Provided by: rt-tests_1.0-3_amd64 
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)