This document discusses debugging and profiling challenges with OpenCL and how AMD CodeXL addresses them. It provides an overview of CodeXL's debugging and profiling capabilities for OpenCL, including API-level debugging, kernel source debugging, profiling views for APIs, objects, and kernel variables, and integrated support in Visual Studio. Demo code is included to illustrate pinpointing OpenCL errors and optimizing work item loads.

1. ADVANCED
OPENCL™
DEBUGGING
AND
PROFILING
USING
CODEXL
BUDI
PURNOMO
URI
SHOMRONI
GNANABASKARAN
MUTHUMANI

2. ABOUT
OpenCL™
OpenCL™
is
FUN!
! Parallel
compute
programming
language
! Exposes
the
massively
mulPthreaded
GPU
! A
lot
of
horsepower,
opPmized
for
parallel
compuPng
! Order-­‐of-­‐magnitude
performance
improvement!
2
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

3. OpenCL™
DEBUGGING
AND
PROFILING
CHALLENGES
However,
! Debugging
and
profiling
parallel
processing
applicaPons
is
hard
! On-­‐Pme
delivery
of
robust
(bug-­‐free)
OpenCL™
applicaPons
is
challenging
! It
is
almost
impossible
to
opPmize
an
OpenCL™-­‐based
applicaPon
to
fully
uPlize
the
available
parallel
processing
system
resources
3
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

4. OpenCL™
DEBUGGING
AND
PROFILING
CHALLENGES
OpenCL™
is
a
“Black
Box”
! The
applicaPon
enqueues
OpenCL™
commands
!
The
OpenCL™
runPme
executes
the
commands
ApplicaPon
! Using
a
host
profiler
and
debugger,
the
developer
cannot
‒ Debug
and
profile
the
OpenCL™
kernels
‒ See
the
execuPon
details
‒ View
runPme
loads
OpenCL™
4
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

5. AMD
CodeXL
! APU
and
GPU
Debugging
FuncPonality
‒ OpenCL™
and
OpenGL
API-­‐Level
‒ OpenCL™
Kernel
Source
Code
! APU,
CPU
and
GPU
Profiling
! OpenCL™
StaPc
Kernel
Analysis
! Provides
the
informaPon
a
developer
needs
to
help
find
bugs
and
opPmize
the
applicaPon’s
performance
! Integrated
into
Microsoa®
Visual
Studio®
! Standalone
applicaPon
for
Windows®
and
Linux®
5
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

6. GPU
Debugging

7. GPU
DEBUGGING
WITH
AMD
CodeXL
|
DEMO
AMDTTEAPOT
! Sample
provided
with
CodeXL
tools
suite
‒ API-­‐Level
debugging
‒ PinpoinPng
OpenCL
™
Errors
‒ Entering
Kernel
debugging
‒ Locals
and
Watch
views
‒ Kernel
Source
breakpoints
‒ Finding
problemaPc
work
items
‒ OpenCL
™
Kernel
MulPwatch
view
7
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

8. GPU
DEBUGGING
WITH
AMD
CodeXL
|
VIEWS
API
CALLS
HISTORY
VIEW
! Displays
OpenCL
™
and
OpenGL
API
calls
‒ Supports
funcPon
calls
from
OpenCL™
up
to
version
1.2
and
OpenGL
up
to
version
4.3
‒ FuncPon
parameters
‒ Object
links
in
properPes
‒ API
calls
are
divided
per
Compute
/
Render
context.
‒ Calls
history
recording
to
an
HTML
log
file
8
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

9. GPU
DEBUGGING
WITH
AMD
CodeXL
|
VIEWS
CODEXL
EXPLORER
! Displays
OpenCL™
and
OpenGL
allocated
objects
calls
‒ Object
Hierarchy
and
counts
‒ Object
properPes
‒ For
objects
with
data
/
sources
-­‐
double
click
to
open
a
main
view
‒ Display
detected
memory
leaks
if
"Break
on
Memory
Leaks"
is
selected.
9
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

10. GPU
DEBUGGING
WITH
AMD
CodeXL
|
VIEWS
SOURCE
AND
CALL
STACK
VIEWS
! Displays
host
code,
OpenCL™
kernel
source,
and
OpenGL
shader
source
‒ Set
source-­‐level
breakpoints
in
OpenCL™
kernels
‒ Display
host
thread
and
OpenCL™
kernel
wavefront
call
stacks
‒ Visual
Studio®
integraPon
10
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

11. GPU
DEBUGGING
WITH
AMD
CodeXL
|
VIEWS
OBJECT
VIEWS
! Displays
image,
buffer
and
texture
data
‒ Image
view
for
OpenCL™
images
and
OpenGL
textures
and
render
buffers
‒ 3D
image
support
with
layer
selecPon
slider
‒ Non-­‐RGB
images
mapped
to
grayscale
range,
with
selecPon
of
minimum
and
maximum
values
clearly
displaying
out-­‐of-­‐range
values
‒ Data
view
for
all
objects
‒ Channel
order
/
type
selecPon
for
buffer
data
‒ ConnecPon
to
image
view
for
objects
that
support
it
11
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

