<s>
Coscheduling	B-Operating_System
is	O
the	O
principle	O
for	O
concurrent	B-Operating_System
systems	I-Operating_System
of	O
scheduling	O
related	O
processes	B-Operating_System
to	O
run	O
on	O
different	O
processors	O
at	O
the	O
same	O
time	O
(	O
in	O
parallel	B-Operating_System
)	O
.	O
</s>
<s>
If	O
an	O
application	O
consists	O
of	O
a	O
collection	O
of	O
processes	B-Operating_System
working	O
closely	O
together	O
,	O
and	O
if	O
some	O
but	O
not	O
all	O
of	O
the	O
processes	B-Operating_System
are	O
scheduled	O
for	O
execution	O
,	O
the	O
executing	O
processes	B-Operating_System
may	O
attempt	O
to	O
communicate	O
with	O
those	O
that	O
are	O
not	O
executing	O
,	O
which	O
will	O
cause	O
them	O
to	O
block	O
.	O
</s>
<s>
Eventually	O
the	O
other	O
processes	B-Operating_System
will	O
be	O
scheduled	O
for	O
execution	O
,	O
but	O
by	O
this	O
time	O
the	O
situation	O
may	O
be	O
reversed	O
so	O
that	O
these	O
processes	B-Operating_System
also	O
block	O
waiting	O
for	O
interactions	O
with	O
others	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
application	O
makes	O
progress	O
at	O
the	O
rate	O
of	O
at	O
most	O
one	O
interprocess	B-Operating_System
interaction	I-Operating_System
per	O
time	O
slice	O
,	O
and	O
will	O
have	O
low	O
throughput	O
and	O
high	O
latency	O
.	O
</s>
<s>
Coscheduling	B-Operating_System
consists	O
of	O
two	O
ideas	O
:	O
</s>
<s>
When	O
scheduling	O
any	O
of	O
the	O
processes	B-Operating_System
in	O
the	O
related	O
group	O
,	O
schedule	O
all	O
of	O
them	O
for	O
execution	O
so	O
that	O
they	O
can	O
communicate	O
efficiently	O
.	O
</s>
<s>
Some	O
coscheduling	B-Operating_System
techniques	O
exhibit	O
fragments	O
of	O
processes	B-Operating_System
that	O
do	O
not	O
run	O
concurrently	O
with	O
the	O
rest	O
of	O
the	O
coscheduled	O
set	O
.	O
</s>
<s>
Gang	B-Operating_System
scheduling	I-Operating_System
is	O
a	O
stricter	O
variant	O
of	O
coscheduling	B-Operating_System
that	O
disallows	O
fragments	O
completely	O
.	O
</s>
<s>
Researchers	O
have	O
classified	O
three	O
types	O
of	O
coscheduling	B-Operating_System
:	O
explicit	O
coscheduling	B-Operating_System
,	O
local	O
scheduling	O
and	O
implicit	O
or	O
dynamic	O
coscheduling	B-Operating_System
.	O
</s>
<s>
Explicit	O
coscheduling	B-Operating_System
requires	O
all	O
processing	O
to	O
actually	O
take	O
place	O
at	O
the	O
same	O
time	O
,	O
and	O
is	O
typically	O
implemented	O
by	O
global	O
scheduling	O
across	O
all	O
processors	O
.	O
</s>
<s>
A	O
specific	O
algorithm	O
is	O
known	O
as	O
gang	B-Operating_System
scheduling	I-Operating_System
.	O
</s>
<s>
Local	O
coscheduling	B-Operating_System
allows	O
individual	O
processors	O
to	O
schedule	O
the	O
processing	O
independently	O
.	O
</s>
<s>
Dynamic	O
(	O
or	O
implicit	O
)	O
coscheduling	B-Operating_System
is	O
a	O
form	O
of	O
coscheduling	B-Operating_System
where	O
individual	O
processors	O
can	O
still	O
schedule	O
processing	O
independently	O
,	O
but	O
they	O
make	O
scheduling	O
decisions	O
in	O
cooperation	O
with	O
other	O
processors	O
.	O
</s>
<s>
The	O
term	O
"	O
coscheduling	B-Operating_System
"	O
was	O
introduced	O
by	O
.	O
</s>
<s>
The	O
original	O
definition	O
is	O
that	O
the	O
process	O
working	O
set	O
must	O
be	O
coscheduled	O
(	O
scheduled	O
for	O
execution	O
simultaneously	O
)	O
for	O
the	O
parallel	B-Operating_System
program	I-Operating_System
to	O
make	O
progress	O
.	O
</s>
