Greetings,

I have an appliance with 2 CPU cores and 3 network interfaces. In my case,
eth0/eth1 are on an i210 and eth2 is on i211. The first 2 interfaces
(eth0/eth1) are acting as a bridge, and eth2 is normal. I am using Linux
kernel 3.18.20 and igb 5.3.3.2.

I am hunting down performance delays when traffic from eth2 is passing
through the eth0/eth1 bridge. I notice that all interrupts from all
adapters are occurring on CPU 0. I suspect that I can get a performance
boost if I distribute my interrupts across both CPU cores (similar to my
ixgbe based appliances). Is this possible through some configuration or
minor driver changes?

Here is a summary of my interrupts and a sample of my CPU affinity:

----------------- cut ----------------
# cat /proc/interrupts
            CPU0       CPU1
   0:         50          0   IO-APIC-edge      timer
   1:          3          0   IO-APIC-edge      i8042
   4:       2205          0   IO-APIC-edge      serial
   8:         13          0   IO-APIC-fasteoi   rtc0
   9:          0          0   IO-APIC-fasteoi   acpi
  12:          5          0   IO-APIC-edge      i8042
  18:          0          0   IO-APIC   18-fasteoi   i801_smbus
  23:         87          0   IO-APIC   23-fasteoi   ehci_hcd:usb1
  87:          4          0   PCI-MSI-edge      i915
  88:       5790          0   PCI-MSI-edge      0000:00:13.0
  89:          1          0   PCI-MSI-edge      eth0
  90:      13149          0   PCI-MSI-edge      eth0-TxRx-0
  91:       8221          0   PCI-MSI-edge      eth0-TxRx-1
  92:          1          0   PCI-MSI-edge      eth1
  93:      13379          0   PCI-MSI-edge      eth1-TxRx-0
  94:       8840          0   PCI-MSI-edge      eth1-TxRx-1
  95:        674          0   PCI-MSI-edge      eth2
  96:      11654          0   PCI-MSI-edge      eth2-TxRx-0
  97:       1674          0   PCI-MSI-edge      eth2-TxRx-1
  98:         64          0   PCI-MSI-edge      iwlwifi
 NMI:          3          3   Non-maskable interrupts
 LOC:     295147     249655   Local timer interrupts
 SPU:          0          0   Spurious interrupts
 PMI:          3          3   Performance monitoring interrupts
 IWI:          1          0   IRQ work interrupts
 RTR:          0          0   APIC ICR read retries
 RES:       1916       2172   Rescheduling interrupts
 CAL:        116       2390   Function call interrupts
 TLB:       1340       1345   TLB shootdowns
 TRM:          0          0   Thermal event interrupts
 THR:          0          0   Threshold APIC interrupts
 MCE:          0          0   Machine check exceptions
 MCP:          3          3   Machine check polls
 HYP:          0          0   Hypervisor callback interrupts
 ERR:          0
 MIS:          0
# cat /proc/irq/90/smp_affinity
3
----------------- cut ----------------

-- 
*Fred Klassen*
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