Date: Wed, 21 Sep 2005 16:54:13 +0800 From: "Mao Shou Yan" <david.mao@thomson.net> To: <freebsd-net@freebsd.org> Subject: About guideline of parameters tuning while in polling mode. Message-ID: <31021C278A7A6B4AB95E9A085C3552181CE58F@bjngsmail01>
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Hi, everybody
Can anyone give some guidelines on tuning the following
parameters when the system is in polling mode and works in high
throughput network environment.
Thanks a lot!
/*
* EM_TIDV - Transmit Interrupt Delay Value
* Valid Range: 0-65535 (0=off)
* Default Value: 64
* This value delays the generation of transmit interrupts in units of
* 1.024 microseconds. Transmit interrupt reduction can improve CPU
* efficiency if properly tuned for specific network traffic. If the
* system is reporting dropped transmits, this value may be set too
high
* causing the driver to run out of available transmit descriptors.
*/
#define EM_TIDV 64
/*
* EM_TADV - Transmit Absolute Interrupt Delay Value (Not valid for
82542/82543/82544)
* Valid Range: 0-65535 (0=off)
* Default Value: 64
* This value, in units of 1.024 microseconds, limits the delay in
which a
* transmit interrupt is generated. Useful only if EM_TIDV is
non-zero,
* this value ensures that an interrupt is generated after the initial
* packet is sent on the wire within the set amount of time. Proper
tuning,
* along with EM_TIDV, may improve traffic throughput in specific
* network conditions.
*/
#define EM_TADV 64
/*
* EM_RDTR - Receive Interrupt Delay Timer (Packet Timer)
* Valid Range: 0-65535 (0=off)
* Default Value: 0
* This value delays the generation of receive interrupts in units of
1.024
* microseconds. Receive interrupt reduction can improve CPU
efficiency if
* properly tuned for specific network traffic. Increasing this value
adds
* extra latency to frame reception and can end up decreasing the
throughput
* of TCP traffic. If the system is reporting dropped receives, this
value
* may be set too high, causing the driver to run out of available
receive
* descriptors.
*
* CAUTION: When setting EM_RDTR to a value other than 0, adapters
* may hang (stop transmitting) under certain network
conditions.
* If this occurs a WATCHDOG message is logged in the system
event log.
* In addition, the controller is automatically reset,
restoring the
* network connection. To eliminate the potential for the
hang
* ensure that EM_RDTR is set to 0.
*/
#define EM_RDTR 0
/*
* Receive Interrupt Absolute Delay Timer (Not valid for
82542/82543/82544)
* Valid Range: 0-65535 (0=off)
* Default Value: 64
* This value, in units of 1.024 microseconds, limits the delay in
which a
* receive interrupt is generated. Useful only if EM_RDTR is non-zero,
* this value ensures that an interrupt is generated after the initial
* packet is received within the set amount of time. Proper tuning,
* along with EM_RDTR, may improve traffic throughput in specific
network
* conditions.
*/
#define EM_RADV 64
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