Re: [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff

[Alex Bligh <alex@alex.org.uk>]

--On 24 July 2013 08:42:26 +0200 Paolo Bonzini <pbonzini@redhat.com> wrote:

> With ppoll, is this true or just hearsay?
>
> (Without ppoll, indeed setitimer has 1 us resolution while poll has 1
> ms; too bad that select has other problems, because select has also 1 us
> resolution).

Most 'reasonable' POSIX compliant operating systems have ppoll and I would
have thought there is /better/ resolution there than relying not only
on signal, but also a pipe or eventfd plus the underlying poll().

If it was my comments you are referring to, my concern was mainly about
Windows (which I know very little about), as there does not appear
to be a nanosecond or even microsecond alternative to
WaitForMultipleObjects. However, articles like this:

 
http://social.msdn.microsoft.com/Forums/vstudio/en-US/e8a7cb1e-9edd-4ee3-982e-f66b7bf6ae44/improve-accuracy-waitforsingleobject

suggest that WaitFor{Single,Multiple}Objects can have pretty
appalling latency anyway (100ms!), and there's no evidence that's
limited by making one of the FDs (or objects) ready. In these
circumstances, I'd question whether we gain anything by worrying
about timer resolution.

-- 
Alex Bligh