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57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
/*
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* Copyright (c) 2011 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* benchctxswitch.c
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* Benchmarks the speed of context switches.
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*/
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#include <err.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <signal.h>
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#include <unistd.h>
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#include <time.h>
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static int uptime(uintmax_t* usecs)
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{
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struct timespec uptime;
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if ( clock_gettime(CLOCK_BOOTTIME, &uptime) < 0 )
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return -1;
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*usecs = uptime.tv_sec * 1000000ULL + uptime.tv_nsec / 1000ULL;
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return 0;
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}
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int main(void)
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{
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pid_t slavepid = fork();
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if ( slavepid < 0 )
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err(1, "fork");
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if ( slavepid == 0 ) { while ( true ) { usleep(0); } exit(0); }
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uintmax_t start;
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if ( uptime(&start) )
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err(1, "uptime");
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uintmax_t end = start + 1ULL * 1000ULL * 1000ULL; // 1 second
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size_t count = 0;
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uintmax_t now;
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while ( !uptime(&now) && now < end ) { usleep(0); count += 2; /* back and forth */ }
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printf("Made %zu context switches in 1 second\n", count);
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kill(slavepid, SIGKILL);
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return 0;
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}
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