<s>
Prefetching	B-General_Concept
in	O
computer	O
science	O
is	O
a	O
technique	O
for	O
speeding	O
up	O
fetch	O
operations	O
by	O
beginning	O
a	O
fetch	O
operation	O
whose	O
result	O
is	O
expected	O
to	O
be	O
needed	O
soon	O
.	O
</s>
<s>
Usually	O
this	O
is	O
before	O
it	O
is	O
known	O
to	O
be	O
needed	O
,	O
so	O
there	O
is	O
a	O
risk	O
of	O
wasting	O
time	O
by	O
prefetching	B-General_Concept
data	O
that	O
will	O
not	O
be	O
used	O
.	O
</s>
