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Monitoring GPU usage with StackDriver

At work we use Google Cloud Platform to run our machine learning jobs on multiple machines. GCP has a monitoring platform called Stack­driv­er which can be used to view all kinds of metrics about your VMs. Un­for­tu­nate­ly, it doesn't collect any metrics about GPUs, neither usage or memory. The good news is that it is extensible and you can "easily" set up a new kind of metric and monitor it.

To get GPU metrics, we can use the nvidia-smi program, which is installed when you get all the necessary drivers for your graphics card. If you call it simply, it will give you the following output:

> nvidia-smi
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 410.66       Driver Version: 410.66       CUDA Version: 10.0     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  GeForce GTX 108...  Off  | 00000000:01:00.0  On |                  N/A |
|  0%   43C    P8    17W / 250W |   1309MiB / 11177MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+

+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|    0       700      G   /usr/lib/Xorg                                 40MiB |
|    0       733      G   /usr/bin/gnome-shell                         110MiB |
|    0       931      G   /usr/lib/Xorg                                371MiB |
|    0      1119      G   /usr/lib/firefox/firefox                       2MiB |
|    0      1279      G   /usr/lib/firefox/firefox                       3MiB |
|    0     23585      G   /usr/lib/firefox/firefox                      24MiB |
+-----------------------------------------------------------------------------+

This is a bit convoluted, hard to parse and has too many details. But, with the right flags, you can get just what you want in CSV format:

> nvidia-smi --query-gpu=utilization.gpu,utilization.memory --format=csv,noheader,nounits
10,35

The first value is the GPU uti­liza­tion, as a percentage, and the second value is the memory usage of the GPU, also as a percentage.

We are going to write a Python process that open a subprocess to call nvidia-smi once a second and aggregates statistics, on a per minute basis. We have to do this, because we cannot write to Stack­driv­er metrics more than once a minute, per label (which are a sort of identifier for these time series).

from subprocess import Popen, PIPE
import os
import time
import sys

def compute_stats():
    all_gpu = []
    all_mem = []
    for i in range(10):
        p = Popen(["nvidia-smi","--query-gpu=utilization.gpu,utilization.memory", 
                   "--format=csv,noheader,nounits"], stdout=PIPE)
        stdout, stderror = p.communicate()
        output = stdout.decode('UTF-8')
        # Split on line break
        lines = output.split(os.linesep)
        numDevices = len(lines)-1
        gpu = []
        mem = []
        for g in range(numDevices):
            line = lines[g]
            vals = line.split(', ')
            gpu.append(float(vals[0]))
            mem.append(float(vals[1]))

        all_gpu.append(gpu)
        all_mem.append(mem)
        time.sleep(1)

    max_gpu = [max(x[i] for x in all_gpu) for i in range(numDevices)]
    avg_gpu = [sum(x[i] for x in all_gpu)/len(all_gpu) for i in range(numDevices)]
    max_mem = [max(x[i] for x in all_mem) for i in range(numDevices)]
    avg_mem = [sum(x[i] for x in all_mem)/len(all_mem) for i in range(numDevices)]
    return max_gpu, avg_gpu, max_mem, avg_mem

Here we computed both the average and the maximum over a 1 minute interval. This can be changed to other statistics if they are more relevant for your use case.

To write the data to Stack­driv­er, we have to build up the ap­pro­pri­ate protobufs. We will set two labels: one for the zone in which are machines are and one for the instance_id, which we will hack to contain both the name of the machine and the number of the GPU (this is useful in case you attach multiple GPUs to one machine). I hacked the instance_id because Stack­driv­er kept refusing any API calls with custom labels, even though the docs said it supported them.

from google.cloud import monitoring_v3

client = monitoring_v3.MetricServiceClient()
project = 'myGCPprojectid'  
project_name = client.project_path(project)


def write_time_series(name, gpu_nr, value):
    series = monitoring_v3.types.TimeSeries()
    series.metric.type = 'custom.googleapis.com/' + name
    series.resource.type = 'gce_instance'
    series.resource.labels['instance_id'] = sys.argv[1] + "_gpu_" + str(gpu_nr)
    series.resource.labels['zone'] = 'us-central1-f'

    point = series.points.add()
    point.value.double_value = value
    now = time.time()
    point.interval.end_time.seconds = int(now)
    point.interval.end_time.nanos = int(
    (now - point.interval.end_time.seconds) * 10**9)
    client.create_time_series(project_name, [series])

And now, we put everything together. The program must be called with a the name of the instance as a first parameter. If you run it only on GCP, you can use the GCP APIs to get the name of the instance au­to­mat­i­cal­ly.

if len(sys.argv) < 2:
    print("You need to pass the instance name as first argument")
    sys.exit(1)

try:
    max_gpu, avg_gpu, max_mem, avg_mem = compute_stats()
    for i in range(len(max_gpu)):
        write_time_series('max_gpu_utilization', i, max_gpu[i])
        write_time_series('max_gpu_memory', i, max_mem[i])
        write_time_series('avg_gpu_utilization', i, avg_gpu[i])
        write_time_series('avg_gpu_memory', i, avg_mem[i])
except Exception as e:
    print(e)

If you save all this code to a file called gpu_monitoring.py and you run this locally, on a machine with an NVidia GPU, after a minute you should start seeing the new metrics in your Stack­driv­er console associated with your GCP project.

Stackdriver GPU graphs

This code can then be called with cron once a minute or it can be changed so that it runs without stopping, posting results once a minute.

* * * * * python /path/to/gpu_monitoring.py instance_name >> /var/log/gpu.log 2>&1

Setting up the GCP project and au­then­ti­ca­tion to connect to Stack­driv­er is left as an exercise to the user. The whole code can be seen in this gist.