Messages in this thread |  | | From | Nathan Lynch <> | Subject | Re: [PATCH 0/3] pseries: Track and expose idle PURR and SPURR ticks | Date | Thu, 05 Dec 2019 10:16:19 -0600 |
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Hi Kamalesh,
Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> writes: > On 12/5/19 3:54 AM, Nathan Lynch wrote: >> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes: >>> >>> Tools such as lparstat which are used to compute the utilization need >>> to know [S]PURR ticks when the cpu was busy or idle. The [S]PURR >>> counters are already exposed through sysfs. We already account for >>> PURR ticks when we go to idle so that we can update the VPA area. This >>> patchset extends support to account for SPURR ticks when idle, and >>> expose both via per-cpu sysfs files. >> >> Does anything really want to use PURR instead of SPURR? Seems like we >> should expose only SPURR idle values if possible. >> > > lparstat is one of the consumers of PURR idle metric > (https://groups.google.com/forum/#!topic/powerpc-utils-devel/fYRo69xO9r4). > Agree, on the argument that system utilization metrics based on SPURR > accounting is accurate in comparison to PURR, which isn't proportional to > CPU frequency. PURR has been traditionally used to understand the system > utilization, whereas SPURR is used for understanding how much capacity is > left/exceeding in the system based on the current power saving mode.
I'll phrase my question differently: does SPURR complement or supercede PURR? You seem to be saying they serve different purposes. If PURR is actually useful rather then vestigial then I have no objection to exposing idle_purr.
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