[Twisted-Python] Re: epoll reactor problems

Alec Matusis matusis at matusis.com
Wed Apr 11 04:15:08 EDT 2007

PS. One more piece of data: we just switched that server back to poll, still
on Twisted 2.5. The CPU is at 30-45% stable, with exactly the same usage. So
this is either caused by the epoll() itself, or by the epoll reactor in

From: Alec Matusis [mailto:matusis at matusis.com] 
Sent: Wednesday, April 11, 2007 12:52 AM
To: 'Twisted general discussion'
Subject: epoll reactor problems

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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