Ubuntu Manpage: likwid-bench - low-level benchmark suite and microbenchmarking framework

NAME

       likwid-bench - low-level benchmark suite and microbenchmarking framework

SYNOPSIS

       likwid-bench    [-hap]    [-t    <testname>]    [-s    <min_time>]    [-w   <workgroup_expression>]   [-W
       <workgroup_expression_short>] [-l <testname>] [-d <delimiter>] [-i <iterations>] [-f <filepath>]

DESCRIPTION

       likwid-bench is a  benchmark  suite  for  low-level  (assembly)  benchmarks  to  measure  bandwidths  and
       instruction  throughput  for  specific  instruction code on x86 systems. The currently included benchmark
       codes include common data access patterns like load and store but also calculations like vector triad and
       sum.   likwid-bench  includes architecture specific benchmarks for x86, x86_64 and x86 for Intel Xeon Phi
       coprocessors. With LIKWID 5 also ARM and POWER benchmarks  are  supported.  The  performance  values  can
       either  be calculated by likwid-bench or measured using performance counters by using likwid-perfctr as a
       wrapper to likwid-bench.  This requires to build likwid-bench with instrumentation enabled in  config.mk.
       Benchmarks    can    be    dynamically    added    when    a    proper    ptt    file   is   present   at
       $HOME/.likwid/bench/<arch>/<testname>.ptt . The files are compiled to a .S file and compiled using either
       gcc,  icc  or  pgcc (searched in $PATH). The default folder is /tmp/<PID>. Possible values for <arch> are
       'x86', 'x86-64', 'phi', armv7', 'armv8' and 'power'.

OPTIONS

       -h     prints a help message to standard output, then exits.

       -a     list available benchmark codes for the current system.

       -p     list available thread domains.

       -s <min_time>
              Run the benchmark for at least <min_time> seconds.  The amount of iterations is  determined  using
              this value. Default: 1 second.

       -t <testname>
              Name of the benchmark code to run (mandatory).

       -w <workgroup_expression>
              Specify  the  affinity domain, thread count and data set size for the current benchmarking run (-w
              or -W mandatory). First thread in thread domain initializes the stream.

       -W <workgroup_expression_short>
              Specify the affinity domain, thread count and data set size for the current benchmarking  run  (-w
              or -W mandatory). Each thread in the workgroup initializes its own chunk of the stream.

       -l <testname>
              list properties of a benchmark code.

       -i <iterations>
              Set the number of iterations per thread (optional)

       -f <filepath>
              Filepath for the dynamic generation of benchmarks. Default /tmp/. <PID> is always attached

WORKGROUP SYNTAX

       <thread_domain>:<size>  [:<num_threads>[:<chunk_size>:<stride>]]  [-<streamId>:<domain_id>]  with size in
       kB, MB or GB. The <thread_domain> defines where the threads are placed.  <size> is  the  total  data  set
       size for the benchmark, the allocated vectors in memory sum up to this size.  <num_threads> specifies how
       many threads are used in the <thread_domain>.  Threads are  always  placed  using  a  compact  policy  in
       likwid-bench.   This means that per default all SMT threads are used. Optionally similar a the expression
       based syntax in likwid-pin a <chunk_size> and <stride> can  be  provided.  Optionally  for  every  stream
       (array,  vector)  the  placement  can  be  controlled.  Per  default  all  arrays  are placed in the same
       <thread_domain> the threads are running in. To place the data in a different domain for every stream of a
       benchmark  case  (the  total  number of streams can be acquired by the -l option) the domain to place the
       data in can be specified. Multiple streams are comma separated. Either the placement is provided  or  all
       streams  have  to  be  explicitly  placed.  Please  refer  to  the Wiki pages on https://github.com/RRZE-
       HPC/likwid/wiki/Likwid-Bench for further details and examples on usage.  With -W each thread  initializes
       its own chunk of the streams but pleacement of the streams is deactivated.

EXAMPLE

1. Run the copy benchmark on socket 0 ( S0 ) with a total data set size of 100kB.

likwid-bench -t copy -w S0:100kB

Since no <num_threads> is given in the workload expression, each core of socket 0 gets one thread. The
workload is split up between all threads and the number of iterations is determined automatically.

2. Run the triad benchmark code with explicitly 100 iterations per thread with 2 threads on the socket 0
( S0 ) and a data size of 1GB.

likwid-bench -t triad -i 100 -w S0:1GB:2:1:2

Assuming socket 0 ( S0 ) has 2 physical cores with SMT enabled, hence in total 4 hardware threads, one
thread is assigned to each physical core of socket 0.

3. Run the update benchmark on socket 0 ( S0 ) with a workload of 100kB and on socket 1 ( S1 ) with the
same workload.

likwid-bench -t update -w S0:100kB -w S1:100kB

The results of both workgroups are combinded for the output. Hence the workload in each workgroup
expression should have the same size.

4. Run the copy benchmark but measure the memory traffic with likwid-perfctr. The option
INSTRUMENT_BENCH in config.mk needs to be true at compile time to use that feature.

likwid-perfctr -c E:S0:4 -g MEM -m likwid-bench -t update -w S0:100kB

likwid-perfctr will configure and start the performance counters on socket 0 ( S0 ) with 4 threads prior
to the execution of likwid-bench. The performance counters are read right before and after running the
benchmarking code to minimize the interferences of the measurement.

5. Run the copy benchmark and place the data on another socket

likwid-bench -t copy -w S0:1GB:10:1:2-0:S1,1:S1

Stream id 0 and 1 are placed in thread domains S1, which is socket 1. This can be verified as the
initialization threads output where they are running.

WARNING

       Since LIKWID 5.0, it is possible to have different numbers of threads in workgroups. Also different sizes
       are  allowed.  Both features seem promising, but they show a range of problems. If you have a NUMA system
       and run with multiple threads on NUMA node 0 but with less on NUMA node 1, the threads  on  NUMA  node  1
       cause less preassure on the memory interface and consequently achieve higher throughput. They will finish
       early compared to the threads on NUMA node 0. The runtime used for caluclating the bandwidth and MFlops/s
       values  use  the  maximal  runtime of all threads, hence one of NUMA node 0.  Similar problems exist with
       different sizes. One workgroup might run in cache  while  the  other  waits  for  data  from  the  memory
       interface.

AUTHOR

       Written by Thomas Gruber <thomas.roehl@googlemail.com>.

BUGS

       Report Bugs on <https://github.com/RRZE-HPC/likwid/issues>.