Interrupt storms with wm(4)

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

Hello

After batteling with a Xen virtulalized IPfilter machine that froze
(see http://mail-index.netbsd.org/port-xen/2021/10/07/msg010185.html),
I tried to unvirtualize it and moved it to real hardware. It now 
exhibits interrupts storms that sometimes lead to a freeze. 

The wm0 interface gets a lot of interrupts. On low usage, CPU
is spent around 10% in interrupts. It can rise to more than 80%.
See below what systat vm says when the machine is quiet. 
ioapic0 pin 16 is the wm0 interface.

I tried NetBSD 9.2/i386 with options  NO_PCI_MSI_MSIX, 
WM_DISABLE_MSI=1 and WM_DISABLE_MSIX=1 without improvement. 
I also tried NetBSD-current/i386 GENERIC, same behavior.

Any idea of what could I try to improve the situation?

Here is what dmesg said about wm0:
wm0 at pci0 dev 25 function 0: 82801I (AMT) LAN Controller (rev. 0x02)
wm0: interrupting at ioapic0 pin 16
wm0: PCI-Express bus
wm0: 2048 words FLASH, version 1.1.0
wm0: Ethernet address 00:30:48:de:cc:4c
wm0: 0x2a4480<FLASH,IOH_VALID,PCIE,ASF_FIRM,AMT,WOL>

And here is an idle vmstat:
    3 users    Load  0.21  0.18  0.09                  Fri Oct 15 04:02:42

Proc:r  d  s        Csw  Traps SysCal  Intr   Soft  Fault     PAGING   SWAPPING
           9         20           211  1315   1399            in  out   in  out
                                                        ops
   0.0% Sy   0.0% Us   0.0% Ni  12.0% In  88.0% Id    pages
|    |    |    |    |    |    |    |    |    |    |
%%%%%%                                                                    forks
                                                                          fkppw
Anon       109976   3%   zero  2744312      1415 Interrupts               fksvm
Exec        30116    %   wired   11104           TLB shootdown            pwait
File        75312   2%   inact               100 cpu0 timer               relck
Meta         9293    %   bufs      646           ioapic0 pin 9            rlkok
 (kB)        real   swaponly      free      1147 ioapic0 pin 16           noram
Active     204300              2797228           msi1 vec 0               ndcpy
Namei         Sys-cache     Proc-cache       168 ioapic0 pin 4            fltcp
    Calls     hits    %     hits     %                                    zfod
        6        6  100                                                   cow
                                                                      512 fmin
  Disks:     wd0     wd1     cd0   raid0                              682 ftarg
 seeks                                                                    itarg
 xfers                                                                    flnan
 bytes                                                                    pdfre





-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost