Public bug reported:
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
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Incomplete
** Affects: linux (Ubuntu Xenial)
Importance: Undecided
Status: Incomplete
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https://bugs.launchpad.net/bugs/1579278
Title:
Consider changing default CPU frequency scaling governor back to
"performance"
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