From: Chris Mason <chris.mason@...>
Date: 2010-11-11T02:34:53+09:00
Subject: [ruby-core:33127] Re: timer thread sleep interval (powertop abuses)

Excerpts from SASADA Koichi's message of 2010-11-10 12:13:56 -0500:
> Hi,
> 
> (2010/11/11 0:10), Chris Mason wrote:
> > powertop reports that ruby is triggering constant wakeups on linux,
> > which prevents us from doing proper power management.
> > 
> > I see a few ideas tossed around in the issue tracker, but it looks like
> > they are centered around preventing the timer thread when there is only
> > one thread.  We'll still want to cut down on wakeups even when there are
> > multiple threads.
> 
> Why do you want to reduce timer thread wake-up counts?  Power issues?

Correct, the wakeups prevent the CPU from going into lower
power modes.  It directly translates to more power usage and less time
on battery.  I found this while using sup, which is an email client that
we want to leave running for long periods.

> 
> (I want to know the pragmatic requirements)
> 
> > Is the timer thread required for the threads to function?  Or is it only
> > there to deliver signals etc?
> 
> The main purpose of the timer thread is thread switching notification.

So, if I set the sleep to 500ms, then I'll only switch threads every
500ms?  That's probably not ideal ;)

-chris