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[Dynamic buffer] [Mellanox] Calculate the peer response time according to the speed #1930

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merged 2 commits into from
Nov 15, 2021
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[Dynamic buffer] [Mellanox] Calculate the peer response time according to the speed #1930

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e158584
calcaulate the peer response time according to the operating speed
keboliu Sep 13, 2021
0b48d48
fix review comments
keboliu Sep 13, 2021
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25 changes: 24 additions & 1 deletion cfgmgr/buffer_headroom_mellanox.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,23 @@ local state_db = "6"

local ret = {}

-- pause quanta should be taken for each operating speed is defined in IEEE 802.3 31B.3.7
-- the key of table pause_quanta_per_speed is operating speed at Mb/s
-- the value of table pause_quanta_per_speed is the number of pause_quanta
local pause_quanta_per_speed = {}
pause_quanta_per_speed[400000] = 905
pause_quanta_per_speed[200000] = 453
pause_quanta_per_speed[100000] = 394
pause_quanta_per_speed[50000] = 147
pause_quanta_per_speed[40000] = 118
pause_quanta_per_speed[25000] = 80
pause_quanta_per_speed[10000] = 67
pause_quanta_per_speed[1000] = 2
pause_quanta_per_speed[100] = 1

-- Get pause_quanta from the pause_quanta_per_speed table
local pause_quanta = pause_quanta_per_speed[port_speed]

if gearbox_delay == nil then
gearbox_delay = 0
end
Expand All @@ -55,7 +72,8 @@ for i = 1, #asic_table_content, 2 do
if asic_table_content[i] == "mac_phy_delay" then
mac_phy_delay = tonumber(asic_table_content[i+1]) * 1024
end
if asic_table_content[i] == "peer_response_time" then
-- If failed to get pause_quanta from the table, then use the default peer_response_time stored in state_db
if asic_table_content[i] == "peer_response_time" and pause_quanta == nil then
peer_response_time = tonumber(asic_table_content[i+1]) * 1024
end
end
Expand Down Expand Up @@ -124,6 +142,11 @@ else
bytes_on_gearbox = port_speed * gearbox_delay / (8 * 1024)
end

-- If successfully get pause_quanta from the table, then calculate peer_response_time from it
if pause_quanta ~= nil then
peer_response_time = (pause_quanta) * 512 / 8
end

bytes_on_cable = 2 * cable_length * port_speed * 1000000000 / speed_of_light / (8 * 1024)
propagation_delay = port_mtu + bytes_on_cable + 2 * bytes_on_gearbox + mac_phy_delay + peer_response_time

Expand Down