Port buffer drop counters in SONiC

Requirements Document

Table of Contents

• List of Tables
• List of Figures
• Revision
• About this Manual
• Scope
• Defintions/Abbreviation
• 1 Overview
• 2 Requirements
  • 2.1 Functional Requirements
  • 2.2 Supported Counters
• 3 Design
  • 3.1 CLI (and usage example)

List of Tables

• Table 1: Abbreviations

Revision

About this Manual

This document provides an overview of requirements of port buffer drop counters in SONiC.

Scope

This document describes the motivation for port buffer drop counters and the changes expected.

Definitions/Abbreviation

1 Overview

The main goal of this feature is to poll port level buffer drop counters in a safe way. According to https://github.com/sonic-net/sonic-swss/pull/1308,

These counters are causing widespread issues in the master branch, so we're backing them out for now to be revisited in a later PR. They will likely need to be polled separately from the other counters, and on a longer interval, to avoid performance issues and conflicts.

The solution for now is to introduce a new FC group with a larger polling interval than the rest of port counters. Also limit user configuring a small interval for this FC group via CLI.

2 Requirements

2.1 Functional Requirements

1. New flex counter group is introduced for the port-level buffer drop counters
2. The FC group is enabled by default
3. The polling interval is 60s by default
4. Users can configure FC group via a CLI tool
   1. Users can enable/disable polling
   2. Users can set the polling interval in range from 30s to 5m
   3. Users can view the FC configuration

2.2 Supported Counters

• SAI_PORT_STAT_IN_DROPPED_PKTS: port-level ingress buffer drop counters
• SAI_PORT_STAT_OUT_DROPPED_PKTS: port-level egress buffer drop counters

3 Design

3.1 CLI (and usage example)

3.1.1 Displaying the FC configuration

Current imlemenation

admin@sonic:~$ counterpoll show
Type                        Interval (in ms)    Status
--------------------------  ------------------  --------
QUEUE_STAT                  default (10000)     enable
PORT_STAT                   default (1000)      enable
RIF_STAT                    default (1000)      enable
QUEUE_WATERMARK_STAT        default (10000)     enable
PG_WATERMARK_STAT           default (10000)     enable
BUFFER_POOL_WATERMARK_STAT  default (10000)     enable

New imlementation

admin@sonic:~$ counterpoll show
Type                        Interval (in ms)    Status
--------------------------  ------------------  --------
QUEUE_STAT                  default (10000)     enable
PORT_STAT                   default (1000)      enable
PORT_BUFFER_DROP            default (60000)     enable
RIF_STAT                    default (1000)      enable
QUEUE_WATERMARK_STAT        default (10000)     enable
PG_WATERMARK_STAT           default (10000)     enable
BUFFER_POOL_WATERMARK_STAT  default (10000)     enable

3.1.2 Enabling/Disabling the polling

admin@sonic:~$ counterpoll port-buffer-drop enable
admin@sonic:~$ counterpoll port-buffer-drop disable

3.1.3 Setting new polling interval

admin@sonic:~$ counterpoll port-buffer-drop interval 30000