From: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
To: Nathan Lynch <nathanl@linux.ibm.com>,
"Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>,
linux-kernel@vger.kernel.org,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 0/3] pseries: Track and expose idle PURR and SPURR ticks
Date: Thu, 5 Dec 2019 20:33:23 +0530 [thread overview]
Message-ID: <48823589-b105-0da3-e532-f633ade8f0d9@linux.vnet.ibm.com> (raw)
In-Reply-To: <87r21ju3ud.fsf@linux.ibm.com>
On 12/5/19 3:54 AM, Nathan Lynch wrote:
> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:
>> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>>
>> On PSeries LPARs, the data centers planners desire a more accurate
>> view of system utilization per resource such as CPU to plan the system
>> capacity requirements better. Such accuracy can be obtained by reading
>> PURR/SPURR registers for CPU resource utilization.
>>
>> 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.
--
Kamalesh
next prev parent reply other threads:[~2019-12-05 15:08 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 12:01 [PATCH 0/3] pseries: Track and expose idle PURR and SPURR ticks Gautham R. Shenoy
2019-11-27 12:01 ` [PATCH 1/3] powerpc/pseries: Account for SPURR ticks on idle CPUs Gautham R. Shenoy
2019-12-03 13:39 ` Kamalesh Babulal
2019-12-04 22:24 ` Nathan Lynch
2020-02-03 4:45 ` Gautham R Shenoy
2019-11-27 12:01 ` [PATCH 2/3] powerpc/sysfs: Show idle_purr and idle_spurr for every CPU Gautham R. Shenoy
2019-12-03 13:37 ` Kamalesh Babulal
2019-12-04 12:37 ` Gautham R Shenoy
2019-12-03 21:02 ` kbuild test robot
2019-12-04 22:24 ` Nathan Lynch
2020-02-03 4:47 ` Gautham R Shenoy
2019-12-05 16:53 ` Naveen N. Rao
2020-02-03 4:50 ` Gautham R Shenoy
2020-02-04 7:52 ` Naveen N. Rao
2020-02-05 4:19 ` Gautham R Shenoy
2020-02-05 6:58 ` Naveen N. Rao
2020-02-05 7:08 ` Christophe Leroy
2020-02-05 8:07 ` Naveen N. Rao
2019-11-27 12:01 ` [PATCH 3/3] Documentation: Document sysfs interfaces purr, spurr, idle_purr, idle_spurr Gautham R. Shenoy
2019-12-04 22:25 ` Nathan Lynch
2019-12-04 22:24 ` [PATCH 0/3] pseries: Track and expose idle PURR and SPURR ticks Nathan Lynch
2019-12-05 15:03 ` Kamalesh Babulal [this message]
2019-12-05 16:16 ` Nathan Lynch
2019-12-05 17:25 ` Naveen N. Rao
2019-12-06 9:14 ` Naveen N. Rao
2020-02-04 9:12 ` Kamalesh Babulal
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