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[Haw Loeung <1579278@xxxxxxxxxxxxxxxxxx>]

Bug #1188647 enables Intel PSTATE by default.

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https://bugs.launchpad.net/bugs/1579278

Title:
  Consider changing default CPU frequency scaling governor back to
  "performance" (Ubuntu Server)

Status in linux package in Ubuntu:
  Invalid
Status in sysvinit package in Ubuntu:
  New
Status in linux source package in Xenial:
  Invalid
Status in sysvinit source package in Xenial:
  New

Bug description:
  Hi,

  With the new Ubuntu archive servers, we saw constantly high load and
  after some tinkering, we found that it was mostly CPUs being woken up
  to see if they should enter idle states. Changing the CPU frequency
  scaling governor to "performance" saw a considerable drop.

  Perf report using the following commands:

  | perf record -g -a sleep 10
  | perf report

  | Samples: 287K of event 'cycles:pp', Event count (approx.): 124776998906
  |   Children      Self  Command          Shared Object             Symbol
  | +   55.24%     0.20%  swapper          [kernel.kallsyms]         [k] cpu_startup_entry
  | +   53.51%     0.00%  swapper          [kernel.kallsyms]         [k] start_secondary
  | +   53.02%     0.08%  swapper          [kernel.kallsyms]         [k] call_cpuidle
  | +   52.94%     0.02%  swapper          [kernel.kallsyms]         [k] cpuidle_enter
  | +   31.81%     0.67%  swapper          [kernel.kallsyms]         [k] cpuidle_enter_state
  | +   29.59%     0.12%  swapper          [kernel.kallsyms]         [k] acpi_idle_enter
  | +   29.45%     0.05%  swapper          [kernel.kallsyms]         [k] acpi_idle_do_entry
  | +   29.43%    29.43%  swapper          [kernel.kallsyms]         [k] acpi_processor_ffh_cstate_enter
  | +   20.51%     0.04%  swapper          [kernel.kallsyms]         [k] ret_from_intr
  | +   20.47%     0.12%  swapper          [kernel.kallsyms]         [k] do_IRQ
  | +   19.30%     0.07%  swapper          [kernel.kallsyms]         [k] irq_exit
  | +   19.18%     0.07%  apache2          [kernel.kallsyms]         [k] entry_SYSCALL_64_fastpath
  | +   18.80%     0.17%  swapper          [kernel.kallsyms]         [k] __do_softirq
  | +   16.45%     0.11%  swapper          [kernel.kallsyms]         [k] net_rx_action
  | +   16.25%     0.43%  swapper          [kernel.kallsyms]         [k] be_poll
  | +   14.74%     0.21%  swapper          [kernel.kallsyms]         [k] be_process_rx
  | +   13.61%     0.07%  swapper          [kernel.kallsyms]         [k] napi_gro_frags
  | +   12.58%     0.04%  swapper          [kernel.kallsyms]         [k] netif_receive_skb_internal
  | +   12.48%     0.03%  swapper          [kernel.kallsyms]         [k] __netif_receive_skb
  | +   12.42%     0.24%  swapper          [kernel.kallsyms]         [k] __netif_receive_skb_core
  | +   12.41%     0.00%  apache2          [unknown]                 [k] 0x00007f27983b5028
  | +   12.41%     0.00%  apache2          [unknown]                 [k] 0x00007f2798369028
  | +   11.49%     0.16%  swapper          [kernel.kallsyms]         [k] ip_rcv
  | +   11.29%     0.09%  swapper          [kernel.kallsyms]         [k] ip_rcv_finish
  | +   10.77%     0.05%  swapper          [kernel.kallsyms]         [k] ip_local_deliver
  | +   10.70%     0.06%  swapper          [kernel.kallsyms]         [k] ip_local_deliver_finish
  | +   10.55%     0.22%  swapper          [kernel.kallsyms]         [k] tcp_v4_rcv
  | +   10.10%     0.00%  apache2          [unknown]                 [k] 0000000000000000
  | +   10.01%     0.04%  swapper          [kernel.kallsyms]         [k] tcp_v4_do_rcv

  Expanding in a few of those, you'll see:

  | -   55.24%     0.20%  swapper          [kernel.kallsyms]         [k] cpu_startup_entry
  |    - 55.04% cpu_startup_entry
  |       - 52.98% call_cpuidle
  |          + 52.93% cpuidle_enter
  |          + 0.00% ret_from_intr
  |            0.00% cpuidle_enter_state
  |            0.00% irq_entries_start
  |       + 1.14% cpuidle_select
  |       + 0.47% schedule_preempt_disabled
  |         0.10% rcu_idle_enter
  |         0.09% rcu_idle_exit
  |       + 0.05% ret_from_intr
  |       + 0.05% tick_nohz_idle_enter
  |       + 0.04% arch_cpu_idle_enter
  |         0.02% cpuidle_enter
  |         0.02% tick_check_broadcast_expired
  |       + 0.01% cpuidle_reflect
  |         0.01% menu_reflect
  |         0.01% atomic_notifier_call_chain
  |         0.01% local_touch_nmi
  |         0.01% cpuidle_not_available
  |         0.01% menu_select
  |         0.01% cpuidle_get_cpu_driver
  |       + 0.01% tick_nohz_idle_exit
  |       + 0.01% sched_ttwu_pending
  |         0.00% set_cpu_sd_state_idle
  |         0.00% native_irq_return_iret
  |         0.00% schedule
  |       + 0.00% arch_cpu_idle_exit
  |         0.00% __tick_nohz_idle_enter
  |         0.00% irq_entries_start
  |         0.00% sched_clock_idle_wakeup_event
  |         0.00% reschedule_interrupt
  |       + 0.00% apic_timer_interrupt
  |    + 0.20% start_secondary
  |    + 0.00% x86_64_start_kernel
  | +   53.51%     0.00%  swapper          [kernel.kallsyms]         [k] start_secondary
  | +   53.02%     0.08%  swapper          [kernel.kallsyms]         [k] call_cpuidle
  | -   52.94%     0.02%  swapper          [kernel.kallsyms]         [k] cpuidle_enter
  |    - 52.92% cpuidle_enter
  |       + 31.81% cpuidle_enter_state
  |       + 20.01% ret_from_intr
  |       + 0.51% apic_timer_interrupt
  |         0.28% native_irq_return_iret
  |       + 0.09% reschedule_interrupt
  |         0.05% irq_entries_start
  |         0.05% do_IRQ
  |         0.05% common_interrupt
  |         0.02% sched_idle_set_state
  |         0.01% acpi_idle_enter
  |         0.01% ktime_get
  |         0.01% restore_regs_and_iret
  |         0.01% restore_c_regs_and_iret
  |       + 0.01% call_function_single_interrupt
  |         0.00% native_iret
  |       + 0.00% call_function_interrupt
  |         0.00% smp_apic_timer_interrupt
  |         0.00% smp_reschedule_interrupt
  |         0.00% smp_call_function_single_interrupt
  |    + 0.02% start_secondary

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