Java periodically hangs at futex and very low IO output

Question

Currently my application periodically blocked in IO , and the output is very low . I use some command to trace the process.

By using jstack i found that the

Answer 1

In addition to clock jumps and aforementioned (rather old) THP kernel bug, another common reason for java to unexpectedly block on IO is reading very slow and blocking /dev/random which some libraries prefer over more commonly used and much better performing /dev/urandom.

Easy way to tell if that was the culprit:

sudo mv /dev/random /dev/random.real
sudo ln -s /dev/urandom /dev/random

...then restart the app and see if it stops IO blocking. Once done with the test, you probably want to restore /dev/random:

sudo mv /dev/random.real /dev/random

...and open a bug with application vendor asking to use /dev/urandom where appropriate.