Self-contained C/C++ profiler library for Linux.
Prof offers a quick way to measure performance events (CPU clock cycles,
cache misses, branch mispredictions, etc.) of C/C++ code snippets. Prof is
just a wrapper around the perf_event_open
system call, its main goal is to
be easy to setup and painless to use for targeted optimizations, namely, when
the hot spot has already been identified. In no way Prof is a replacement for
a fully-fledged profiler like perf, gprof, callgrind, etc.
Please be aware that Prof uses __attribute__((constructor))
to be as more
straightforward to setup as possible, so it cannot be included more than
once.
The following snippet prints the rough number of CPU clock cycles spent in executing the code between the two Prof calls:
#include "prof.h"
int main()
{
PROF_START();
// slow code goes here...
PROF_STDOUT();
}
The following snippet instead counts both read and write faults of the level 1 data cache that occur in the userland code between the two Prof calls:
#include <stdio.h>
#define PROF_USER_EVENTS_ONLY
#define PROF_EVENT_LIST \
PROF_EVENT_CACHE(L1D, READ, MISS) \
PROF_EVENT_CACHE(L1D, WRITE, MISS)
#include "prof.h"
int main()
{
uint64_t faults[2] = { 0 };
PROF_START();
// slow code goes here...
PROF_DO(faults[index] += counter);
// fast or uninteresting code goes here...
PROF_START();
// slow code goes here...
PROF_DO(faults[index] += counter);
printf("Total L1 faults: R = %lu; W = %lu\n", faults[0], faults[1]);
}
Just include prof.h
. Here is a quick way to fetch the latest version:
wget -q https://raw.githubusercontent.com/cyrus-and/prof/master/prof.h
Since Prof uses perf_event_open
make sure to have the permission to access
the performance counters: either run the program as superuser (discouraged)
or set the value of perf_event_paranoid
appropriately, for example:
$ echo 1 | sudo tee /proc/sys/kernel/perf_event_paranoid
Optionally make it permanent with:
$ echo 'kernel.perf_event_paranoid=1' | sudo tee /etc/sysctl.d/local.conf
See man perf_event_open
for more information.
Reset the counters and (re)start counting the events.
The events to be monitored are specified by setting the PROF_EVENT_LIST
macro before including this file to a list of PROF_EVENT_*
invocations;
defaults to counting the number CPU clock cycles.
If the PROF_USER_EVENTS_ONLY
macro is defined before including this file
then kernel and hypervisor events are excluded from the count.
Specify an event to be monitored, type
and config
are defined in the
documentation of the perf_event_open
system call.
Same as PROF_EVENT
but for hardware events; prefix PERF_COUNT_HW_
must be
omitted from config
.
Same as PROF_EVENT
but for software events; prefix PERF_COUNT_SW_
must be
omitted from config
.
Same as PROF_EVENT
but for cache events; prefixes PERF_COUNT_HW_CACHE_
,
PERF_COUNT_HW_CACHE_OP_
and PERF_COUNT_HW_CACHE_RESULT_
must be omitted
from cache
, op
and result
, respectively. Again cache
, op
and
result
are defined in the documentation of the perf_event_open
system
call.
Stop counting the events. The counter array can then be accessed with
PROF_COUNTERS
.
Access the counter array. The order of counters is the same of the events
defined in PROF_EVENT_LIST
. Elements of this array are 64 bit unsigned
integers.
Stop counting the events and execute the code provided by block
for each
event. Within code
: index
refers to the event position index in the
counter array defined by PROF_COUNTERS
; counter
is the actual value of
the counter. index
is a 64 bit unsigned integer.
Same as PROF_DO
except that callback
is the name of a callable object
(e.g. a function) which, for each event, is be called with the two parameters
index
and counter
.
Stop counting the events and write to file
(a stdio.h FILE *
) as many
lines as are events in PROF_EVENT_LIST
. Each line contains index
and
counter
(as defined by PROF_DO
) separated by a tabulation character. If
there is only one event then index
is omitted.
Same as PROF_LOG_FILE
except that file
is stdout
.
Same as PROF_LOG_FILE
except that file
is stderr
.
Copyright (c) 2020 Andrea Cardaci cyrus.and@gmail.com
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.