BENCHMARK-PERLFORMANCE-SET-STABLE-SYSTEM

NAME

benchmark−perlformance−set−stable−system − CPU scaling utility for Benchmark::Perl::Formance

SYNOPSIS

Usage:

  $ bin/benchmark−perlformance−set−stable−system list
  $ bin/benchmark−perlformance−set−stable−system lo      > ORIG_VALUES_FILE
  $ bin/benchmark−perlformance−set−stable−system hi      > ORIG_VALUES_FILE
  $ bin/benchmark−perlformance−set−stable−system restore < ORIG_VALUES_FILE

It needs root permissions to actually change the cpu settings, so run it with "sudo".

ABOUT

This is an utility to be used from inside benchmark-perlformance in order to prepare a system as stable as possible, but can also be used on its own.

Tries to stabilize a system via:

	•		Setting max frequency of all cpus to the minimal possible cpu frequency (so the system can’t scale down further unexpectedly, e.g. when it gets hot).
	•		Disabling address space randomization ( ASLR ) (https://wiki.ubuntu.com/Security/Features)
	•		Drop caches (http://linux−mm.org/Drop_Caches)
	•		Classical disk sync

COMMANDS

•

list

Prints the current values to STDOUT, in a format readable by the "reset" command.

•

Scales down a system to lowest possible frequency, disables ASLR, flushes caches, calls ’sync’.

Prints the original values to STDOUT, in a format readable by the "reset" command.

•

This tries to be the complement to "lo".

Scales up the system to highest possible frequency (but enables ASLR again which is not really a fast setting).

Prints the original values to STDOUT, in a format readable by the "reset" command.

This isn’t recommended for getting stable benchmark values because a scaled-up system might be forced to scale down automatically by the cpu when it gets too hot, or scale up to turbo mode.

•

restore

Restores the original values, as read from STDIN in a format as produced by the other commands.

FUNCTIONS

proc_value
Get or set value in "/proc" or "/sys" filesystem.

set($hi)
Set the requested stabilization mode. If parameter $hi is true then it sets the max allowed frequency to the maximum (command "hi"), otherwise to the lowest possible value (command "lo").

This sub prints out the original values to STDOUT via Data::Dumper, like it is expected by the "restore" command.

reset
Resets the cpu stabilization to the original values.

It reads these values from STDIN as Data::Dumper format like provided by the set() function.

usage
Prints out usage help text.

main
The main function. Reads arguments and calls respective functions.

AUTHOR

Steffen Schwigon <ss5 AT renormalist DOT net>

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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