Hi Vic, Thanks for the update. We're glad to hear you sorted out the delays and that the cause was not VirtualBox :)
Also good to hear that there is a noticeable improvement with the latest code. We know it's faster (because guests perform better) but did not specifically measure the latency the way you did. Regards, Michal ----- Original Message ----- From: llyzs....@gmail.com To: michal.neca...@oracle.com, vbox-dev@virtualbox.org Sent: Wednesday, June 15, 2016 3:52:21 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna Subject: Re: [vbox-dev] Driver ISR call delayed for device interrupts 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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