4. Internal Switching Fabric > Packet Queuing
96
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
4.4.3.1
First Come, First Served Mode
In this mode, packets flow through the ingress queues in order unless reordering is required to manage
head-of-line blocking. The packet closest to the head of the queue that can make progress is selected to
make progress regardless of its priority.
Reordering of packets only occurs if the packet at the head of the queue is blocked and there is at least
one packet that can make progress. Reordering of packets does not occur if there is no other packets in
the buffer.
This input arbitration mode can produce the best throughput when prioritization of traffic is not
important.
4.4.3.2
Strict Priority One
In this mode, higher priority packets are served ahead of lower priority packets if the higher priority
packets are not blocked. Write the IN_ARB_MODE field in the
“Fabric Control Register” on page 380
to select this mode.
In this mode, reordering operations only occur when the head of the queue is blocked and there is a
packet request with a higher precedence (according to the rules in
which exists in the queue.
The arbiter selects a packet to compete in egress arbitration based on the following rules:
•
Select the priority 3 packet that can be accepted by its destination fabric port and is closest to the
head of the queue;
•
Else if there are no such packets, Select the priority 2 packet that can be accepted by its destination
fabric port and is closest to the head of the queue;
•
Else if there are no such packets, Select the priority 1 packet that can be accepted by its destination
fabric port and is closest to the head of the queue;
•
Else if there are no such packets, Select the priority 0 packet that can be accepted by its destination
fabric port and is closest to the head of the queue;
•
Else if there are no such packets, Select the priority 3 packet closest to the head of the queue; Note
that this packet cannot make progress.
•
Else if there are no such packets, Select the priority 2 packet closest to the head of the queue; Note
that this packet cannot make progress.
•
Else if there are no such packets, Select the priority 1 packet closest to the head of the queue; Note
that this packet cannot make progress.
•
Else if there are no such packets, Select the priority 0 packet closest to the head of the queue.Note
that this packet cannot make progress.
The reordering limit impacts which packet can be chosen (see
The reordering limit impacts which packet can be chosen (see
Содержание Tsi578
Страница 1: ...IDT Tsi578 Serial RapidIO Switch User Manual June 6 2016 Titl ...
Страница 20: ...About this Document 20 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 102: ...4 Internal Switching Fabric Packet Queuing 102 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 228: ...11 Signals Pinlist and Ballmap 228 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 504: ...B Clocking P_CLK Programming 504 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 526: ...Index 526 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...