Using the runlim Command (with examples)
- Linux
- November 5, 2023
The runlim command is a useful tool for sampling and limiting the time and memory usage of a program, along with its child processes, on a Linux system. In this article, we will explore different use cases of the runlim command, along with code examples and their respective outputs.
Print the time and memory usage of a command
To print the time and memory usage of a specific command, you can use the following code:
runlim command command_arguments
Motivation: This use case is helpful when you want to analyze the time and memory consumption of a command. By using runlim, you can get an overview of how a program utilizes system resources.
Explanation:
command: The command you want to execute.command_arguments: Any optional arguments required by the command.
Example Output:
Time Limit : 69.40s
Memory Limit: Unlimited
Command: ls -l
...
Log statistics to a file instead of stdout
To log the statistics of a command to a file instead of printing them to the standard output (stdout), you can use the following code:
runlim --output-file=path/to/file command command_arguments
Motivation: Logging statistics to a file can be advantageous when you want to analyze the data later or store it for future reference. This allows for easy comparison or sharing of results.
Explanation:
path/to/file: The path to the file where you want to log the statistics.command: The command you want to execute.command_arguments: Any optional arguments required by the command.
Example Output:
The statistics of the command are logged into the specified file.
Limit time to an upper bound (in seconds)
To limit the execution time of a command to an upper bound in seconds, you can use the following code:
runlim --time-limit=number command command_arguments
Motivation: Sometimes, you may want to restrict the execution time of a command to prevent resource exhaustion or ensure fair resource allocation. By setting a time limit, you can mitigate the risks associated with long-running commands.
Explanation:
number: The maximum allowed time in seconds.command: The command you want to execute.command_arguments: Any optional arguments required by the command.
Example Output:
Time Limit : 5s
Memory Limit: Unlimited
Command: python script.py
Execution terminated due to time limit exceeded.
Limit real-time to an upper bound (in seconds)
To limit the real-time (wall-clock time) of a command to an upper bound in seconds, you can use the following code:
runlim --real-time-limit=number command command_arguments
Motivation: Unlike the previous use case, limiting real-time takes into account the total time spent in both user and kernel modes, including waiting for I/O operations. This can be beneficial when dealing with time-sensitive tasks or preventing excessive system idle time due to long-running commands.
Explanation:
number: The maximum allowed real-time in seconds.command: The command you want to execute.command_arguments: Any optional arguments required by the command.
Example Output:
Time Limit : 10s
Memory Limit: Unlimited
Command: ./run_simulation
Execution terminated due to real-time limit exceeded.
Limit space to an upper bound (in MB)
To limit the memory space used by a command to an upper bound in megabytes (MB), you can use the following code:
runlim --space-limit=number command command_arguments
Motivation: Memory constraints are often crucial in resource-constrained environments. Setting a space limit can prevent memory-intensive commands from exhausting system memory and causing out-of-memory errors.
Explanation:
number: The maximum allowed memory space in megabytes.command: The command you want to execute.command_arguments: Any optional arguments required by the command.
Example Output:
Time Limit : Unlimited
Memory Limit: 256MB
Command: java -Xmx256m MyApp
...
We have explored five different use cases of the runlim command, highlighting scenarios where each use case can be beneficial. In the next section, we will cover three more use cases.
Use Case 6
Command: runlim --help
Motivation: To display the help information for the runlim command, including the available options and their usage.
Explanation: By executing runlim with the --help option, you can obtain concise information on the command’s usage, making it easier to understand and utilize its features.
Example Output:
Usage: runlim [options] command arguments...
A tool for sampling and limiting time and memory usage of a program and its child processes using the proc file system on Linux.
Options:
-l, --time-limit Limit the CPU time [default: unlimited]
-r, --real-time-limit Limit the real-time [default: unlimited]
-m, --space-limit Limit the space usage [default: unlimited]
-o, --output-file Write statistics to a file
-h, --help Print this help message and exit
More information: <http://fmv.jku.at/runlim>.
Use Case 7
Command: runlim --version
Motivation: To retrieve the version information of the runlim command currently installed on the system.
Explanation: Running runlim with the --version option allows you to quickly determine the installed version of the command, which can be useful for troubleshooting or ensuring compatibility with other tools.
Example Output:
runlim 1.17
Use Case 8
Command: runlim --space-limit=512
Motivation: To limit the memory space used by a command to 512 megabytes (MB).
Explanation: In this use case, we set the space limit to 512 MB by passing the --space-limit option followed by the desired memory size. This ensures that the command will not exceed the specified memory consumption, preventing system instability or performance degradation.
Example Output:
Time Limit : Unlimited
Memory Limit: 512MB
Command: ./process_data
...
In conclusion, the runlim command is a versatile tool for sampling and limiting the time and memory usage of programs on a Linux system. By understanding its various use cases, you can effectively monitor and control resource utilization, provide fair resource allocation, and prevent system instability.
