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Subjectqsbench

I've rewritten the "qsort test" again, now it uses its own qsort
and it's much faster than the previous qs.c.
Renamed qs.c to qsbench.c :)
Previous results are not comparable.
Three sequential runs of qsbench with the same seed = 140175100

Results below, qsbench.c code to the end.

Linux-2.4.11-pre5:

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
70.950u 1.890s 2:20.41 51.8% 0+0k 0+0io 10671pf+0w

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
71.370u 1.610s 2:20.85 51.8% 0+0k 0+0io 10591pf+0w

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
70.870u 1.700s 2:20.99 51.4% 0+0k 0+0io 10587pf+0w


Linux-2.4.10-ac9:

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
70.940u 2.420s 3:21.21 36.4% 0+0k 0+0io 12745pf+0w

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
72.240u 3.250s 4:01.99 31.1% 0+0k 0+0io 15616pf+0w

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
71.530u 2.560s 3:33.09 34.7% 0+0k 0+0io 13095pf+0w


Linux-2.4.10-ac9 + Rik's eatcache patch:

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
71.680u 2.410s 3:30.48 35.2% 0+0k 0+0io 12603pf+0w

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
72.070u 2.460s 3:53.87 31.8% 0+0k 0+0io 15361pf+0w

time ./qsbench -n 90000000 -p 1 -s 140175100
seed = 140175100
71.240u 2.940s 4:36.24 26.8% 0+0k 0+0io 17801pf+0w


I would say qsbench can't give a definitive answer on this
patch because results are not enough reproducible.
Maybe qsbench is not even suited to test this patch, I suspect.
Anyway, here's the qsbench.c new code,


/*
* Copyright (C) 2001 Lorenzo Allegrucci (lenstra@tiscalinet.it)
* Licensed under the GPL
*/
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#define MAX_PROCS 1024

/**
* quick_sort - Sort in the range [l, r]
*/
void quick_sort(int a[], int l, int r)
{
int i, j, p, tmp;
int m, min, max;

i = l;
j = r;
m = (l + r) >> 1;

if (a[m] >= a[l]) {
max = a[m];
min = a[l];
} else {
max = a[l];
min = a[m];
}

if (a[r] >= max)
p = max;
else {
if (a[r] >= min)
p = a[r];
else
p = min;
}

do {
while (a[i] < p)
i++;

while (p < a[j])
j--;

if (i <= j) {
tmp = a[i];
a[i] = a[j];
a[j] = tmp;
i++;
j--;
}
} while (i <= j);

if (l < j)
quick_sort(a, l, j);

if (i < r)
quick_sort(a, i, r);
}


void do_qsort(int n, int s)
{
int * a, i, errors = 0;

if ((a = malloc(sizeof(int) * n)) == NULL) {
perror("malloc");
exit(1);
}

srand(s);
printf("seed = %d\n", s);

for (i = 0; i < n; i++)
a[i] = rand();

quick_sort(a, 0, n - 1);

for (i = 0; i < n - 1; i++)
if (a[i] > a[i + 1])
errors++;
if (errors)
fprintf(stderr, "WARNING: %d errors.\n", errors);
free(a);
exit(0);
}


void start_procs(int n, int p, int s)
{
int i, pid[MAX_PROCS];
int status;

if (p > MAX_PROCS)
p = MAX_PROCS;

for (i = 0; i < p; i++) {
pid[i] = fork();
if (pid[i] == 0)
do_qsort(n, s);
else if (pid[i] < 0)
perror("fork");
}

for (i = 0; i < p; i++)
waitpid(pid[i], &status, 0);
}

void usage(void)
{
fprintf(stderr, "Usage: qs [-h] [-n nr_elems] [-p nr_procs]"
" [-s seed]\n");
exit(1);
}


int main(int argc, char * argv[])
{
char * n = NULL, * p = NULL, * s = NULL;
int nr_elems = 1000000, nr_procs = 1, seed = 1;
int c;

if (argc == 1)
usage();

while (1) {
c = getopt(argc, argv, "hn:p:s:V");
if (c == -1)
break;

switch (c) {
case 'h':
usage();
case 'n':
n = optarg;
nr_elems = atoi(n);
break;
case 'p':
p = optarg;
nr_procs = atoi(p);
break;
case 's':
s = optarg;
seed = atoi(s);
break;
case 'V':
printf("Version 0.92\n");
return 1;
case '?':
return 1;
}
}

start_procs(nr_elems, nr_procs, seed);

return 0;
}



--
Lorenzo

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