Intel® Arria® 10 Hard Processor System Technical Reference Manual

ID 683711
Date 1/10/2023
Public

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8.3.4.6.2. Example: Tuning for Specific Throughput Requirements

In this example, we require each master to meet specific throughput requirements.

Consider a system in which masters A, B, and C have the following throughput requirements:

  • Master A: 1000 MBps operating at 100 MHz
  • Master B: 800 MBps operating at 800 MHz
  • Master C: 500 MBps operating at 400 Mhz

We achieve this by using the QoS generators in regulator mode. There are other masters in the system, and these three masters may need to "steal" bandwidth from them to achieve the required throughputs. Therefore, all the other QoS generators are configured in limiter mode to cap their bandwidth usage.

To set up the QoS generators for masters A, B, and C, we can use the settings in the following table.

Table 66.  Regulator Example Settings
Master QoS Mode QoS Bandwidth QoS Saturation (register value) 18
A Regulator 2560 64 bytes (saturation = 4)
B Regulator 256 256 bytes (saturation = 16)
C Regulator 320 128 bytes (saturation = 8)

Not shown are the master urgencies. When a QoS regulator achieves the required bandwidth the urgency is downgraded to allow other masters to achieve their required bandwidth.

We also set the urgency threshold values, P1 and P0. P1 is the urgency when a master falls below the bandwidth threshold. P0 is the urgency when a master is above the bandwidth threshold. regulator mode ensures a minimum bandwidth to the master, by raising the urgency when the bandwidth falls below the threshold, and downgrading it when the bandwidth is back above the threshold.

For any master the value of P1 must be greater or equal than P0.

18 The QoS bandwidth register value is computed as (desired bandwidth (MBps) * 256) / master frequency (MHz)