<s>
In	O
computing	O
,	O
memory	B-General_Concept
ballooning	I-General_Concept
is	O
a	O
technique	O
used	O
to	O
eliminate	O
the	O
need	O
to	O
overprovision	O
host	O
memory	O
used	O
by	O
a	O
virtual	B-Architecture
machine	I-Architecture
(	O
VM	O
)	O
.	O
</s>
<s>
To	O
implement	O
it	O
,	O
the	O
virtual	B-Architecture
machine	I-Architecture
's	O
kernel	O
implements	O
a	O
"	O
balloon	B-General_Concept
driver	I-General_Concept
"	O
which	O
allocates	O
unused	O
memory	O
within	O
the	O
VM	O
's	O
address	O
space	O
into	O
a	O
reserved	O
memory	O
pool	O
(	O
the	O
"	O
balloon	O
"	O
)	O
so	O
that	O
it	O
is	O
unavailable	O
to	O
other	O
processes	O
on	O
the	O
VM	O
.	O
</s>
<s>
However	O
,	O
rather	O
than	O
being	O
reserved	O
for	O
other	O
uses	O
within	O
the	O
VM	O
,	O
the	O
physical	O
memory	O
mapped	O
to	O
those	O
pages	O
within	O
the	O
VM	O
is	O
actually	O
unmapped	O
from	O
the	O
VM	O
by	O
the	O
host	O
operating	O
system	O
's	O
hypervisor	B-Operating_System
,	O
making	O
it	O
available	O
for	O
other	O
uses	O
by	O
the	O
host	B-Operating_System
machine	I-Operating_System
.	O
</s>
