High interrupt %

R

romeor

Hello,

The top shows 25,7% interrupt after upgrading to 8.3-p2 last week. I just didn't pay any attention until today.

[CMD=]systat -vmstat 1[/CMD]

Code: 
    1 users    Load  0.00  0.00  0.00                  Jun 12 11:28

Mem:KB    REAL            VIRTUAL                       VN PAGER   SWAP PAGER
        Tot   Share      Tot    Share    Free           in   out     in   out
Act   82344    7596   405456     8292 1911988  count
All  119280    7904 1074214k    13016          pages
Proc:                                                            Interrupts
  r   p   d   s   w   Csw  Trp  Sys  Int  Sof  Flt        cow    4104 total
             31      2311   11  479  102 1016    4      4 zfod     51 em1 irq17
                                                          ozfod     1 uhci1+ 19
 1.1%Sys  25.0%Intr  0.0%User  0.0%Nice 73.9%Idle        %ozfod       uhci0 ehci
|    |    |    |    |    |    |    |    |    |    |       daefr  2001 cpu0: time
=++++++++++++                                             prcfr    50 em0 irq256
                                        10 dtbuf          totfr  2001 cpu1: time
Namei     Name-cache   Dir-cache    142984 desvn          react
   Calls    hits   %    hits   %    128031 numvn          pdwak
                                     35746 frevn          pdpgs
                                                          intrn
Disks   ad4   ad6                                  440112 wire
KB/t   0.00  0.50                                   89340 act
tps       0     1                                 1595420 inact
MB/s   0.00  0.00                                     560 cache
%busy     0     0                                 1911428 free
                                                   427584 buf

[CMD=]vmstat -i[/CMD]
Code: 
interrupt                          total       rate
irq17: em1                      37169198         68
irq19: uhci1+                    3715368          6
irq23: uhci0 ehci0                     1          0
cpu0: timer                   1087085405       1998
irq256: em0                     31027314         57
cpu1: timer                   1087082311       1998
Total                         2246079597       4128
Can someone help me to find the reason of this rate? This server is a gateway for small network. It runs on Intel(R) Pentium(R) 4 CPU 3.00GHz (3002.91-MHz K8-class CPU).
 
Are you saying the interrupt load percentage increased after the upgrade? If so, what was it before?

There is nothing inherently bad about spending 25% of the CPU time servicing interrupts, as long as overall system performance is OK. If you are concerned about it, have you tried reducing HZ to reduce the large number of timer interrupts?
 
Before update it was around 0,25-0,6 %, as there is almost no traffic behind this gateway. I don't have HZ stuff in my kernel configuration as there should be no need of that on a gateway with 2-3 Mbit/s traffic. So how can one find what causes this interrupt, as those commands show nothing useful?
 
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