On 8/29/19 10:51 PM, Daniel Lezcano wrote: > On 29/08/2019 23:12, Joao Martins wrote: > > [ ... ] > >>>> Say you wanted to have a kvm specific config, you would still see the same >>>> problem if you happen to compile intel_idle together with haltpoll >>>> driver+governor. >>> >>> Can a guest work with an intel_idle driver? >>> >> Yes. >> >> If you use Qemu you would add '-overcommit cpu-pm=on' to try it out. ofc, >> assuming you're on a relatively recent Qemu (v3.0+) and a fairly recent kernel >> version as host (v4.17+). > > Ok, thanks for the clarification. > >>>> Creating two separate configs here, with and without haltpoll >>>> for VMs doesn't sound effective for distros. >>> >>> Agree >>> >>>> Perhaps decreasing the rating of >>>> haltpoll governor, but while a short term fix it wouldn't give much sensible >>>> defaults without the one-off runtime switch. > > The rating has little meaning because each governor fits a specific > situation (server, desktop, etc...) and it would probably make sense to > remove it and add a default governor in the config file like the cpufreq. > ICYM, I had attached a patch in the first message of this thread [0] right below the scissors mark. It's not based on config file, but it's the same thing you're saying (IIUC) but at runtime and thus allowing a driver to state a 'preferred' governor to switch to at idle registration -- let me know if you think that looks a sensible approach. Note that the intent of that patch follows the thinking of leaving all defaults as before haltpoll governor was introduced, but once user modloads/uses cpuidle-haltpoll this governor then gets switched on. [0] https://lore.kernel.org/kvm/c8cf8dcc-76a3-3e15-f514-2cb9df1bbbdc@xxxxxxxxxx/ I would think a config-based preference on a governor would be good *if* one could actually switch idle governors at runtime like you can with cpufreq -- in case userspace wants something else other than the default. Right now we can't do that unless you toggle 'cpuidle_sysfs_switch', or picking one at boot with 'cpuidle.governor='. > May be I missed the point from some previous discussion but IMHO the > problem you are facing is coming from the design: there is no need to > create a halt governor but move the code inside the cpuidle-halt driver > instead and ignore the state asked by the governor and return the state > the driver entered. > Marcello's original patch series (first 3 revisions to be exact) actually had everything in the idle driver, but after some revisions (v4+) Rafael asked him to split the logic into a governor and unify it with poll state[1]. [1] https://lore.kernel.org/kvm/CAJZ5v0gPbSXB3r71XaT-4Q7LsiFO_UVymBwOmU8J1W5+COk_1g@xxxxxxxxxxxxxx/ Joao
