irq256 ????

[Erik Trulsson]

On Thu, Oct 09, 2008 at 10:51:36PM +0200, Zahemszky Gábor wrote:
> Hi!
> 
> I've just found in my machine's vmstat -i output:
> 
> ===
> $ vmstat -i
> interrupt                          total       rate
> irq1: atkbd0                       15524          0
> irq6: fdc0                            14          0
> irq12: psm0                       279947         16
> irq15: ata1                        41835          2
> irq16: uhci0 drm0                1407076         81
> irq17: atapci0                    257828         14
> irq19: fwohci0++                      16          0
> irq21: uhci1 ahc0+                 41712          2
> irq22: pcm0                        52848          3
> irq23: uhci2 ehci1                     1          0
> cpu0: timer                     33503897       1929
> 
> 
> irq256: em0                        42054          2
> 
> ===^
> 
> cpu1: timer                     33495040       1928
> Total                           69137792       3981
> $ dmesg|fgrep em0
> em0: <Intel(R) PRO/1000 Network Connection 6.9.5> port 0x30c0-0x30df
> mem 0x90300000-0x9031ffff,0x90324000-0x90324fff irq 20 at device 25.0 on pci0 
> em0: Using MSI interrupt em0: [FILTER]
> em0: Ethernet address: 00:19:d1:25:78:0a
> $ uname -a
> FreeBSD XXX 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #0: Thu Oct  2 21:35:45 CEST 2008
> root at XXX:/usr/obj/usr/src/sys/GENERIC  i386 $ 
> ====
> 
> What's that? (world and kernel are in sync)

It is an MSI-style interrupt [MSI=Message Signaled Interrupt] (available on
PCI-E devices and a few PCI/PCI-X devices.) They get allocated fake
irq-numbers starting at 256.

I.e. it is a feature, and a bug or indication of any problem.





-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se