12. GPU
DEBUGGING
WITH
AMD
CodeXL
|
VIEWS
LOCALS
AND
WATCH
VIEWS
! Display
OpenCL™
kernel
variables
‒ Structure
and
vector
types
support
‒ Global
and
Private
memory
array
dereferencing
‒ Local
and
Constant
memory
support
planned
for
future
releases
‒ Visual
Studio®
integraPon
12
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

13. GPU
DEBUGGING
WITH
AMD
CodeXL
|
VIEWS
MULTIWATCH
VIEWS
! Display
a
single
OpenCL™
kernel
variable
value
across
the
current
work
items
‒ Image
and
Data
visualizaPon
‒ Range
slider,
like
Object
image
view
‒ Current
work
item
is
highlighted
and
can
be
changed
by
double-­‐clicking
the
data
view.
13
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

14. GPU
DEBUGGING
WITH
AMD
CodeXL
|
FEATURES
NEW
IN
CODEXL
1.3
! Remote
debugging
‒ Debug
capabiliPes
on
a
remote
machine
‒ API-­‐level
debugging
‒ Kernel
debugging
‒ Requires
a
CodeXL
agent
running
on
the
target
machine
‒ The
agent
is
included
as
an
opPon
in
the
CodeXL
installer
‒ Same
agent
for
remote
GPU
debugging
and
remote
GPU
profiling
‒ Currently
only
supports
Windows-­‐to-­‐Windows
and
Linux-­‐to-­‐Linux
debugging
! OpenCL™
API
support
increased
up
to
OpenCL™
1.2
‒ New
API
funcPons
‒ New
deprecated
funcPons
and
behaviors
! OpenGL
API
support
increased
up
to
OpenGL
4.3
‒ New
API
funcPons
and
tokens
‒ New
shader
types
14
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

15. GPU
DEBUGGING
WITH
AMD
CodeXL
|
FEATURES
UPCOMING
RELEASES
! Hardware-­‐based
kernel
debugging
‒ Current
implementaPon
retrieves
hardware
values
but
performs
kernel
playback
for
breakpoint
implementaPon
‒ Display
data
for
the
enPre
grid
‒ OpPmized
for
small-­‐
and
medium-­‐sized
kernels
‒ Does
not
support
debugging
kernels
that
can't
be
replayed
consistently
(such
as
kernels
using
atomics)
‒ New
implementaPon
will
use
hardware
breakpoints
‒ Display
data
according
to
the
wavefronts
executed
in
the
actual
hardware
‒ Faster
for
large
kernels
‒ Stop
and
resume
wavefront
execuPon
‒ Can
break
a
running
kernel
‒ Can
support
debugging
persistent
kernels
(aoach
to
kernel)
‒ Will
allow
data
breakpoints
‒ Working
development
build
in
the
demo
area!
15
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

16. GPU
Profiling

17. GPU
PROFILING
WITH
AMD
CodeXL
KEY
FEATURES
! Analyze
and
profile
OpenCL™
host
and
device
code
‒ Collect
applicaPon
trace
mode
‒ Collect
GPU
performance
counter
mode
! Views:
‒ API
trace:
View
API
calls
with
inputs
and
outputs
‒ Timeline
visualizaPon:
View
host
and
device
synch
issue
‒ Summary
pages:
Find
top
booleneck
‒ Warnings/Errors:
View
performance
suggesPons
‒ Kernel
occupancy:
Find
kernel
resource
booleneck
‒ Performance
counter:
View
kernel
perf
booleneck
! Does
not
require
source
or
project
modificaPons
to
the
applicaPon
! Does
not
even
require
the
applicaPon
source
code
17
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

18. GPU
PROFILING
WITH
AMD
CodeXL
|
Views
API
TRACE
! Analyze
and
profile
OpenCL™
applicaPons
‒ View
API
input
arguments
and
output
results
‒ Find
API
hotspots
‒ Determine
top
ten
data
transfer
and
kernel
execuPon
operaPons
‒ IdenPfy
failed
API
calls,
resource
leaks
and
best
pracPces
18
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

19. GPU
PROFILING
WITH
AMD
CodeXL
|
Views
TIMELINE
VISUALIZATION
! Visualize
host
and
device
execuPon
in
a
Pmeline
chart
‒ View
number
of
OpenCL™
contexts
and
command
queues
created
and
the
relaPonships
between
these
items
‒ View
data
transfer
operaPons
and
kernel
execuPons
on
the
device
‒ Determine
proper
synchronizaPon
and
load
balancing
19
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

