0 Replies Latest reply on Oct 1, 2013 11:54 AM by bmich

    82599EB / Interrupt Assignment Under Linux

    bmich

      Hello:

       

      I'm using an 82599 EB 10Gigabit controller (with X520-2 Ethernet Server Adapter) under Linux.  I'm trying to understand the RX and TX IRQ assignment.

       

      Note I am using a dual Intel Xeon X5670 system - thus 24 threads/CPUs.  What I see are 24 + 1 IRQs per port.

       

      # cat /proc/interrupts | grep p2p1

      167:         13          0         30       7046          0         50          0          0          0          0          0          0         27          0          0          0          0          0          0          0          0          0          0          0   PCI-MSI-edge     p2p1-TxRx-0

      .

      .

      .

      190:         13          0          0       7143          0          0          0          0          0          0          0          0          0         10          0          0          0          0          0          0          0          0          0          0   PCI-MSI-edge      p2p1-TxRx-23

      191:          4          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0   PCI-MSI-edge     p2p1


      Questions:


      1.  Why do the RX/TX use the same IRQ instead of one IRQ for Tx and a separate one for Rx ?

       

      2.  Do each of the 24 IRQs correspond to a different queue?

       

      3.  Given the 24 threads, I see one p2p1-TxRx IRQ for each processor.  But then there is a 25th one... what is its purpose given the other 24 seem to be tied to TxRx activity?

       

      191:          4          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0   PCI-MSI-edge     p2p1 <---- What is the purpose of this IRQ?

       

      Thank you