DragonFly commits List (threaded) for 2005-05
Re: cvs commit: src/sys/i386/i386 trap.c src/sys/kern kern_poll.c
:On Wed, May 25, 2005 at 01:06:53AM -0700, Matthew Dillon wrote:
:> Putting a hook in the trap code does not result in any sort of
:> deterministic operation. I don't know who put that hack in there
:> (inherited from FreeBSDland) and I don't want to know. That whole mess
:> was put in because hardclock (the normal polling point) is a totally
:> inadequate place to trigger the poll.
:The reason it is there doesn't have anything to do with hardclock.
:It's cheap to check there and helps network programs by reducing
Cheap is a relative term. But you are missing the point... the problem
isn't whether it's cheap, it's whether it provides any sort of
deterministic, reliable operation. And the answer is: it doesn't.
Here's a thought experiment:
What is the overhead of taking 1000 interrupts per second on a
modern machine ? Just the overhead. What about 10,000 interrupts per
Now once you've calculated that, try to think up a good reason to do
the polling any other way.