linux-kernel - [PATCH 0/2] measure latency of cpu hotplug path

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Date:   Wed, 23 Sep 2020 16:37:44 -0700
From:   Prasad Sodagudi <psodagud@...eaurora.org>
To:     rostedt@...dmis.org, tglx@...utronix.de, qais.yousef@....com,
        peterz@...radead.org, mingo@...nel.org, cai@....pw,
        tyhicks@...onical.com, arnd@...db.de
Cc:     rameezmustafa@...eaurora.org, linux-kernel@...r.kernel.org,
        Prasad Sodagudi <psodagud@...eaurora.org>
Subject: [PATCH 0/2] measure latency of cpu hotplug path

There are all changes related to cpu hotplug path and would like to seek
upstream review. These are all patches in Qualcomm downstream kernel
for a quite long time. First patch sets the rt prioity to hotplug
task and second patch adds cpuhp trace events.

1) cpu-hotplug: Always use real time scheduling when hotplugging a CPU
2) cpu/hotplug: Add cpuhp_latency trace event

Example logs:-  
cpu online -
         cpuhp/4-200   [004] ....   223.891886: cpuhp_enter: cpu: 0004 target: 213 step: 212 (sched_cpu_activate)
         cpuhp/4-200   [004] ....   223.891894: cpuhp_exit:  cpu: 0004  state: 212 step: 212 ret: 0
              sh-176   [000] ....   223.891912: cpuhp_exit:  cpu: 0004  state: 213 step:  86 ret: 0
              sh-176   [000] ....   223.891915: cpuhp_latency:  cpu:4 state:online latency:3874 USEC ret: 0

cpu offline - 
              sh-176   [000] ....   265.193490: cpuhp_exit:  cpu: 0004  state:   2 step:   2 ret: 0
              sh-176   [000] ....   265.193494: cpuhp_latency:  cpu:4 state:offline latency:57431 USEC ret: 0


Prasad Sodagudi (1):
  cpu/hotplug: Add cpuhp_latency trace event

Syed Rameez Mustafa (1):
  cpu-hotplug: Always use real time scheduling when hotplugging a CPU

 include/trace/events/cpuhp.h | 29 +++++++++++++++++++++++++
 kernel/cpu.c                 | 50 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)

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