[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] xhci_hcd intterrupt affinity in Dom0/DomU limited to single interrupt
On Thu, 2015-09-03 at 09:04 -0600, Jan Beulich wrote: > >>> On 03.09.15 at 14:04, <ackerj67@xxxxxxxxx> wrote: > >>>> On 02.09.15 at 19:17, <ackerj67@xxxxxxxxx> wrote: > >> From: Jan Beulich <jbeulich@xxxxxxxx> > >> Sent: Wednesday, September 2, 2015 4:58 AM > >>>>> Justin Acker <ackerj67@xxxxxxxxx> 09/02/15 1:14 AM >>> > >>> 00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset > > Family USB xHCI Host Controller (rev 04) (prog-if 30 [XHCI]) > >>> Subsystem: Dell Device 053e > >>> Flags: bus master, medium devsel, latency 0, IRQ 78 > >>> Memory at f7f20000 (64-bit, non-prefetchable) [size=64K] > >>> Capabilities: [70] Power Management version 2 > >>> Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+ > >> > >> This shows that the driver could use up to 8 MSI IRQs, but chose to use > >> just > > > >> one. If > >> this is the same under Xen and the native kernel, the driver likely > >> doesn't > >> know any > >> better. If under native more interrupts are being used, there might be an > >> issue with > >> Xen specific code in the kernel or hypervisor code. We'd need to see > >> details > > > >> to be > >> able to tell. > >> > >> Please let me know what details I should provide. > > I'd like to emphasize what I said in my previous reply: Apologies. The Webmail client doesn't support in-line replies or I couldn't figure out how to turn these on. Hopefully this is better. > > > Please, first of all, get your reply style fixed. Just look at the above > > and tell me how a reader should figure which parts of the text were > > written by whom. > > > >[...] > > > > I am still confused as to whether any device, or in this case > > xhci_hcd, > > can use more than one cpu at any given time. My understanding based on > > David's response is that it cannot due to the event channel mapping. The > > device interrupt can be pinned to a specific cpu by specifying the > > affinity. I was hoping there was a way to allow the driver's interrupt to > > be > > scheduled to use more than 1 CPU at any given time. > > The problem is that you're mixing up two things: devices and > interrupts. Any individual interrupt can only be serviced by a single > CPU at a time, due to the way event channels get bound. Any > individual device can have more than one interrupt (MSI or MSI-X), > and then each of these interrupts can be serviced on different > CPUs. > > Jan > Thanks for clarifying. To the original question, with respect to my limited understanding of the event channels and interrupts, each interrupt can be serviced on a different CPU using irqbalance or setting the affinity manually, but the same interrupt cannot be serviced by more than 1 CPU at a time? If so, is there a way around the 1:1 binding when loading the Dom0 kernel - a flag or option to use the native interrupt scheduling for some set of or all 8 CPUs that the device can schedule interrupts on when not loading the Dom0? The xhci_hcd, as one example, seems to perform better when it is able to have interrupts serviced by multiple CPUs. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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