[Bug 1579278] Re: Keep powersave CPU frequency scaling governor for CPUs that support intel_pstate

[fish]

On my Dell XPS 13 (i7-6500U) the only governors available are
performance and powersave. Ubuntu 16.04 seems to set this always to
'powersave' for me. This causes the CPU to clock down to 300-400Mhz when
idle. Unfortunately it's not clocking up again when under load
sometimes. Setting the governor to performance 'fixes' it.

I don't know if this is *this* issue or another one, so happy to open a
new issue if you prefer.

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Title:
  Keep powersave CPU frequency scaling governor for CPUs that support
  intel_pstate

Status in linux package in Ubuntu:
  Invalid
Status in systemd package in Ubuntu:
  Fix Released
Status in sysvinit package in Ubuntu:
  Invalid
Status in linux source package in Xenial:
  Invalid
Status in systemd source package in Xenial:
  Invalid
Status in sysvinit source package in Xenial:
  Triaged

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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