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stress - tool to impose load on and stress test a computer system


stress [OPTIONS]


stress is a tool that imposes a configurable amount of CPU, memory, I/O, or disk stress on a POSIX-compliant operating system and reports any errors it detects.

stress is not a benchmark. It is a tool used by system administrators to evaluate how well their systems will scale, by kernel programmers to evaluate perceived performance characteristics, and by systems programmers to expose the classes of bugs which only or more frequently manifest themselves when the system is under heavy load.


-?, --help

Show this help statement.


Show version statement.

-v, --verbose

Be verbose.

-q, --quiet

Be quiet.

-n, --dry-run

Show what would have been done.

-t, --timeout <N>

Timeout after N seconds. This option is ignored by -n.

--backoff <N>

Wait for factor of microseconds before starting work.

-c, --cpu <N>

Spawn N workers spinning on sqrt().

-i, --io <N>

Spawn N workers spinning on sync().

-m, --vm <N>

Spawn N workers spinning on malloc()/free().

--vm-bytes <B>

Malloc B bytes per vm worker (default is 256MB).

--vm-stride <B>

Touch a byte every B bytes (default is 4096).

--vm-hang <N>

Sleep N secs before free (default none, 0 is inf).


Redirty memory instead of freeing and reallocating.

-d, --hdd <N>

Spawn N workers spinning on write()/unlink().

--hdd-bytes <B>

Write B bytes per hdd worker (default is 1GB). The file will be created with mkstemp() in the current directory.

Note: Numbers may be suffixed with s,m,h,d,y (time) or B,K,M,G (size).


The simple case is that you just want to bring the system load average up to an arbitrary value. The following forks 13 processes, each of which spins in a tight loop calculating the sqrt() of a random number acquired with rand().

stress -c 13

Long options are supported, as well as is making the output less verbose. The following forks 1024 processes, and only reports error messages if any.

stress --quiet --cpu 1k

To see how your system performs when it is I/O bound, use the -i switch. The following forks 4 processes, each of which spins in a tight loop calling sync(), which is a system call that flushes memory buffers to disk.

stress -i 4

Multiple hogs may be combined on the same command line. The following does everything the preceding examples did in one command, but also turns up the verbosity level as well as showing how to cause the command to self-terminate after 1 minute.

stress -c 13 -i 4 --verbose --timeout 1m

You can write a file of arbitrary length to disk. The file is created with mkstemp() in the current directory.

stress -d 1 --hdd-bytes 13

Large file support is enabled.

stress -d 1 --hdd-bytes 3G


stress was originally developed by Amos Waterland <apw@debian.org> and is maintained by some volunteers.

Currently, source code and newer versions are available at https://github.com/resurrecting-open-source-projects/stress