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SubjectRe: [PATCH v5 0/5] Track and expose idle PURR and SPURR ticks
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On 4/7/20 1:47 AM, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> Hi,
>
> This is the fifth version of the patches to track and expose idle PURR
> and SPURR ticks. These patches are required by tools such as lparstat
> to compute system utilization for capacity planning purposes.
>
> The previous versions can be found here:
> v4: https://lkml.org/lkml/2020/3/27/323
> v3: https://lkml.org/lkml/2020/3/11/331
> v2: https://lkml.org/lkml/2020/2/21/21
> v1: https://lore.kernel.org/patchwork/cover/1159341/
>
> They changes from v4 are:
>
> - As suggested by Naveen, moved the functions read_this_idle_purr()
> and read_this_idle_spurr() from Patch 2 and Patch 3 respectively
> to Patch 4 where it is invoked.
>
> - Dropped Patch 6 which cached the values of purr, spurr,
> idle_purr, idle_spurr in order to minimize the number of IPIs
> sent.
>
> - Updated the dates for the idle_purr, idle_spurr in the
> Documentation Patch 5.
>
> Motivation:
> ===========
> 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.
>
> These patches are required for enhancement to the lparstat utility
> that compute the CPU utilization based on PURR and SPURR which can be
> found here :
> https://groups.google.com/forum/#!topic/powerpc-utils-devel/fYRo69xO9r4
>
>
> With the patches, when lparstat is run on a LPAR running CPU-Hogs,
> =========================================================================
> sudo ./src/lparstat -E 1 3
>
> System Configuration
> type=Dedicated mode=Capped smt=8 lcpu=2 mem=4834112 kB cpus=0 ent=2.00
>
> ---Actual--- -Normalized-
> %busy %idle Frequency %busy %idle
> ------ ------ ------------- ------ ------
> 1 99.99 0.00 3.35GHz[111%] 110.99 0.00
> 2 100.00 0.00 3.35GHz[111%] 111.01 0.00
> 3 100.00 0.00 3.35GHz[111%] 111.00 0.00
>
> With patches, when lparstat is run on and idle LPAR
> =========================================================================
> System Configuration
> type=Dedicated mode=Capped smt=8 lcpu=2 mem=4834112 kB cpus=0 ent=2.00
> ---Actual--- -Normalized-
> %busy %idle Frequency %busy %idle
> ------ ------ ------------- ------ ------
> 1 0.15 99.84 2.17GHz[ 72%] 0.11 71.89
> 2 0.24 99.76 2.11GHz[ 70%] 0.18 69.82
> 3 0.24 99.75 2.11GHz[ 70%] 0.18 69.81
>
> Gautham R. Shenoy (5):
> powerpc: Move idle_loop_prolog()/epilog() functions to header file
> powerpc/idle: Store PURR snapshot in a per-cpu global variable
> powerpc/pseries: Account for SPURR ticks on idle CPUs
> powerpc/sysfs: Show idle_purr and idle_spurr for every CPU
> Documentation: Document sysfs interfaces purr, spurr, idle_purr,
> idle_spurr
>
> Documentation/ABI/testing/sysfs-devices-system-cpu | 39 +++++++++
> arch/powerpc/include/asm/idle.h | 93 ++++++++++++++++++++++
> arch/powerpc/kernel/sysfs.c | 82 ++++++++++++++++++-
> arch/powerpc/platforms/pseries/setup.c | 8 +-
> drivers/cpuidle/cpuidle-pseries.c | 39 ++-------
> 5 files changed, 224 insertions(+), 37 deletions(-)
> create mode 100644 arch/powerpc/include/asm/idle.h
>

Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>

Any chance this is going to be merged in the near future? There is a patchset to
update lparstat in the powerpc-utils package to calculate PURR/SPURR cpu
utilization that I would like to merge, but have been holding off to make sure
we are synced with this proposed patchset.

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