Hi Michal & Ram, Thanks for you prompt response, in fact it has been very helpful.
You were right that the suspicious delay at every 500ms was not in VirtualBox. I have identified that this was something else I was running on the host that caused it, so sorry for the confusion. I am on stable 5.0 source. The way I measure the interrupt is to record the timestamp (QueryPerformanceCounter) when I call PDMDevHlpPCISetIrq to raise the interrupt level, and another timestamp when the driver sends another I/O to lower the interrupt in driver's ISR, then compare the two, so I think this should be precise. And I log the ones that only exceed 1ms. So after I fixed my own problem, the ISR delay is now mostly below 10ms, which is acceptable for me. I am certainly not expecting real-time response from a VM. :) For completeness, I also tried with the latest 5.1 source from SVN. And you were right again that there was noticeable improvement there. The delay is not 100% eliminated (of course) but it happens much less frequent and the delay tends to be much shorter, mostly 1-3ms. Thanks again. Vic On Wed, Jun 15, 2016 at 3:50 PM Michal Necasek <michal.neca...@oracle.com> wrote: > > Hi Vic, > > It probably does not hurt to state that if you require real-time > responsiveness, you should *not* be using a VM. There are no latency > guarantees. > > You forgot to mention the most relevant fact... which svn revision of > the OSE source code are you actually using? In fact you expect any kind > of technical support, you might as well start by providing a VBox.log > because all the information is in there. > > How exactly do you measure the delay? I assume it's from the device > calling PDMDevHlpPCISetIrq to the guest accessing some device register > in the ISR? > > There might be problems specific to Windows 8.1(?) hosts. If you could > repeat the test on a different host OS (ideally not Windows), that might > provide some hints. > > I don't know of anything in particular that would happen every 500 ms > in VirtualBox, but it doesn't have to be the VM, it could be the host > doing something as well. > > > Regards, > Michal > > > On 6/15/2016 8:51 AM, llyzs wrote: > > Hi Devs, > > > > I have a virtual PCI device added on VirtualBox OSE and a driver which > > sends I/O to do some stuff in the host and receive interrupts when the > > work is done. The interrupts work most of the time, however there are > > random delays between PDMDevHlpPCISetIrq is called and the driver ISR is > > called. Most of the time there is no delay (<1ms) but periodically there > > is a delay from 10+ms to even 60+ms. One more strange thing is that the > > delay mostly happen at exactly every 500ms. So anyone can give me some > > hint on what is causing the interrupt delay? What kind of job inside > > VirtualBox that runs every 500ms that might be causing interrupt delay? > > > > I am on Windows 8.1 x64 (both guest and host). Thanks in advanced. > > > > Vic > > > > > > _______________________________________________ > > vbox-dev mailing list > > vbox-dev@virtualbox.org > > https://www.virtualbox.org/mailman/listinfo/vbox-dev > > > > _______________________________________________ > vbox-dev mailing list > vbox-dev@virtualbox.org > https://www.virtualbox.org/mailman/listinfo/vbox-dev >
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