[Twisted-Python] epoll reactor problems

Alec Matusis matusis at matusis.com
Wed Apr 11 03:51:49 EDT 2007

We just switched 2 types of production servers to epoll reactor( Twisted
2.5) from poll reactor (Twisted 2.2).

The CPU%% utilization of the first type of server that does not do much
except occasionally pushing messages to about 5000 clients dropped from
about 40% to 8%, which is very good.


The second type of server is more complicated. The CPU utilization of that
server (as measured by top) went down from 40% to about 15% after switching
to epoll.

Here is the problem: after about 10min of running that server with CPU%%
staying at about 15%, the CPU suddenly jumps to 99.9% for that process and
just stays there. We reproduced this several times. The server remains
responsive, even when top shows 99.9% CPU. (Which is very different from
99.9% CPU from real load when we used poll- we are intimately familiar with
the performance in that regime unfortunately.)

The kernel is


Can anybody help with this 99.9% CPU epoll problem?



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