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.
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=269327
9
share/examples/hwpmc/Makefile
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9
share/examples/hwpmc/Makefile
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# $FreeBSD$
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PROG= overhead
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LDFLAGS+= -lpmc
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MAN=
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install:
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.include <bsd.prog.mk>
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@ -3,6 +3,4 @@
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Examples illustrating the use of the hwpmc(4) driver and pmc(3)
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library interface.
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While there is nothing here yet, the source code for pmccontrol(8)
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and pmcstat(8) could serve as examples.
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115
share/examples/hwpmc/overhead.c
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115
share/examples/hwpmc/overhead.c
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/*
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* Copyright (c) 2014, Neville-Neil Consulting
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* Neither the name of Neville-Neil Consulting nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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* Author: George V. Neville-Neil
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*
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*
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*/
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#ifndef lint
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static char rcsid [] = "$Header:$" ;
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#endif
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/*
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* Calculate the time overhead of starting, stopping, and recording
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* pmc counters.
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*
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* The only argument is a counter name, such as "instruction-retired"
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* which is CPU dependent and can be found with pmmcontrol(8) using
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* pmccontrol -L.
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*
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* The start, stop, read and write operations are timed using the
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* rdtsc() macro which reads the Time Stamp Counter on the CPU.
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*/
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#include <stdio.h>
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#include <err.h>
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#include <sysexits.h>
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#include <sys/types.h>
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#include <machine/cpufunc.h>
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#include <pmc.h>
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int main(int argc, char **argv)
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{
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pmc_id_t pmcid;
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pmc_value_t read_value;
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pmc_value_t read_clear_value;
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uint64_t tsc1, write_cyc, start_cyc, read_cyc, stop_cyc;
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char *counter_name;
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if (argc != 2)
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err(EX_USAGE, "counter-name required");
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counter_name = argv[1];
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if (pmc_init() != 0)
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err(EX_OSERR, "hwpmc(4) not loaded, kldload or update your kernel");
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if (pmc_allocate(counter_name, PMC_MODE_SC, 0, 0, &pmcid) < 0)
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err(EX_OSERR, "failed to allocate %s as a system counter in counting mode",
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counter_name);
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tsc1 = rdtsc();
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if (pmc_write(pmcid, 0) < 0)
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err(EX_OSERR, "failed to zero counter %s", counter_name);
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write_cyc = rdtsc() - tsc1;
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tsc1 = rdtsc();
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if (pmc_start(pmcid) < 0)
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err(EX_OSERR, "failed to start counter %s", counter_name);
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start_cyc = rdtsc() - tsc1;
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tsc1 = rdtsc();
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if (pmc_read(pmcid, &read_value) < 0)
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err(EX_OSERR, "failed to read counter %s", counter_name);
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read_cyc = rdtsc() - tsc1;
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tsc1 = rdtsc();
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if (pmc_stop(pmcid) < 0)
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err(EX_OSERR, "failed to stop counter %s", counter_name);
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stop_cyc = rdtsc() - tsc1;
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if (pmc_rw(pmcid, 0, &read_clear_value))
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err(EX_OSERR, "failed to read and zero %s", counter_name);
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if (pmc_release(pmcid) < 0)
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err(EX_OSERR, "failed to release %s as a system counter in counting mode",
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counter_name);
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printf("Counter %s, read value %ld, read/clear value %ld\n",
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counter_name, read_value, read_clear_value);
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printf("Cycles to start: %ld\tstop: %ld\tread: %ld\twrite: %ld\n",
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start_cyc, stop_cyc, read_cyc, stop_cyc);
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}
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