Getting resource usage

Get resource usage: getrusage()

The function getrusage() returns resource usage statistics for the calling process, which is the sum of resources used by all threads in the process. The parameter $mode is optional. If you call getrusage() with no parameters it returns resource usage statistics for the calling process. If you call it with 1 value as a parameter, getrusage(1), (RUSAGE_CHILDREN) it returns resource usage statistics for all children of the calling process that have terminated and been waited for.

It returns an associative array with "resource name" => "value".

The resources are:

• ru_utime: user CPU time used, this is the total amount of time spent executing in user mode, expressed in a timeval structure, tv_sec (seconds) and tv_usec (microseconds);
• ru_stime: system CPU time used, the total amount of time spent executing in kernel mode, expressed in a timeval structure, tv_sec (seconds) and tv_usec (microseconds);
• ru_maxrss: maximum resident set size, the maximum resident set size used (in kilobytes), with $mode=1, is the resident set size of the largest child;
• ru_minflt: page reclaims (soft page faults), number of page faults serviced without any I/O activity;
• ru_majflt: page faults (hard page faults), number of page faults serviced that required I/O activity;
• ru_inblock: block input operations, number of times the file system had to perform input;
• ru_oublock: block output operations, number of times the file system had to perform output;
• ru_nvcsw: voluntary context switches, number of times a context switch resulted due to a process voluntarily giving up the processor before its time slice was completed (usually to await availability of a resource);
• ru_nivcsw: involuntary context switches, number of times a context switch resulted due to a higher priority process becoming runnable or because the current process exceeded its time slice.

$resources = getrusage();
foreach ($resources as $key => $value) {
    echo "=> " . $key . ": " . $value . PHP_EOL;
}
/*
The execution shows:
=> ru_oublock: 0
=> ru_inblock: 0
=> ru_msgsnd: 0
=> ru_msgrcv: 0
=> ru_maxrss: 12034048
=> ru_ixrss: 0
=> ru_idrss: 0
=> ru_minflt: 3151
=> ru_majflt: 0
=> ru_nsignals: 0
=> ru_nvcsw: 1
=> ru_nivcsw: 194
=> ru_nswap: 0
=> ru_utime.tv_usec: 26337
=> ru_utime.tv_sec: 0
=> ru_stime.tv_usec: 33557
=> ru_stime.tv_sec: 0
*/

The input parameter $mode

If you call getrusage() with 1 as input parameter, it is shown the resource usege of children processes. If you call getrusage(1) and the process doesn’t have any children, all values will be 0:

// $mode 1
$resources = getrusage(1);
foreach ($resources as $key => $value) {
    echo "=> " . $key . ": " . $value . PHP_EOL;
}

If you call getrusage(1) after having lanched a processes, you will see the resources used by the child process. In the example exec('sleep 1') it simulates the process creation.

// $mode 1 after executing an external process
exec('sleep 1');
$resources = getrusage(1);
foreach ($resources as $key => $value) {
    echo "=> " . $key . ": " . $value . PHP_EOL;
}