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SubjectRe: High IRQ usage on CPU 0
On Fri, Jun 24, 2011 at 02:04:41PM -0500, Shawn Bohrer wrote:
> Running 3.0.0-rc4+ I noticed I'm seeing the following on an idle Dell
> r610 system:
>
> Cpu0 : 0.0%us, 0.0%sy, 0.0%ni, 64.3%id, 0.0%wa, 35.7%hi, 0.0%si, 0.0%st
> Cpu1 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu2 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu3 : 0.0%us, 0.0%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.3%hi, 0.3%si, 0.0%st
> Cpu4 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu5 : 0.0%us, 0.0%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.3%hi, 0.3%si, 0.0%st
> Cpu6 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu7 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
> Cpu8 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu9 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu10 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu11 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
> Cpu12 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
> Cpu13 : 0.0%us, 0.0%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.3%hi, 0.3%si, 0.0%st
> Cpu14 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st
> Cpu15 : 0.0%us, 0.0%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.3%hi, 0.0%si, 0.0%st
>
> Watching /proc/interrupts it looks like most of the interrupts on CPU0
> are on IRQ 0 from "IO-APIC-edge timer".
>
> perf top -C 0 shows:
>
> ---------------------------------------------------------------------
> PerfTop: 1024 irqs/sec kernel:100.0% exact: 0.0% [1000Hz cycles], (all, CPU: 0)
> ---------------------------------------------------------------------
>
> samples pcnt function DSO
> _______ _____ ___________________________________ _______
>
> 11648.00 83.6% default_send_IPI_mask_sequence_phys vmlinux
> 1548.00 11.1% _raw_spin_lock_irqsave vmlinux
> 530.00 3.8% intel_idle vmlinux
> 36.00 0.3% hpet_legacy_next_event vmlinux
> 28.00 0.2% tick_handle_oneshot_broadcast vmlinux
> 20.00 0.1% find_next_bit vmlinux
> 16.00 0.1% find_busiest_group vmlinux
> 15.00 0.1% _raw_spin_unlock_irqrestore vmlinux
> 13.00 0.1% cpuidle_idle_call vmlinux
> 10.00 0.1% _raw_spin_lock vmlinux
> 9.00 0.1% tick_broadcast_oneshot_control vmlinux
> 8.00 0.1% notifier_call_chain vmlinux
> 7.00 0.1% leave_mm vmlinux
>
> For some reason 'perf record -C 0 -g sleep 5' doesn't record anything,
> but here is the top functions from a 'perf record -a -g sleep 5':
>
> # Events: 77K cycles
> #
> # Overhead Command Shared Object Symbol
> # ........ ............... .................. ...................................
> #
> 80.22% swapper [kernel.kallsyms] [k] _raw_spin_lock_irqsave
> |
> --- _raw_spin_lock_irqsave
> |
> |--89.92%-- clockevents_notify
> | intel_idle
> | cpuidle_idle_call
> | cpu_idle
> | |
> | |--98.67%-- start_secondary
> | |
> | --1.33%-- rest_init
> | start_kernel
> | x86_64_start_reservations
> | x86_64_start_kernel
> |
> |--10.03%-- tick_broadcast_oneshot_control
> | tick_notify
> | notifier_call_chain
> | raw_notifier_call_chain
> | clockevents_notify
> | intel_idle
> | cpuidle_idle_call
> | cpu_idle
> | |
> | |--99.97%-- start_secondary
> | --0.03%-- [...]
> --0.05%-- [...]
>
> 9.32% swapper [kernel.kallsyms] [k] default_send_IPI_mask_sequence_phys
> |
> --- default_send_IPI_mask_sequence_phys
> physflat_send_IPI_mask
> lapic_timer_broadcast
> tick_do_broadcast
> tick_handle_oneshot_broadcast
> timer_interrupt
> handle_irq_event_percpu
> handle_irq_event
> handle_edge_irq
> handle_irq
> do_IRQ
> common_interrupt
> |
> |--99.91%-- cpuidle_idle_call
> | cpu_idle
> | rest_init
> | start_kernel
> | x86_64_start_reservations
> | x86_64_start_kernel
> --0.09%-- [...]
>
> 5.83% swapper [kernel.kallsyms] [k] intel_idle
> |
> --- intel_idle
> |
> |--99.67%-- cpuidle_idle_call
> | cpu_idle
> | |
> | |--94.19%-- start_secondary
> | |
> | --5.81%-- rest_init
> | start_kernel
> | x86_64_start_reservations
> | x86_64_start_kernel
> --0.33%-- [...]
>
> I'm not sure what other information would be useful here. Please let
> me know if you need anything else.

The above info was taken with CONFIG_INTEL_IDLE=y, unsetting this
config option makes the problem go away.

Here is some more info about the system that may be relevant.

$ cat /proc/cpuinfo | grep model | sort -u
model: 26
model name: Intel(R) Xeon(R) CPU X5570 @ 2.93GHz

$ dmesg | grep command
Kernel command line: ro root=/dev/sda2 selinux=0 audit=0 processor.max_cstate=0 crashkernel=128M

$ sudo omreport chassis biossetup
BIOS Setup

General
Boot Sequence : Hard drive C:
Num Lock : On
User Accessible USB Ports : All Ports On
Processor Virtualization Technology : Disabled
Processor Logical Processor (HyperThreading) : Enabled
AC Power Recovery Mode : On
Embedded SATA Controller : Off
SATA Port 0 : Off
Dual NIC (1/2) : Enabled with 1st NIC PXE and 2nd NIC None
Dual NIC (3/4) : Enabled with 1st NIC None and 2nd NIC None
TPM Security : Off
Internal USB Port : Enabled
OS Watchdog Timer : Disabled
Processor Core Based Turbo Mode : Enabled
Node Interleaving : Disabled
Processor Execute Disable : Enabled
Processor CMP : 4
Boot Mode : BIOS
Processor C State Control : Enabled
Processor C1-E : Disabled

Serial Communications
Serial Communications : On without Console Redirection
Console Redirection After Boot : Enabled
External Serial Connector : Serial Device1
Console Redirection Failsafe BAUD Rate : 115200
Serial Address Select : Serial Device1=COM1, Serial Device2=COM2

--
Shawn



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