Publishing Venue
The IP.com Prior Art Database
Abstract
Disclosed is a method for operation-based adaptive transmit interrupt moderation. Benefits include improved performance.
Method
for operation-based adaptive transmit interrupt moderation
Disclosed is a
method for operation-based adaptive transmit interrupt moderation. Benefits
include improved performance.
Background
High-speed I/O
controllers, such as gigabit Ethernet adapters, are capable of generating tens
of thousands of interrupts per second. Generating interrupts at a rate this
high significantly reduces overall system performance because the system spends
a majority of its time servicing interrupts.
To alleviate this
situation, most conventional high-speed I/O controllers implement a method of
interrupt moderation. One method starts a countdown each time a transmit
operation is completed. If the countdown expires before a subsequent transmit
operation is completed, an interrupt is asserted. However, if the operation is
completed, the countdown starts over. This approach enables bursts of packets
to be completed and a single interrupt to be asserted to indicate that the
burst has been transmitted. The countdown value is determined by a programmable
register and is the same for all operations. This countdown’s starting value is
referred to as the transmit interrupt delay value (TIDV). With standard
Ethernet packets, this method works well. Packet size is constrained to 1522
bytes or less.
Two changes in
the networking industry complicate the conventional solution, transmission
control protocol (TCP) segmentation offload and jumbo frames. TCP segmentation
offload (TSO or Large Send) enables a single transmit operation to result in
multiple packets being sent on the network. The work of formatting data into
packets (packetizing) is offloaded to the I/O controller. TSO enables large
chunks of data (up to the size of a TCP window) to be given to the I/O
controller as a single transmit operation. Jumbo frames are Ethernet packets
that are larger than those defined by the 802.3 specification. A common jumbo
frame size is 9022 bytes.
With both of
these new technologies, the bounds on the size of a transmit operation is now
greatly beyond the 1522 bytes of a...
