On 07/19/2011 09:30 AM, Daniel P. Berrange wrote:
I'm wondering if the problem here is that libvirt is trying to use the pipe-to-self mechanism as a fundamental event loop idiom. That is, the reason libvirt is calling poll is in order to minimize CPU until something interesting happens, where interesting includes needing to wake up a helper thread to do an action inside locks in response to the receipt of a signal.
Maybe you are on to something, and replacing all uses of pipe() with virPipeToSelf() (which uses pipe() for efficiency on Linux, but socketpair() on mingw), would allow libvirt to continue to use the pipe-to-self idiom while also using fds that can actually be poll'd on mingw.
IIRC, we never resolved this for the last release. I think we should do as you suggest and just use socketpair() on Win32. Given the way in which libvirt uses these capabilities, I don't think the overheads of socketpair() vs pipe() are so onerous that we need worry about an even more fancy Win32 impl or eventfd for linux. Of course if someone wants todo a full job for gnulib meawhile, we won't complain...
Well, right now, we don't even have socketpair() for Win32. We'd have to wire up some other native APIs for this to work. -- Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org