Improve CPU usage efficiency

[provrb]

Problem

The compute_cpu_usage function relied on redundant operations and inefficient handling of cached system times. This could lead to unnecessary updates to system times, resulting in reduced efficiency and increased overhead.

Solution

I updated the function to use cached values unless the time elapsed since the previous values were cached exceeds MINIMUM_CPU_UPDATE_INTERVAL, ensuring system times are only refreshed when necessary.

• Specifically minimizes the amount of calls to GetSystemTimes, and filetime_to_u64.

Now, after each call to compute_cpu_usage if the last time these values were retrieved ( a call to GetSystemTimes took place ) is less than MINIMUM_CPU_UPDATE_INTERVAL ( system values haven't updated ) the function will use the values used previously. Otherwise, GetSystemTimes will be called, values will be retrieved, and an Instant::now() value will be saved in cpu_calc_values to determine the time GetSystemTimes was last called.

Tests

• All 237 existing tests passed and ran with cargo test.

Other

• Both cargo fmt and cargo clippy were ran successfully.

[GuillaumeGomez]

At this point, why not just return the previously computed cpu usage?

[provrb]

I apologize for my significant oversight. I revised the code to return the unchanged process CPU usage if the last_update field hasn't exceeded the time it takes to update the CPU values. It should be good now. Again, passed all cargo fmt, clippy and test commands.