Re: High IRQ usage on CPU 0

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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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