Hey gang, although Intel's document seems to claim that they tested
proper operation of pause I'd like people with non-Intel processors
to verify that it actually works. Please compile the attached test
program and run it. The output should look like this:
> ./pt
Testing PAUSE instruction:
Register esp changed: 0xbfbff9fc -> 0xbfbff9c0
If you get a signal or any of the other registers change their value,
please let me know. I've tested this on a Pentium III mobile, a K6-II,
and an Athlon. The program cmopiles ok on both stable and current.
-----FW: <[EMAIL PROTECTED]>-----
Date: Tue, 21 May 2002 15:26:36 -0700 (PDT)
Sender: [EMAIL PROTECTED]
From: John Baldwin <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED], [EMAIL PROTECTED]
Subject: cvs commit: src/sys/kern kern_mutex.c
jhb 2002/05/21 15:26:36 PDT
Modified files:
sys/kern kern_mutex.c
Log:
Add appropriate IA32 "pause" instructions to improve performanec on
Pentium 4's and newer IA32 processors. The "pause" instruction has been
verified by Intel to be a NOP on all currently existing IA32 processors
prior to the Pentium 4.
Revision Changes Path
1.95 +17 -1 src/sys/kern/kern_mutex.c
--------------End of forwarded message-------------------------
--
John Baldwin <[EMAIL PROTECTED]> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
/*
* Simple program to see if the new IA32 PAUSE instruction works properly.
* We test two different things: 1) that we don't get an illegal instruction
* fault, and 2) that no registers change state.
*/
#include <sys/types.h>
#include <stdio.h>
#define NUM_SEGREGS 6
#define NUM_REGS 15
#define PUSH_REGS \
" pushf ;\n" \
" pusha ;\n" \
" push %cs ;\n" \
" push %ds ;\n" \
" push %es ;\n" \
" push %fs ;\n" \
" push %gs ;\n" \
" push %ss ;\n"
const char *register_names[NUM_REGS] = {
"ss", "gs", "fs", "es", "ds", "cs",
"edi", "esi", "ebp", "esp", "ebx", "edx", "ecx", "eax",
"eflags"
};
struct register_set {
register_t r_regs[NUM_REGS];
/*
register_t r_ss;
register_t r_gs;
register_t r_fs;
register_t r_es;
register_t r_ds;
register_t r_cs;
register_t r_edi;
register_t r_esi;
register_t r_ebp;
register_t r_isp;
register_t r_ebx;
register_t r_edx;
register_t r_ecx;
register_t r_eax;
register_t r_eflags;
*/
};
void
compare_registers(struct register_set after, struct register_set before)
{
int i;
for (i = 0; i < NUM_SEGREGS; i++) {
before.r_regs[i] &= 0xffff;
after.r_regs[i] &= 0xffff;
}
for (i = 0; i < NUM_REGS; i++)
if (before.r_regs[i] != after.r_regs[i])
printf("Register %s changed: %#x -> %#x\n",
register_names[i], before.r_regs[i],
after.r_regs[i]);
}
void
test_pause(void)
{
__asm __volatile(
" mov $10,%ecx ;\n"
PUSH_REGS
" pause ;\n"
PUSH_REGS
" call compare_registers ;\n"
" addl $0x78,%esp ;\n");
}
int
main(int ac, char **av)
{
printf("Testing PAUSE instruction:\n");
test_pause();
return (0);
}
