Date: Thu, 31 Jul 2014 09:18:16 +0000 (UTC) From: "George V. Neville-Neil" <gnn@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r269327 - head/share/examples/hwpmc Message-ID: <201407310918.s6V9IG8O072166@svn.freebsd.org>
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Author: gnn Date: Thu Jul 31 09:18:15 2014 New Revision: 269327 URL: http://svnweb.freebsd.org/changeset/base/269327 Log: Add an example program to show how to use libpmc from a program. This particular program attempts to use the TSC to measure how long certainly libpmc operations take. Depending on the quality of the rdtsc() macro on a particular architecture this may work more or less well. Added: head/share/examples/hwpmc/Makefile (contents, props changed) head/share/examples/hwpmc/overhead.c (contents, props changed) Modified: head/share/examples/hwpmc/README Added: head/share/examples/hwpmc/Makefile ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/share/examples/hwpmc/Makefile Thu Jul 31 09:18:15 2014 (r269327) @@ -0,0 +1,9 @@ +# $FreeBSD$ + +PROG= overhead +LDFLAGS+= -lpmc +MAN= + +install: + +.include <bsd.prog.mk> Modified: head/share/examples/hwpmc/README ============================================================================== --- head/share/examples/hwpmc/README Thu Jul 31 08:28:42 2014 (r269326) +++ head/share/examples/hwpmc/README Thu Jul 31 09:18:15 2014 (r269327) @@ -3,6 +3,4 @@ Examples illustrating the use of the hwpmc(4) driver and pmc(3) library interface. -While there is nothing here yet, the source code for pmccontrol(8) -and pmcstat(8) could serve as examples. Added: head/share/examples/hwpmc/overhead.c ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/share/examples/hwpmc/overhead.c Thu Jul 31 09:18:15 2014 (r269327) @@ -0,0 +1,115 @@ +/* + * Copyright (c) 2014, Neville-Neil Consulting + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * 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. + * + * Neither the name of Neville-Neil Consulting nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT + * OWNER 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. + * + * $FreeBSD$ + * + * Author: George V. Neville-Neil + * + * + */ + +#ifndef lint +static char rcsid [] = "$Header:$" ; +#endif + +/* + * Calculate the time overhead of starting, stopping, and recording + * pmc counters. + * + * The only argument is a counter name, such as "instruction-retired" + * which is CPU dependent and can be found with pmmcontrol(8) using + * pmccontrol -L. + * + * The start, stop, read and write operations are timed using the + * rdtsc() macro which reads the Time Stamp Counter on the CPU. + */ + +#include <stdio.h> +#include <err.h> +#include <sysexits.h> +#include <sys/types.h> +#include <machine/cpufunc.h> +#include <pmc.h> + +int main(int argc, char **argv) +{ + pmc_id_t pmcid; + pmc_value_t read_value; + pmc_value_t read_clear_value; + uint64_t tsc1, write_cyc, start_cyc, read_cyc, stop_cyc; + char *counter_name; + + if (argc != 2) + err(EX_USAGE, "counter-name required"); + + counter_name = argv[1]; + + if (pmc_init() != 0) + err(EX_OSERR, "hwpmc(4) not loaded, kldload or update your kernel"); + + if (pmc_allocate(counter_name, PMC_MODE_SC, 0, 0, &pmcid) < 0) + err(EX_OSERR, "failed to allocate %s as a system counter in counting mode", + counter_name); + + tsc1 = rdtsc(); + if (pmc_write(pmcid, 0) < 0) + err(EX_OSERR, "failed to zero counter %s", counter_name); + write_cyc = rdtsc() - tsc1; + + tsc1 = rdtsc(); + if (pmc_start(pmcid) < 0) + err(EX_OSERR, "failed to start counter %s", counter_name); + start_cyc = rdtsc() - tsc1; + + tsc1 = rdtsc(); + if (pmc_read(pmcid, &read_value) < 0) + err(EX_OSERR, "failed to read counter %s", counter_name); + read_cyc = rdtsc() - tsc1; + + tsc1 = rdtsc(); + if (pmc_stop(pmcid) < 0) + err(EX_OSERR, "failed to stop counter %s", counter_name); + stop_cyc = rdtsc() - tsc1; + + if (pmc_rw(pmcid, 0, &read_clear_value)) + err(EX_OSERR, "failed to read and zero %s", counter_name); + + if (pmc_release(pmcid) < 0) + err(EX_OSERR, "failed to release %s as a system counter in counting mode", + counter_name); + + printf("Counter %s, read value %ld, read/clear value %ld\n", + counter_name, read_value, read_clear_value); + printf("Cycles to start: %ld\tstop: %ld\tread: %ld\twrite: %ld\n", + start_cyc, stop_cyc, read_cyc, stop_cyc); + +} +
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