<s>
Zoom	O
is	O
a	O
performance	O
analysis	O
tool	O
for	O
applications	O
running	O
on	O
the	O
Linux	B-Application
and	O
macOS	B-Application
operating	O
systems	O
from	O
RotateRight	O
.	O
</s>
<s>
Statistical	O
sampling	O
is	O
the	O
periodic	O
recording	O
of	O
a	O
processor	O
's	O
program	B-General_Concept
counter	I-General_Concept
or	O
instruction	B-General_Concept
pointer	I-General_Concept
.	O
</s>
<s>
Statistical	O
sampling	O
can	O
be	O
either	O
system-wide	O
or	O
target	O
a	O
specific	O
process	B-Operating_System
.	O
</s>
<s>
System-wide	O
sampling	O
captures	O
all	O
of	O
the	O
processes	O
running	O
on	O
a	O
system	O
,	O
and	O
can	O
include	O
time	O
spent	O
in	O
kernel	B-Operating_System
or	O
driver	O
code	O
as	O
well	O
.	O
</s>
<s>
Process-targeted	O
sampling	O
can	O
be	O
used	O
to	O
understand	O
time	O
spent	O
waiting	O
for	O
I/O	O
or	O
kernel	B-Operating_System
work	O
.	O
</s>
<s>
Additional	O
information	O
besides	O
the	O
program	B-General_Concept
counter	I-General_Concept
can	O
be	O
recorded	O
at	O
each	O
interval	O
.	O
</s>
<s>
For	O
example	O
,	O
other	O
Hardware	B-General_Concept
performance	I-General_Concept
counters	I-General_Concept
can	O
be	O
read	O
or	O
the	O
entire	O
function	O
call	B-General_Concept
stack	I-General_Concept
can	O
be	O
recorded	O
.	O
</s>
<s>
There	O
are	O
a	O
variety	O
of	O
methods	O
for	O
summarizing	O
the	O
information	O
in	O
a	O
set	O
of	O
samples	O
that	O
include	O
backtraces	B-Language
of	O
each	O
sample	O
's	O
call	B-General_Concept
stack	I-General_Concept
:	O
</s>
<s>
Top-down	O
(	O
tree	B-Application
)	O
visualization	O
is	O
used	O
to	O
find	O
"	O
hot	O
"	O
(	O
frequently	O
sampled	O
)	O
call	O
paths	O
,	O
starting	O
at	O
the	O
root	O
symbol	O
(	O
e.g.	O
</s>
<s>
Bottom-up	O
(	O
leaf	B-Data_Structure
)	O
visualization	O
is	O
used	O
to	O
find	O
"	O
hot	O
"	O
code	O
,	O
starting	O
in	O
the	O
symbols	O
where	O
samples	O
occurred	O
.	O
</s>
<s>
Hotspot	O
visualization	O
is	O
a	O
complete	O
list	O
of	O
symbols	O
encountered	O
in	O
the	O
profile	O
that	O
is	O
used	O
in	O
conjunction	O
with	O
a	O
side-by-side	O
tree	B-Application
and	O
leaf	B-Data_Structure
views	O
(	O
butterfly	O
view	O
)	O
.	O
</s>
<s>
This	O
is	O
the	O
same	O
information	O
used	O
by	O
debuggers	B-Application
such	O
as	O
gdb	B-Language
.	O
</s>
<s>
Displays	O
basic	B-Application
blocks	I-Application
.	O
</s>
<s>
Computes	O
register	B-General_Concept
dependencies	O
.	O
</s>
<s>
Finds	O
branch	B-General_Concept
targets	O
.	O
</s>
