git: NFE - Change default RX ring size from 128 -> 256, Adjust moderation timer.

[Matthew Dillon]

commit 5df3a6aa72f98f69fa498e2249e71d7a14a0f16f
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Wed Sep 9 09:10:58 2009 -0700

    NFE - Change default RX ring size from 128 -> 256, Adjust moderation timer.
    
    * NFE does not seem to be able to flow control the phy.  TCP reception
      using window scaling and large socket bufs can blow out the receiver ring
      before the interrupt has a chance to drain it.
    
      This results in the receiver dropping a packet and the transmitter
      seeing bursts of duplicate TCP acks and having to go into recovery.
    
    * Shorten the moderation timer from 500uS to 250uS, increasing its
      frequency from 2000Hz to 4000Hz.  Note that the moderation timer
      only kicks in when the discrete interrupt rate exceeds the frequency.
    
    * The problem still occurs with the larger RX ring and shorter moderation
      timer, but not nearly as often.

Summary of changes:
 sys/dev/netif/nfe/if_nfe.c    |    7 ++++---
 sys/dev/netif/nfe/if_nfereg.h |    2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/5df3a6aa72f98f69fa498e2249e71d7a14a0f16f


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