pyflame shows cpu is high idle, but nmon command shows cpu is full load.

[coder-zhuyu]

I run tornado with aiomysql on ubuntu 16.04, python version is 3.5.2.
I only execute a simple select db query on mysql.
pyflame shows cpu is high idle, but nmon command shows cpu is full load.
It's so strange?

[eklitzke]

Can you tell me what version of Pyflame you're using, and also what flags you're passing to Pyflame?

If the app is threaded, make sure you are using --threads with Pyflame.

You also might want to try running with -s 0 to see if you get a reasonable looking stack trace.

[coder-zhuyu]

pyflame 1.4.4, Compiled Jul 26 2017, 10:43:24 by GCC 5.4.0 20160609
The app is not threaded.
sudo pyflame -s 5 -r 0.001 -o prof.txt 6505
The flame picture is shown: https://coder-zhuyu.github.io/images/prof-tornado.svg

[eklitzke]

This looks pretty normal to me. You can use -x to exclude the idle times, but you probably already know that.

My guess is that if you use GDB to attach to the process, you will see that it's frequently blocking in the Tornado event loop. IIRC, you'll see a call to something like __epoll_wait() as frame 0 as reported by the GDB bt command. Try getting a backtrace from GDB a dozen times or so, and if Pyflame says your program is idle about 50% of the time then you should see the __epoll_wait() call about 50% of the time as well.

[coder-zhuyu]

I understand.
Thank you for your answer.