rt - a utility to set the realtime priority and scheduling policy
*/
/* includes */
#include <stdio.h>
#include <stdlib.h>
#include <sched.h>
#include <unistd.h>
#define _GNU_LIBRARY__
#include <getopt.h>
/* defines */
#define RUNSTRING "usage: rt [-f] [-v] prio [--] runstring \n \
or: rt [-f] [-v] -p PID prio\\ \n\n \
where: prio specifies the realtime priority \n \
-f set scheduling policy to SCHED_FIFO \n \
-v turns on verbose mode. \n \
-p PID specifies an existing process to modify \n \
runstring is a process and parameters \n \
(use '--' if runstring contains options). \n"
#define POLICY(x) x ? x-1 ? "SCHED_RR" : "SCHED_FIFO" : "SCHED_OTHER"
/* prototypes */
void print_usage(char *[]);
/* globals */
int verbose=0; /* 0=none, !0=verbose */
main(int argc, char *argv[])
{
struct sched_param prio_struct;
int policy = -1;
int pid = 0;
int pidopt = 0;
int optprobs = 0; /* problems parsing? */
int c; /* generic single character */
/* "standard" option parsing... */
while ( (c=getopt(argc, argv, "+fp:v?")) != EOF)
{
switch (c) {
case 'f': /* set FIFO mode */
policy = SCHED_FIFO;
break;
case 'p': /* read PID */
sscanf(optarg,"%d",&pid);
pidopt=1;
break;
case 'v':
verbose=1; /* verbosity */
break;
case '?': /* help? */
printf("%s",RUNSTRING);
exit(0);
default: /* something went wrong */
optprobs=1; /* we'll deal with this problem later */
break;
}
}
if (optprobs) {
fprintf(stderr,RUNSTRING);
exit(1);
}
if((argc - optind) < 2-pidopt) {
print_usage(argv);
}
sscanf(argv[optind], "%d", &(prio_struct.sched_priority));
/* sanity checking... */
if ( (prio_struct.sched_priority != 0) && (policy < 0 ) ) {
policy=SCHED_RR;
if (verbose)
printf("Defaulting sched policy to %s.\n", POLICY(policy));
}
if ( (prio_struct.sched_priority == 0 ) && (policy != SCHED_OTHER) ) {
policy=SCHED_OTHER;
fprintf(stderr,"Priority of %d implies sched policy of %s.\n",
prio_struct.sched_priority, POLICY(policy));
}
policy = (prio_struct.sched_priority)? policy : SCHED_OTHER;
if( sched_setscheduler(pid,policy,&prio_struct)){
perror("Priority out of range");
print_usage(argv);
}
if ( pid ) exit(0);
argv+=optind; /* adjust argv to point to the runstring */
argv++;
execvp(argv[0],argv);
perror("exec failed..");
}
void print_usage(char * who[])
{
printf("%s",RUNSTRING);
exit (1);
}
^ permalink raw reply [flat|nested] 4+ messages in thread