NAME

       hackbench - scheduler benchmark/stress test

SYNOPSIS

       hackbench   [-p|--pipe]  [-s|--datasize  <bytes>]  [-l|--loops  <num-loops>]  [-g|--groups
       <num-groups>] [-f|--fds <num-fds>] [-T|--threads] [-P|--process] [--help]

DESCRIPTION

       Hackbench is both a benchmark and a stress test for the Linux kernel scheduler. It's  main
       job  is  to  create a specified number of pairs of schedulable entities (either threads or
       traditional processes) which communicate via either sockets or pipes and time how long  it
       takes for each pair to send data back and forth.

OPTIONS

       These  programs  follow the usual GNU command line syntax, with long options starting with
       two dashes ("--").
       A summary of options is included below.

       -p, --pipe
              Sends the data via a pipe instead of the socket (default)

       -s, --datasize=<size in bytes>
              Sets the amount of data to send in each message

       -l, --loops=<number of loops>
              How many messages each sender/receiver pair should send

       -g, --groups=<number of groups>
              Defines how many groups of senders and receivers should be started

       -f, --fds=<number of file descriptors>
              Defines how many file descriptors each child should use.  Note that  the  effective
              number  will  be twice the amount you set here, as the sender and receiver children
              will each open the given amount of file descriptors.

       -T, --threads
              Each sender/receiver child will be a POSIX thread of the parent.

       -P, --process
              Hackbench will use fork() on all children (default behaviour)

       --help
              Shows a simple help screen

EXAMPLES

       Running hackbench without any options  will  give  default  behaviour,  using  fork()  and
       sending data between senders and receivers via sockets.

       user@host: ~ $ hackbench
       Running in process mode with 10 groups using 40 file descriptors each (== 400 tasks)
       Each sender will pass 100 messages of 100 bytes
       Time: 0.890

       To use pipes between senders and receivers and using threads instead of fork(), run

       user@host: ~ $ hackbench --pipe --threads   (or hackbench -p -T)
       Running in threaded mode with 10 groups using 40 file descriptors each (== 400 tasks)
       Each sender will pass 100 messages of 100 bytes
       Time: 0.497

       Set the datasize to 512 bytes, do 200 messages per sender/receiver pairs and use 15 groups
       using 25 file descriptors per child, in process mode.

       user@host: ~ $ hackbench -s 512 -l 200 -g 15 -f 25 -P
       Running in process mode with 15 groups using 50 file descriptors each (== 750 tasks)
       Each sender will pass 200 messages of 512 bytes
       Time: 4.497

AUTHORS

       hackbench was written by Rusty Russell  <rusty@rustcorp.com.au>  with  contributions  from
       Yanmin   Zhang  <yanmin_zhang@linux.intel.com>,  Ingo  Molnar  <mingo@elte.hu>  and  David
       Sommerseth <davids@redhat.com>

       This manual page was written by Clark Williams <williams@redhat.com> and David  Sommerseth
       <davids@redhat.com>

HISTORY

       This    version    of    hackbench    is    based    on    the    code   downloaded   from
       http://people.redhat.com/mingo/cfs-scheduler/tools/hackbench.c.  Yanmin Zhang  merged  the
       original hackbench code from
       http://devresources.linuxfoundation.org/craiger/hackbench/src/hackbench.c    which    uses
       fork() and a modified version from
       http://www.bullopensource.org/posix/pi-futex/hackbench_pth.c which uses pthread  only  and
       gave  the  possibility  to  change  behaviour at run time.  Hackbench have since then gone
       through some more rewriting to improve error handling  and  proper  tracking  of  fork()ed
       children, to avoid leaving zombies on the system if hackbench stops unexpectedly.

                                        February  23, 2010                           hackbench(8)