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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Question about running a program(Intel PCM) in ring 0 on Xen
On lun, 2014-02-17 at 17:32 -0500, Meng Xu wrote: > Hi, > Hi, > I'm a PhD student, working on real time system. > Cool. There really seems to be a lot of interest in Real-Time virtualization these days. :-D > [My goal] > I want to measure the cache hit/miss rate of each guest domain in Xen. > I may also want to measure some other events, say memory access rate, > for each program in each guest domain in Xen. > Ok. Can I, out of curiosity, as you to detail a bit more what your *final* goal is (I mean, you're interested in these measurements for a reason, not just for the sake of having them, right?). > [The problem I'm encountering] > I tried intel's Performance Counter Monitor (PCM) in Linux on bare > machine to get the machine's cache access rate for each level of > cache, it works very well. > > > However, when I want to use the PCM in Xen and run it in dom0, it > cannot work. I think the PCM needs to run in ring 0 to read/write the > MSR. Because dom0 is running in ring 1, so PCM running in dom0 cannot > work. > Indeed. > So my question is: > How can I run a program (say PCM) in ring 0 on Xen? > Running "a program" in there is going to be terribly difficult. What I think you're better off is trying to access, from dom0 and/or (para)virtualize the counters. In fact, there is work going on already on this, although I don't have all the details about what's the current status. > What's in my mind is: > Writing a hypercall to call the PCM in Xen's kernel space, then the > PCM will run in ring 0? > But the problem I'm concerned is that some of the PCM's instruction, > say printf(), may not be able to run in kernel space? > Well, Xen can print, e.g., on a serial console, but again, that's not what you want. I'm adding the link to a few conversation about virtual PMU. These are just the very first google's result, so there may well be more: http://xen.1045712.n5.nabble.com/Virtualization-of-the-CPU-Performance-Monitoring-Unit-td5623065.html https://lwn.net/Articles/566159/ Boris (which I'm Cc-ing), gave a presentation about this at latest Xen Developers Summit: http://www.slideshare.net/xen_com_mgr/xen-pmu-xensummit2013 Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) Attachment:
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