Intel ARCHITECTURE IA-32 - Manual (Page 547)

E-1
E
Mathematics of Prefetch
Scheduling Distance
This appendix discusses how far away to insert prefetch instructions. It
presents a mathematical model allowing you to deduce a simplified
equation which you can use for determining the prefetch scheduling
distance (PSD) for your application.
For your convenience, the first section presents this simplified equation;
the second section provides the background for this equation: the
mathematical model of the calculation.
Simplified Equation
A simplified equation to compute PSD is as follows:
where
psd is prefetch scheduling distance.
Nlookup is the number of clocks for lookup latency. This
parameter is system-dependent. The type of memory
used and the chipset implementation affect its value.
Nxfer is the number of clocks to transfer a cache-line. This
parameter is implementation-dependent.
N
pref
and N
st
are the numbers of cache lines to be prefetched and
stored.
CPI is the number of clocks per instruction. This parameter
is implementation-dependent.
psd
Nlookup Nxfer N
pref
N
st
+
( ) ⋅
+
CPI N
inst
⋅
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