Date: Wed, 3 Sep 2014 17:26:47 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r271044 - head/tools/tools/tscdrift Message-ID: <201409031726.s83HQlMM048946@svn.freebsd.org>
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Author: jhb Date: Wed Sep 3 17:26:46 2014 New Revision: 271044 URL: http://svnweb.freebsd.org/changeset/base/271044 Log: Import a hackish tool I use to examine the skew of the TSC across CPUs in a system. The tool queries the kernel for its set of CPUs and compares TSC values on each of the additional CPUs to the first CPU in turn. It then outputs a table of simple statistics. Added: head/tools/tools/tscdrift/ head/tools/tools/tscdrift/Makefile (contents, props changed) head/tools/tools/tscdrift/tscdrift.c (contents, props changed) Added: head/tools/tools/tscdrift/Makefile ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/tools/tools/tscdrift/Makefile Wed Sep 3 17:26:46 2014 (r271044) @@ -0,0 +1,10 @@ +# $FreeBSD$ + +PROG= tscdrift +MAN= +WARNS?= 6 + +LDADD= -lpthread -lm +DPADD= ${LIBPTHREAD} ${LIBM} + +.include <bsd.prog.mk> Added: head/tools/tools/tscdrift/tscdrift.c ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/tools/tools/tscdrift/tscdrift.c Wed Sep 3 17:26:46 2014 (r271044) @@ -0,0 +1,193 @@ +/*- + * Copyright (c) 2014 Advanced Computing Technologies LLC + * Written by: John H. Baldwin <jhb@FreeBSD.org> + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/param.h> +#include <sys/cpuset.h> +#include <machine/atomic.h> +#include <machine/cpu.h> +#include <machine/cpufunc.h> +#include <assert.h> +#include <err.h> +#include <errno.h> +#include <math.h> +#include <pthread.h> +#include <stdint.h> +#include <stdlib.h> +#include <stdio.h> + +#define barrier() __asm __volatile("" ::: "memory") + +#define TESTS 1024 + +static volatile int gate; +static volatile uint64_t thread_tsc; + +/* Bind the current thread to the specified CPU. */ +static void +bind_cpu(int cpu) +{ + cpuset_t set; + + CPU_ZERO(&set); + CPU_SET(cpu, &set); + if (cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TID, -1, sizeof(set), + &set) < 0) + err(1, "cpuset_setaffinity(%d)", cpu); +} + +static void * +thread_main(void *arg) +{ + int cpu, i; + + cpu = (intptr_t)arg; + bind_cpu(cpu); + for (i = 0; i < TESTS; i++) { + gate = 1; + while (gate == 1) + cpu_spinwait(); + barrier(); + + __asm __volatile("lfence"); + thread_tsc = rdtsc(); + + barrier(); + gate = 3; + while (gate == 3) + cpu_spinwait(); + } + return (NULL); +} + +int +main(int ac __unused, char **av __unused) +{ + cpuset_t all_cpus; + int64_t **skew, *aveskew, *minskew, *maxskew; + float *stddev; + double sumsq; + pthread_t child; + uint64_t tsc; + int *cpus; + int error, i, j, ncpu; + + /* + * Find all the CPUs this program is eligible to run on and use + * this as our global set. This means you can use cpuset to + * restrict this program to only run on a subset of CPUs. + */ + if (cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID, -1, + sizeof(all_cpus), &all_cpus) < 0) + err(1, "cpuset_getaffinity"); + for (ncpu = 0, i = 0; i < CPU_SETSIZE; i++) { + if (CPU_ISSET(i, &all_cpus)) + ncpu++; + } + if (ncpu < 2) + errx(1, "Only one available CPU"); + cpus = calloc(ncpu, sizeof(*cpus)); + skew = calloc(ncpu, sizeof(*skew)); + for (i = 0; i < ncpu; i++) + skew[i] = calloc(TESTS, sizeof(*skew[i])); + for (i = 0, j = 0; i < CPU_SETSIZE; i++) + if (CPU_ISSET(i, &all_cpus)) { + assert(j < ncpu); + cpus[j] = i; + j++; + } + + /* + * We bind this thread to the first CPU and then bind all the + * other threads to other CPUs in turn saving TESTS counts of + * skew calculations. + */ + bind_cpu(cpus[0]); + for (i = 1; i < ncpu; i++) { + error = pthread_create(&child, NULL, thread_main, + (void *)(intptr_t)cpus[i]); + if (error) + errc(1, error, "pthread_create"); + + for (j = 0; j < TESTS; j++) { + while (gate != 1) + cpu_spinwait(); + gate = 2; + barrier(); + + tsc = rdtsc(); + + barrier(); + while (gate != 3) + cpu_spinwait(); + gate = 4; + + skew[i][j] = thread_tsc - tsc; + } + + error = pthread_join(child, NULL); + if (error) + errc(1, error, "pthread_join"); + } + + /* + * Compute average skew for each CPU and output a summary of + * the results. + */ + aveskew = calloc(ncpu, sizeof(*aveskew)); + minskew = calloc(ncpu, sizeof(*minskew)); + maxskew = calloc(ncpu, sizeof(*maxskew)); + stddev = calloc(ncpu, sizeof(*stddev)); + stddev[0] = 0.0; + for (i = 1; i < ncpu; i++) { + sumsq = 0; + minskew[i] = maxskew[i] = skew[i][0]; + for (j = 0; j < TESTS; j++) { + aveskew[i] += skew[i][j]; + if (skew[i][j] < minskew[i]) + minskew[i] = skew[i][j]; + if (skew[i][j] > maxskew[i]) + maxskew[i] = skew[i][j]; + sumsq += (skew[i][j] * skew[i][j]); + } + aveskew[i] /= TESTS; + sumsq /= TESTS; + sumsq -= aveskew[i] * aveskew[i]; + stddev[i] = sqrt(sumsq); + } + + printf("CPU | TSC skew (min/avg/max/stddev)\n"); + printf("----+------------------------------\n"); + for (i = 0; i < ncpu; i++) + printf("%3d | %5jd %5jd %5jd %6.3f\n", cpus[i], + (intmax_t)minskew[i], (intmax_t)aveskew[i], + (intmax_t)maxskew[i], stddev[i]); + return (0); +}
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