@Haw Loeung: It would be good to understand in more detail your findings. As far as I know (and I am not an expert in this area), great care has been taken to avoid things like wakeups just to decide to go idle.
I did a test on my computer (Ubuntu 16.04 server, no GUI), but to avoid extra overheads, I used the /proc/timer_stats method. I also did the test over 300 seconds, so as to dilute influence from the command itself. Kernel: 4.8.0-040800rc5-generic intel_pstate, "idle" system: powersave: 14722 events, 49.073 events / second performance: 14964 events, 49.879 events / second intel_pstate: extra "idle" system: powersave: 6381 total events, 21.269 events / second performance: 6788 events, 22.626 events / second Which kernel are you using? There was a flurry of high wakeups activity in June, but I thought it all got resolved. Note that there was a slight increase in wakeups with the recent change to a utilization based algorithm, but that was good thing because it solved a very long standing issue whereby the CPU frequency might not increase under high load for periodic workflows that just so happened to be idle on jiffy boundaries. You mention "on some workloads". Could you be more specific? i.e. so that I can attempt to recreate your scenario on my computer. My script: $ cat ./set_cpu_timer_stats_2 #! /bin/bash # Take a 300 second time sample # A long time is needed to amortize/dilute the effect of the command itself. # Reset the counters echo "0" > /proc/timer_stats echo "1" > /proc/timer_stats # Now let the sample time elapse sleep 300 # Now observe the timer counters cat /proc/timer_stats # And turn off timer stats. echo "0" > /proc/timer_stats What does "extra idle" mean?: $ cat set_cpu_turn_off_services #! /bin/bash # Turn off some services to try to get "idle" to be more "idle" sudo systemctl stop mysql.service sudo systemctl stop apache2.service sudo systemctl stop nmbd.service sudo systemctl stop smbd.service sudo systemctl stop cron.service sudo systemctl stop winbind.service sudo systemctl stop apt-daily.timer Recent wakeups thread: http://marc.info/?t=146617757000003&r=1&w=2 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1579278 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 Committed 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1579278/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
