Did you try to insert a usleep(1) before the writev() syscall? This
_might_ narrow down the noise as the last timer interrupt is just done when
usleep returns (On i386, the time resolution is 1/100s = 10000usec;
AFAIK usleep will not sleep shorter than time resolution.)
wwieser
On Tuesday 22 May 2001 00:28, Pavel Kankovsky wrote:
> <--snip-->
>
> cookie.c (X11 test):
> <--snip-->
> #include <stdio.h>
> #include <string.h>
> #include <sys/uio.h>
> #include <sys/socket.h>
> #include <sys/un.h>
>
> /* taken from Linux kernel */
> #define rdtsc(low, high) \
> __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
> #define sub64(xlow, xhigh, ylow, yhigh) \
> __asm__("subl %2,%0\n\tsbbl %3,%1" \
>
> :"=a" (xlow), "=d" (xhigh) \
> :"g" (ylow), "g" (yhigh), \
>
> "0" (xlow), "1" (xhigh))
> unsigned long
> measure(int dpy, const char *cookie)
> {
> unsigned long startlo, starthi;
> unsigned long endlo, endhi;
> int s, r;
> char c;
> struct iovec vec[4];
> struct sockaddr_un sun;
>
> vec[0].iov_base = "l\0\v\0\0\0\22\0\20\0\0\0";
> vec[0].iov_len = 12;
> vec[1].iov_base = "MIT-MAGIC-COOKIE-1";
> vec[1].iov_len = 18;
> vec[2].iov_base = "\0\0";
> vec[2].iov_len = 2;
> vec[3].iov_base = (char *) cookie;
> vec[3].iov_len = 16;
>
> s = socket(AF_UNIX, SOCK_STREAM, 0);
> if (s < 0) return ~0UL;
> sun.sun_family = AF_UNIX;
> sprintf(sun.sun_path, "/tmp/.X11-unix/X%d", dpy);
> r = connect(s, (struct sockaddr *) &sun, sizeof(sun));
> if (r < 0) { close(s); return ~0UL; }
usleep(1);
> rdtsc(startlo, starthi);
> (void) writev(s, vec, 4);
> (void) read(s, &c, 1);
> rdtsc(endlo, endhi);
> sub64(endlo, endhi, startlo, starthi);
>
> close(s);
> if (endhi) return ~0UL; /* argh */
> return endlo;
> }
>
> int
> main()
> {
> char a[16], b[16];
> int i, j, count;
> unsigned long ta, tb, tmin, t1;
>
> for (j = 0; j < sizeof(a); ++j)
> a[j] = j;
> for (i = 0; i <= sizeof(a); ++i) {
> for (j = 0; j < i; ++j) b[j] = a[j];
> for (; j < sizeof(a); ++j) b[j] = ~a[j];
> count = 100000;
> ta = tb = 0; tmin = ~0UL;
> for (j = 0; j < count; ) {
> t1 = measure(99, b);
> if (t1 == ~0UL) continue;
> if (t1 < tmin) tmin = t1;
> tb += t1 % count;
> if (tb >= count) { ++ta; tb -= count; }
> ta += t1 / count;
> ++j;
> }
> printf("%2d %10lu %10lu\n", i, ta, tmin);
> }
> return 0;
> }
This archive was generated by hypermail 2b30 : Sun May 27 2001 - 08:12:36 PDT