git: jme: Improve tiny packets transmission performance on low frequency CPU

[Sepherosa Ziehau]

commit 3a65efa657c814b3133903580145cbd07120e46c
Author: Sepherosa Ziehau <sephe at dragonflybsd.org>
Date:   Mon Dec 3 09:53:20 2012 +0800

    jme: Improve tiny packets transmission performance on low frequency CPU
    
    Update TXCSR register a little bit often; mainly to improve timeliness of
    packets transmission:
    The TXCSR register is updated after certain amount of TX descriptors are
    added to the hardware TX ring.  The default value of the amount of TX
    descriptors are 16.  This value could be further tuned by per-device sysctl
    node hw.jmeX.tx_wreg.
    
    The default value improves tiny packets transmission performance w/ JMC250
    on AMD970 at 2200Mhz (831Kpps -> 911Kpps), on AMD970 at 800Mhz (484Kpps -> 834Kpps)
    and it does not increase CPU usage on AMD970 at 3500Mhz (CPU usage stays @26%,
    JMC250 could only do 911Kpps).

Summary of changes:
 sys/dev/netif/jme/if_jme.c    |   28 ++++++++++++++++++++++------
 sys/dev/netif/jme/if_jmevar.h |    1 +
 2 files changed, 23 insertions(+), 6 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/3a65efa657c814b3133903580145cbd07120e46c


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