| LIKWID-PERFCTR(1) | General Commands Manual | LIKWID-PERFCTR(1) |
likwid-perfctr - configure and read out hardware performance counters on x86, ARM and POWER CPUs and Nvidia GPUs
likwid-perfctr [-vhHmaiefO] [-c core_list] [-C core_list_for_pinning] [-g performance_group or performance_event_string] [-t timeline_frequency] [-S monitoring_time] [-T group_switch_frequency] [-V verbosity] [-M access_mode] [-o output_file] [-s skip_mask] [-E search_str] [--stats]
likwid-perfctr is a lightweight command line application to configure and read out hardware performance monitoring data on supported x86, ARM and POWER processors. It can measure either as wrapper without changing the measured application or with marker API functions inside the code, which will turn on and off the counters. There are preconfigured performance groups with useful event sets and derived metrics. Additionally, arbitrary events can be measured with custom event sets. The marker API can measure multiple named regions and the results are accumulated over multiple region calls.
Because likwid-perfctr measures on processors and not single applications it is necessary to ensure that processes and threads are pinned to dedicated resources. You can either pin the application yourself or use the builtin pin functionality.
The parent process is pinned to processor 0, Thread 0 to processor 1 and Thread 1 to processor 2.
It is specified that the event INSTRUCTIONS_RETIRED_SSE is measured on counter PMC0 and the event CPU_CLOCKS_UNHALTED on counter PMC3. It is possible calculate the run time of all threads based on the CPU_CLOCKS_UNHALTED event. If you want this you have to include this event in your custom event string as shown above.
On Intel processors fixed events are measured on dedicated counters. These are INSTR_RETIRED_ANY and CPU_CLK_UNHALTED_CORE. If you configure these fixed counters, likwid-perfctr will calculate the run time and CPI metrics for your run.
You have to link you code against liblikwid.so and use the marker API calls. Examples can be found in examples folder /usr/share/likwid/examples. The following code snippet shows the necessary calls:
#include <likwid-marker.h> /* only one thread calls init */ LIKWID_MARKER_INIT; /* Can be called by each thread the should
* perform measurements. It is only needed
* if the pinning feature of LIKWID failed
* and the threads need to be pinned explicitly.
*
* If you place it in the same parallel
* region as LIKWID_MARKER_START, perform a
* barrier between the statements to avoid
* timing problems.
*/ LIKWID_MARKER_THREADINIT; /* If you run the code region only once, register
* the region tag previously to reduce the overhead
* of START and STOP calls. Call it once for each
* thread in parallel environment.
* Note: No whitespace characters are allowed in the region tags
* This call is optional but RECOMMENDED, START will do the same operations.
*/ LIKWID_MARKER_REGISTER("name"); /* Start measurement
* Note: No whitespace characters are allowed in the region tags
*/ LIKWID_MARKER_START("name"); /*
* Your code to be measured is here
* You can also nest named regions
* No whitespaces are allowed in the region names!
*/ LIKWID_MARKER_STOP("name"); /* If you want to measure multiple groups/event sets
* Switches through groups in round-robin fashion
*/ LIKWID_MARKER_SWITCH; /* If you want to get the data of a region inside your application
* nevents in an (int*) and used as input length of the events array. After the
* call, nevents contains the actual amount of events
* events is an array of doubles (double*), time is a pointer to double to
* retrieve the measured runtime of the region and count is a pointer to int
* and is filled with the call count of the region.
*/ LIKWID_MARKER_GET("name", nevents, events, time, count); /* If you want to reset the counts for a region
*/ LIKWID_MARKER_RESET("name"); /* Finally */ LIKWID_MARKER_CLOSE;
This will read out the counters every 300ms on physical hardware threads 0-3 and write the results to out.txt. The application is not pinned to the CPUs. The output syntax of the timeline mode is for custom event sets:
<groupID> <numberOfEvents> <numberOfThreads> <Timestamp> <Event1_Thread1> <Event2_Thread1> ... <Event1_Thread2> ... <EventN_ThreadM>
For performance groups with metrics: <groupID> <numberOfMetrics> <numberOfThreads> <Timestamp> <Metric1_Thread1> <Metric2_Thread1> ... <Metric1_Thread2> ...<MetricN_ThreadM>
For timeline mode there is a frontend application likwid-perfscope(1), which enables live plotting of selected events. Please be aware that with high frequencies (<100ms), the values differ from the real results but the behavior of them is valid.
This will start the counters and read them out after 2s on physical hardware threads 0-3 and write the results to stdout.
This will program the counter CBOX0C0 (the counter 0 of the LLC cache box 0) to measure the event LLC_LOOKUPS_DATA_READ and filter the increments by the state of a cacheline. STATE=0x9 for this event means all <invalid> and <modified> cachelines. Which options are allowed for which box is listed in LIKWID's html documentation. The values for the options can be found in the vendors performance monitoring documentations. Likwid measures the first CPU of socket 0 and the first CPU of socket 1. See likwid-pin(1) for details regarding the cpu expressions. For more code examples have a look at the likwid WIKI pages and LIKWID's html documentation.
This runs the application in NvMarkerAPI mode on GPUs 0 and 1 and measures the single-precision flops. The NvMarkerAPI is similar to the CPU MarkerAPI (compile -DLIKWID_NVMON):
#include <likwid-marker.h>
/* Initialize the library and add configured eventset */ LIKWID_NVMARKER_INIT;
/* If you run the code region only once, register
* the region tag previously to reduce the overhead
* of START and STOP calls. Call it before calling START() for
* the region the first time.
*
* Place it around your CUDA kernel call.
*
* Note: No whitespace characters are allowed in the region tags
* This call is optional but RECOMMENDED, START will do the same operations.
*/ LIKWID_NVMARKER_REGISTER("name");
/* Start measurement on Nvidia GPUs
* Note: No whitespace characters are allowed in the region tags
*/ LIKWID_NVMARKER_START("name"); /*
* Your code to be measured is here
* You can also nest named regions
*/
/* Stop measurment on Nvidia GPUs
* No whitespaces are allowed in the region names!
*/ LIKWID_NVMARKER_STOP("name");
/* If you want to measure multiple groups/event sets
* Switches through groups in round-robin fashion.
*/ LIKWID_NVMARKER_SWITCH;
/* If you want to get the data of a region inside your application
* nevents in an (int*) and used as input length of the events array. After
the
* call, nevents contains the actual amount of events. Same for ngpus.
* events is an array of doubles (double*), time is a pointer to double to
* retrieve the measured runtime of the region and count is a pointer to int
* and is filled with the call count of the region.
*/ LIKWID_NVMARKER_GET("name", ngpus, nevents, events, time,
count);
/* If you want to reset the counts for a region
*/ LIKWID_NVMARKER_RESET("name");
/* Finally */ LIKWID_NVMARKER_CLOSE;
Written by Thomas Gruber <thomas.roehl@googlemail.com>.
Report Bugs on <https://github.com/RRZE-HPC/likwid/issues>.
likwid-topology(1), likwid-perfscope(1), likwid-pin(1), likwid-bench(1)
| 16.11.2020 | likwid-5 |