On Dec 12, 2007 7:31 AM, Rene Herman <[email protected]> wrote:
> Good day.
>
> Would some people on x86 (both 32 and 64) be kind enough to compile and run
> the attached program? This is about testing how long I/O port access to port
> 0x80 takes. It measures in CPU cycles so CPU speed is crucial in reporting.
>
> Posted a previous incarnation of this before, buried in the outb 0x80 thread
> which had a serialising problem. This one should as far as I can see measure
> the right thing though. Please yell if you disagree...
>
> For me, on a Duron 1300 (AMD756 chipset) I have a constant:
>
> rene@7ixe4:~/src/port80$ su -c ./port80
> cycles: out 2400, in 2400
>
> and on a PII 400 (Intel 440BX chipset) a constant:
>
> rene@6bap:~/src/port80$ su -c ./port80
> cycles: out 553, in 251
>
> Results are (mostly) independent of compiler optimisation, but testing with
> an -O2 compile should be most useful. Thanks!
>
> Rene.
>
> /* gcc -W -Wall -O2 -o port80 port80.c */
>
> #include <stdlib.h>
> #include <stdio.h>
>
> #include <sys/io.h>
>
> #define LOOPS 10000
>
> inline unsigned long long rdtsc(void)
> {
> unsigned long long tsc;
>
> asm volatile ("rdtsc": "=A" (tsc));
>
> return tsc;
> }
>
> inline void serialize(void)
> {
> asm volatile ("cpuid": : : "eax", "ebx", "ecx", "edx");
> }
>
> int main(void)
> {
> unsigned long long start;
> unsigned long long overhead;
> unsigned long long output;
> unsigned long long input;
> int i;
>
> if (iopl(3) < 0) {
> perror("iopl");
> return EXIT_FAILURE;
> }
>
> asm volatile ("cli");
> start = rdtsc();
> for (i = 0; i < LOOPS; i++) {
> serialize();
> serialize();
> }
> overhead = rdtsc() - start;
>
> start = rdtsc() + overhead;
> for (i = 0; i < LOOPS; i++) {
> serialize();
> asm volatile ("outb %al, $0x80");
> serialize();
> }
> output = rdtsc() - start;
>
> start = rdtsc() + overhead;
> for (i = 0; i < LOOPS; i++) {
> serialize();
> asm volatile ("inb $0x80, %%al": : : "al");
> serialize();
> }
> input = rdtsc() - start;
> asm volatile ("sti");
>
> output /= LOOPS;
> input /= LOOPS;
> printf("cycles: out %llu, in %llu\n", output, input);
>
> return EXIT_SUCCESS;
> }
>
>
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2522, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2522, in 1795
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2523, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2516, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2516, in 1798
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2523, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2518, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2517, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2523, in 1788
dave@darkstar:~/work/tmp$ sudo ./port80
cycles: out 2517, in 1788
dave@darkstar:~$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Pentium(R) D CPU 2.80GHz
stepping : 7
cpu MHz : 2793.194
cache size : 1024 KB
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