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From: atlas_wang AT yahoo DOT com (Wang Yong)
Newsgroups: comp.os.msdos.djgpp
Subject: Thread Swithing Time in pth1.3.7?
Date: 11 Feb 2004 19:22:25 -0800
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To: djgpp AT delorie DOT com
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Hi, 

I am testing pth1.3.7 for DJGPP, and I am curious about the
thread-switching time of it. See the following example:

#include <pth.h>
#include <stdio.h>
#include <conio.h>
#include <pc.h>

unsigned short  uPort = 0x378;
unsigned char   uchData = 0x0;

void *print_xs(void *unused)
{
    while (1) {
        uchData ^= 0x01;        /* bit0 */
        outp(uPort, uchData);
        pth_yield(NULL);
        uchData ^= 0x01;        /* bit0 */
        outp(uPort, uchData);
    }
    return NULL;
}

void *print_ys(void *unused)
{
    while (1) {
        uchData ^= 0x02;        /* bit1 */
        outp(uPort, uchData);
        pth_yield(NULL);
        uchData ^= 0x02;        /* bit1 */
        outp(uPort, uchData);
    }
    return NULL;
}

int main(void)
{
    pth_init();
    pth_spawn(NULL, print_xs, NULL);
    pth_spawn(NULL, print_ys, NULL);
    outp(uPort, uchData);

    while (1) {
        uchData ^= 0x04;        /* bit2 */
        outp(uPort, uchData);
        uchData ^= 0x04;        /* bit2 */
        outp(uPort, uchData);
        pth_yield(NULL);
    }

    pth_kill();
    return 0;
}

I use osilliscope to measure the signal from parallel port and find
that that the the time beteen rising edges is around 760 microseconds!
To be honest, it is too large to use in a time-critical environment.

The testing environment:
CPU: PII-350
CHIPSET: INTEL 440BX
MEMORY: 32M
OS: MS-DOS 6.22
COMPILER: DJGPP 2.04 alpha 1

Makefile: 
CC = gcc
CFLAGS = -O3 -Wall
PROJ = thtst
OBJS = thtst.o
LIB_OPTS = -lpth -lsocket
TARGET : $(PROJ).exe
$(PROJ1).exe : $(OBJS)
	$(CC) $(CFLAGS) -o $@ $(OBJS) $(LIB_OPTS)
	exe2coff $@
	cat -B c:\djgpp\bin\cwsdstub.exe $(PROJ) >$@
	rm -f $(PROJ)
$(OBJS) : %.o : %.c
	$(CC) $(CFLAGS) -c $<
.PHONY : clean
clean :
	rm -f *.o
	rm -f $(PROJ).exe