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Role: Documentation
Content type: text/plain
Description: Documentation
Class: CPU Load Calculator
Retrieve the CPU load level under Linux
Author: By
Last change:
Date: 18 years ago
Size: 3,165 bytes


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class_CPULoad.php - CPU Load Class Copyright 2001-2002, Steve Blinch (BlitzAffe Online, Latest version available at: Contact: DESCRIPTION This script obtains CPU load percentage information from /proc/stat, allowing the server to display User, Nice, System, Idle, and CPU load percentages to users. USAGE The most important concept to note when using the CPULoad class is that the CPU load can only be calculated over a period of time. For example, the script needs to check the current CPU load, wait for a second or two, then check the CPU load again to get an accurate reading. There are two ways to do this: 1. When the script is called, it can pause for one or two seconds to get an accurate reading. While this works, it tends to be cumbersome on busier sites, since the page takes one or two seconds longer to load. 2. The script can save the CPU data to a file every time it runs, then refer back to it the next time it is executed. This requires no delay in processing. The only drawback is that the CPU load is calculated over the time period between page loads. For example, if the page hasn't been visited for an hour, the next visitor will see the CPU load average for the last hour (rather than the current CPU load). Generally number 2 is the best method. The most commonly used functions of the CPULoad class are: CPULoad::sample_load($interval=1) This function corresponds to method number 1 above. The CPULoad class checks the CPU load, waits for 1 second, then re-checks the CPU load. It then calculates the CPU load over that 1 second period. If you pass a value for $interval, this specifies the number of seconds to wait between checks. Higher values make for more accurate readings, but will delay your script's execution. CPULoad::get_load($fastest_sample=4) This function corresponds to method number 2 above. The CPULoad class saves a small file in /tmp/ every time it is called, and uses it to remember the CPU load information. It then calculates the average CPU load since the last time it was called. If you pass a value for $fastest_interval, this specifies the minimum number of seconds (between page loads) that must elapse before the CPU load is recalculated. Generally, 4 is good for accurate values. CPULoad::print_load() This function outputs the calculated CPU load information. If you want access to the raw CPU load percentage information, the following variables are available: CPULoad->load["user"] - contains the User Mode load percentage CPULoad->load["nice"] - contains the Low Priority User Mode load percentage CPULoad->load["system"] - contains the System Mode load percentage CPULoad->load["idle"] - contains the Idle load percentage CPULoad->load["cpu"] - contains overall CPU load CPULoad->cached - contains the number of seconds remaining until the CPU load is recalculated (if using CPULoad::get_load()). If these descriptions sound confusing, just try out the sample script included; it's really simple to use.