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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] cpufreq implementation for OMAP under xen hypervisor.
On Wed, Sep 10, 2014 at 1:24 PM, Vitaly Chernooky <vitalii.chernookyi@xxxxxxxxxxxxxxx> wrote: > Hi Andrii, > > > On Wed, Sep 10, 2014 at 1:15 PM, Andrii Tseglytskyi > <andrii.tseglytskyi@xxxxxxxxxxxxxxx> wrote: >> >> Hi, >> >> >> In case where dom0 has more vcpus than pcpus on the >> >> system, the dom0 kernel is the most bug-prone place for pcpu cpufreq >> >> governor. So I still believe that separate driver >> >> domain with direct 1:1 vcpu:pcpu mapping is the best place for cpufreq >> >> governor. But it also reasonable to run cpufreq >> >> governor as userspace daemon in dom0. >> >> >> >> Also what do you think about PM QoS support? On bare metal cpufreq is >> >> tightly integrated with PM QoS and intensively >> >> cooperate in frequency scaling. >> > >> > Device PM needs to be done in Dom0. >> > CPU an Platform level PM architecturally belongs to Xen, but I do >> > understand that to do that in Xen we would need to add lots of code to >> > the hypervisor. There is no silver bullet here. >> > >> > A driver domain with 1:1 vcpu:pcpu mapping could work, but what kernel >> > are you going to use for that? Linux? Wouldn't Linux be too big for a >> > cpufreq driver domain, especially in embedded deployments? I think it >> > would need at least 32MB to run. >> > >> >> I would suggest not to do this. Driver domain will need to share the >> same HW with dom0, which is impossible to implement. Good examples are >> I2C, which is needed for Display and for Cpufreq, and it cannot be >> shared between domains. (At least in current Linux kernel it won't be >> easy to implement). dom0 is the best place to do cpufreq. > > > What do you think about cpufreq in dom0 userspace? > What do you mean? Could you please explain with more details? Regards, Andrii -- Andrii Tseglytskyi | Embedded Dev GlobalLogic www.globallogic.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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