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Re: process wakeups
- From: "Daniel P. Berrange" <berrange redhat com>
- To: Ulrich Drepper <drepper redhat com>
- Cc: Development discussions related to Fedora <fedora-devel-list redhat com>
- Subject: Re: process wakeups
- Date: Tue, 15 Jul 2008 20:13:15 +0100
On Tue, Jul 15, 2008 at 10:22:09AM -0700, Ulrich Drepper wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Daniel P. Berrange wrote:
> >> uid | poll select epoll itimer futex nanosle signal| process
> >> 2397 | 16 0 0 0 0 0 0| libvirtd
> >
> > This isn't libvirtd's fault - we don't use any timeouts, and only
> > break out of poll() if there's real work todo.
>
> The script counts returns from poll() where no file descriptor is ready.
> This is no count of all poll() calls.
Sorry I wasn't being clear. The call to poll() with a 0 second timeout
is an artifact of the way the DBus/Avahi/event loop integration works.
It gets a wakeup on a file descriptor, processes some messages and then
does one iteration through the main loop with a 0 second timeout to
flush out the queues, before finally going back to sleep for events on
its file descriptors. As such the poll() with timeout is harmless - the
process was already awake at this point. Its the wakeup from irrelevant
DBus signals that's the real problem that needs to be addressed - once
that's solved the poll() will timeout won't be done.
Daniel
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