Stress 0.18.1

Stress

• Overview: Overview of stress.
• Invoking stress: How to run stress.
• Examples: Some example invocations.
• Copying This Manual:
• Index:

Overview of stress

stress is not a benchmark, but is rather a tool designed to put given subsytems under a specified load. Instances in which this is useful include those in which a system administrator wishes to perform tuning activities, a kernel or libc programmer wishes to evaluate denial of service possibilities, etc.

Invoking stress

The format for running the stress program is:

     stress [option [args]] ...
     

stress supports the following options:

-?

--help

Show help information.

--version

Show version information.

-v

--verbose

Turn up verbosity.

-q

--quiet

Turn down verbosity.

-n

--dry-run

Show what would have been done.

-t secs

--timeout secs

Time out after secs seconds.

--backoff usecs

Wait for factor of usecs microseconds before starting work.

-c forks

--cpu forks

Spawn forks processes each spinning on sqrt().

-i forks

--io forks

Spawn forks processes each spinning on sync().

-m forks

--vm forks

Spawn forks processes each spinning on malloc().

--vm-bytes bytes

Allocate bytes number of bytes. The default is 1.

--vm-hang

Instruct each vm hog process to go to sleep after allocating memory. This contrasts with their normal behavior, which is to free the memory and reallocate ad infinitum. This is useful for simulating low memory conditions on a machine. For example, the following command allocates 256M of RAM and holds it until killed.

          % stress --vm 2 --vm-bytes 128M --vm-hang
          

-d forks

--hdd forks

Spawn forks processes each spinning on write().

--hdd-bytes bytes

Write bytes number of bytes. The default is 1GB.

--hdd-noclean

Do not unlink file(s) to which random ASCII data is written.

Note: Suffixes may be s,m,h,d,y (time) or k,m,g (size).

Example invocations

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, the default is to unlink it, but unlinking can be overridden with the -hdd-noclean flag.

% stress -d 1 --hdd-noclean --hdd-bytes 13

Large file support is enabled.

% stress -d 1 --hdd-noclean --hdd-bytes 3G

Copying This Manual

You may copy this manual under the terms of the GNU Free Documentation License.

Index

• invoking stress: Invoking stress
• stress: Invoking stress