CODEWITHSUNDEEP
pythonpsutil
Chris
Chris

Reputation: 1027

How to get accurate process CPU and memory usage with python?

I am trying to create a process monitor but I am unable to get accurate results comparing my results to windows task manager.

I have been using psutil which seems to work fine when looking at the overall cpu and memory usage but doesn't appear to be very accurate for a single process. Memory usage is always higher than task manager and CPU it always random.

I am setting the process once on initialise with self.process = psutil.Process(self.pid) and then calling the below method once a second, the process in task manager is running at a constant 5.4% cpu usage and 130mb ram however the below code produces:

CPU: 12.5375
Memory 156459008
CPU: 0.0
Memory 156459008
CPU: 0.0
Memory 156459008
CPU: 0.0
Memory 156459008
CPU: 12.5375
Memory 156459008
CPU: 0.0
Memory 156459008
CPU: 0.0
Memory 156459008

Example code:

def process_info(self):    
        # I am calling this method twice because I read the first time gets ignored?
        ignore_cpu = self.process.cpu_percent(interval=None) / psutil.cpu_count()
        time.sleep(0.1)
        process_cpu = self.process.cpu_percent(interval=None) / psutil.cpu_count()
        
        # I also tried the below code but it was much worse than above
        # for j in range(10):
        #     if j == 0:
        #         test_list = []
        #     p_cpu = self.process.cpu_percent(interval=0.1) / psutil.cpu_count()
        #     test_list.append(p_cpu)
        # process_cpu = (sum(test_list)) / len(test_list)

        # Memory is about 25mb higher than task manager
        process_memory = self.process.memory_info().rss

        print(f"CPU: {process_cpu}")
        print(f"Memory: {process_memory}")

am I using psutil incorrectly or is there a more accurate way to grab the data?

Upvotes: 16

Views: 10101

Answers (3)

James
James

Reputation: 180

I think you are misinterpreting the output of psutil.cpu_percent(). Returns a float representing the current system-wide CPU utilization as a percentage. When interval is > 0.0 compares process times to system CPU times elapsed before and after the interval (blocking). When interval is 0.0 or None compares process times to system CPU times elapsed since last call, returning immediately. That means that the first time this is called it will return a meaningful 0.0 value on which subsequent calls can be based. In this case is recommended for accuracy that this function be called with at least 0.1 seconds between calls.

So, if you call it with interval=0.1, it will return the percentage of time the process was running in the last 0.1 seconds. If you call it with interval=None, it will return the percentage of time the process was running since the last time you called it. So, if you call it twice in a row with interval=None, the first call will return the percentage of time the process was running since the last time you called it, and the second call will return the percentage of time the process was running since the last time you called it. So, if you want to get the percentage of time the process was running in the last 0.1 seconds, you should call it with interval=0.1.

Upvotes: 9

ShadowProgrammer
ShadowProgrammer

Reputation: 82

Like @Axeltherabbit mentioned in his comment, Task Manager grabs all processes under a given name, whereas psutils grabs an individual process. psutils is correct, task manager over-scopes and decides to grab all processes.

Upvotes: 1

Wael Jlassi
Wael Jlassi

Reputation: 133

this should be more accurate i think?

    import psutil

for process in [psutil.Process(pid) for pid in psutil.pids()]:
    try:
        process_name = process.name()
        process_mem = process.memory_percent()
        process_cpu = process.cpu_percent(interval=0.5)
    except psutil.NoSuchProcess as e:
        print(e.pid, "killed before analysis")
    else:
        print("Name:", process_name)
        print("CPU%:", process_cpu)
        print("MEM%:", process_mem)

Upvotes: 0

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