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From: | Alex Bligh |
Subject: | Re: [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff |
Date: | Wed, 24 Jul 2013 08:31:07 +0100 |
--On 24 July 2013 08:42:26 +0200 Paolo Bonzini <address@hidden> 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
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