[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/2] cpufreq, powernow: enable/disable core performance boost for all cpus in policy
>>> On 20.06.13 at 17:32, Jacob Shin <jacob.shin@xxxxxxx> wrote: > On Thu, Jun 20, 2013 at 08:54:00AM +0100, Jan Beulich wrote: >> >>> On 20.06.13 at 01:07, Jacob Shin <jacob.shin@xxxxxxx> wrote: >> > On Wed, Jun 19, 2013 at 03:14:46PM -0500, Jacob Shin wrote: >> >> Currently, enable/disable turbo mode on AMD is broken: >> >> >> >> $ xenpm enable-turbo-mode 0 <-- works and proper CPU MSR bit is set >> >> $ xenpm enable-turbo-mode 1 <-- silently broken, MSR bit not set >> >> >> >> Since ->turbo is per policy, when user requests to enable/disable >> >> turbo mode, we need to set the bit in all of the ->cpus that this >> >> policy affects. >> > >> > Sorry, I'll have to re-do this [PATCH 1/2], as it does not solve the >> > problem on platforms with a separate policy per CPU. >> >> But isn't a separate policy per CPU meaning that indeed you want >> to only fiddle with the one CPU that the policy is getting changed >> for? > > Yes, this is okay if the end user realizes that on current AMD parts, > disabling turbo on one core means that it affects all other sibling > cores that are on the same node. > > $ xenpm disable-turbo-mode 0 </-- hardware bit gets set on CPU0 > $ xenpm get-cpufreq-para > ... > CPU0 > turbo mode: disabled > ... > CPU1 > turbo mode: enabled > > But since CPU0 and CPU1 are in the same Node, in reality CPU1 also in > affect has turbo mode disabled. > > If this is okay, then I think the above patch will be fine. No, this is not okay, but it is also not okay to reflect such a setup with a per-core policy. Of course things are going to become difficult if frequency selection can be per-core, but turbo mode enabling requires that all cores have it enabled in order for it to actually be used. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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