This is a good find. In my humble opinion -- and since a lot of applications are moving to virtualised guests -- a low-resolution timer should be used by default. It would then be the call of the developer to explicitly decide otherwise.
This is a genuine case of use worst case by default with the end user specifically specifying more granularity. The VirtualBox ticket was closed as invalid, and it was suggested that this is a Microsoft "issue". Is this something that should be changed by default only on Microsoft builds? Felipe, is this something you could try and reproduce with a Linux guest? -- Justin Cook On Tuesday, 15 October 2013 at 19:49, Felipe Farinon wrote: > That seems a strange thing to do, since even Windows doesn't guarantee > the monotonicity of the timer used by QPC (e.g. when using ACPI timer). > If we want to cover the cases where Windows is using ACPI timer, even > outside of VirtualBox, we should make it possible to switch by default > to GetTickCount64. Note that if the ZeroMQ user doesn't use a small > timeout in zmq_poll, this shouldn't be a big penalty. > > By the way, detecting that we're running inside a virtual machine is a > rather difficult process. Most techniques may lead to false positives. > > Em 15/10/2013 15:26, Pieter Hintjens escreveu: > > Is there any way to detect at runtime that we're running in VirtualBox? > > > > On Tue, Oct 15, 2013 at 7:48 PM, Felipe Farinon > > <felipe.fari...@powersyslab.com (mailto:felipe.fari...@powersyslab.com)> > > wrote: > > > I´ve built an application that is running on a Windows 7 inside a > > > VirtualBox, with zeromq 3.2.2. > > > > > > == The problem == > > > When running one test, I noticed that my application called zmq_poll > > > with timeout of 2000 but it at one day stopped expiring the timeout. > > > Similarly, a client application that connected to it and had a loop that > > > used QueryPerformanceCounter for timeout, suddenly froze and stopped > > > firing the timeout. After doing some research, I have found that > > > VirtualBox's QueryPerformanceCounter doesn't guarantee monotonicity > > > https://www.virtualbox.org/ticket/11951. They argue that even Windows > > > QueryPerformanceCounter doesn't guarantee it. > > > > > > Then I have found that zmq_poll calls clock_t::now_ms which in turn > > > calls clock_t::now_us which uses QueryPerformanceCounter. > > > > > > == My proposal == > > > We could add a zeromq define that makes zmq_poll use a low precision > > > timer, such as GetTickCount64 which has less bugs. > > > _______________________________________________ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
