Alcatel-Lucent 7210 SAS M OS Quality Of Service Manual page 63

weighting exponent used to determine the portion of the shared buffer instantaneous utilization
and the previous shared buffer average utilization used to calculate the new shared buffer average
utilization. To derive the new shared buffer average utilization, the buffer pool takes a portion of
the previous shared buffer average and adds it to the inverse portion of the instantaneous shared
buffer utilization (SBU). The formula used to calculated the average shared buffer utilization is:
where:
SBAU
SBAU
SBU = The instantaneous shared buffer utilization
TAF = The time average factor
Table 27
instantaneous SBU and the previous SBAU (SBAU
(SBAU
Table 26: TAF Impact on Shared Buffer Average Utilization Calculation
TAF
0
1
2
3
4
5
6
7
8
7210 SAS M OS Quality of Service Guide
⎛
=
SBAU SBU
⎝
n
= Shared buffer average utilization for event n
n
= Shared buffer average utilization for event (n-1)
n-1
shows the effect the allowed values of TAF have on the relative weighting of the
).
n
TAF Equates
2
To
1
0
2
2
1
2
4
2
2
8
3
2
16
4
2
5 32
2
64
6
2
128
7
2
256
8
2
⎛
1 2
⎞
× ----------- - × -------------------- -
⎜
+
SBAU
⎠
n 1
–
TAF ⎝
2
n-1)
Shared Buffer
Instantaneous
Utilization Portion
1/1 (1)
1/2 (0.5)
1/4 (0.25)
1/8 (0.125)
1/16 (0.0625)
1/32 (0.03125)
1/64 (0.015625)
1/128 (0.0078125)
1/256 (0.00390625)
⎞
TAF
1
–
⎟
TAF ⎠
2
has on the calculating the current SBAU
Shared Buffer Average
Utilization Portion
0 (0)
1/2 (0.5)
3/4 (0.75)
7/8 (0.875)
15/16 (0.9375)
31/32 (0.96875)
63/64 (0.984375)
127/128 (0.9921875)
255/256 (0.99609375)
QoS Policies
Page 63