High Interrupts per second Troubleshooting

This document (7002721) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server 11

Situation

A high number of interrupts per second are observed.

#==[ Command ]======================================#
# /usr/bin/vmstat 1 4                                    vvvvv
procs -----------memory---------- ---swap-- -----io----   -system-- -----cpu------
r b   swpd   free   buff cache   si    so    bi    bo    in    cs us sy id wa st
1 1 373704   7156   1296   4144   47    78   139    92 2450   574 9 27 64 0 0
24 16 376664   6924   1360   3152 532 3104   552 3356 18101 33269 3 97 0 0 0
15 15 386388   6788   1356   5260 5872 10212 8656 10284 17623 39149 2 96 0 1 0
10 10 389896   6720   1232   3244 2384 3584 2532 3640 18893 17113 11 89 0 0 0
                                                         ^^^^^

Resolution

If your system experiences more than 10,000 interrupts per second you should account for them. Generally speaking a high number of interrupts per second indicates a problem with hardware. It could indicate a software bug in the case of software interrupts. If your system is performing as expected, then you don't really need to worry about high interrupts. Look at the procinfo command output to narrow down where the high interrupts are coming from.

NOTE: The procinfo package is not installed by default on SLES 15. Install it before running a supportconfig.

# zypper install procinfo

#==[ Command ]======================================#
# /usr/bin/procinfo
Linux 2.6.16.60-0.21-default (geeko@buildhost) (gcc 4.1.2 20070115) #1 1CPU [sles10sp2]

Memory:      Total        Used        Free      Shared     Buffers
Mem:        776380      282212      494168           0        3060
Swap:      1164672      127300     1037372

Bootup: Fri Feb 20 10:01:32 2009    Load average: 358.38 684.55 657.44 1/922 26155

user :       0:19:02.40   8.3% page in :    4329495 disk 1:   345167r   57598w
nice :       0:00:05.10   0.0% page out:    1834648 disk 2:       97r     362w
system:       0:30:36.43 13.4% page act:     397986
IOwait:       0:00:13.29   0.1% page dea:    1242187
hw irq:       0:00:08.72   0.1% page flt:    7741915
sw irq:       0:32:47.66 14.3% swap in :     715353
idle :       2:16:20.71 59.5% swap out:     409390
uptime:       3:49:08.45         context :   12105392

irq 0:   3288376 timer                 irq 8:         2 rtc
irq 1:      7108 i8042                 irq 9:         0 acpi
irq 3:         1                       irq 12:      3749 i8042
irq 4:         1                       irq 15:    128222 ide1
irq 6:         4                       irq169:    343932 ioc0
irq 7:         0 parport0              irq177: 28216486 eth0
                                        ^^^^^^^^^^^^^^^^^^^^^^

From this example, irq177 (eth0) is generating the most interrupts. You might consider replacing the network card. You might also consider updating the network kernel driver.

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