20. GPU
PROFILING
WITH
AMD
CodeXL
|
Views
SUMMARY
PAGES
! Find
top
boolenecks
‒ I/O
bound
‒ Compute
bound
20
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

21. GPU
PROFILING
WITH
AMD
CodeXL
|
Views
WARNING
AND
ERROR
MESSAGES
! Provide
performance
improvement
suggesPons
! Detect
errors
in
an
OpenCL™
applicaPon
21
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

22. GPU
PROFILING
WITH
AMD
CodeXL
|
Views
PERFORMANCE
COUNTER
! Analyze
the
OpenCL™
kernel
execuPon
for
AMD
APUs
and
GPUs
‒ Collect
GPU
Performance
Counters
‒ The
number
of
ALU,
global
and
local
memory
instrucPons
executed
‒ GPU
uPlizaPon
and
memory
access
characterisPcs
‒ Show
the
kernel
resource
usages
‒ View
the
AMD
intermediate
language
(AMD
IL)
and
hardware
disassembly
(ISA)
22
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

23. GPU
PROFILING
WITH
AMD
CodeXL
|
Views
KERNEL
OCCUPANCY
! EsPmate
OpenCL™
kernel
occupancy
for
AMD
APUs
and
GPUs
‒ Visual
indicaPon
of
the
limiPng
kernel
resources
for
number
of
wavefronts
in
flight
‒ View
the
maximum
number
of
wavefronts
in
flight
limited
by
‒ Work
group
size
‒ Number
of
allocated
scalar
or
vector
registers
‒ Amount
of
allocated
LDS
‒ View
the
maximum
resource
limit
for
the
GPU
device
23
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

24. GPU
PROFILING
WITH
AMD
CodeXL
|
DEMO
OpPmizing
AMD
teapot
applicaPon
! Finding
and
fixing
non-­‐opPmized
kernel
launch
parameters
‒ API
Trace
and
Warning
and
Error
Messages
View
! Visualizing
host
device
synchronizaPon
‒ Timeline
VisualizaPon
! NavigaPng
to
find
the
top
booleneck
‒ Summary
Pages
View
! OpPmizing
the
kernel
‒ Kernel
Occupancy
and
GPU
Performance
Counter
View
24
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

25. StaPc
Kernel
Analysis

26. STATIC
KERNEL
ANALYSIS
WITH
AMD
CodeXL
KEY
FEATURES
! Compile,
analyze
and
disassemble
an
OpenCL™
kernel
for
AMD
APUs,
GPUs
and
CPUs.
‒ View
AMD
IL
and
hardware
disassembly
(ISA)
‒ View
compilaPon
warning
and
error
messages
! Generate
offline
compilaPon
of
OpenCL™
kernel
binary
! View
compiler
staPsPcs
and
esPmate
performance
! Only
require
the
OpenCL™
kernel
source
code
as
an
input
! Does
not
require
a
GPU
in
the
system
26
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

27. STATIC
KERNEL
ANALYSIS
WITH
AMD
CodeXL
|
FEATURES
NEW
IN
CODEXL
1.3
! Integrated
into
AMD
CodeXL
standalone
and
Visual
Studio®
extension
! Brand
new
user
experience
‒ View
OpenCL™
kernel
source,
IL
and
ISA
simultaneously
‒ View
overview
‒ Generate
analysis
for
SI
and
CI
families
of
GPUs
‒ EsPmated
cycle
count
with
isa
branch
execuPon
classificaPon
‒ Navigate
compilaPon
and
analysis
results
in
tree
view
! Support
compilaPon
for
the
latest
AMD
APUs,
GPUs
and
CPUs
27
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

28. CPU
Profiling

29. CPU
PROFILING
WITH
AMD
CodeXL
! IdenPfy
and
invesPgate
CPU
performance
hot-­‐spots
! Profiles
C,
C++,
FORTRAN,
Java,
.NET,
OpenCL™
applicaPons
! Profiles
soaware
components
‒ ApplicaPons,
Libraries,
Dynamically
loaded
modules
‒ OS
Kernel
modules
! Profile
modes
‒ Per
Process
(target
applicaPon
and
its
children)
‒ System
Wide
Profiling
! Uses
HW
Performance
Monitoring
counters
‒ Low
overhead
! No
change
to
source
code
required
‒ Symbolic
informaPon
required
to
aoribute
the
performance
data
at
funcPon/source
level
29
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

30. CPU
PROFILING
WITH
AMD
CodeXL
! Profiling
Types
‒ Time-­‐based
profiling
‒ Event-­‐based
profiling
‒ InstrucPon
Based
Sampling
(IBS)
‒ Cache
Line
UPlizaPon
‒ Call
Graph
! Pre-­‐defined
profile
configuraPon
of
HW
performance
events
‒ Assess
Performance
‒ InvesPgate
Data
Access
‒ InvesPgate
Branching
30
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

31. CPU
PROFILING
WITH
AMD
CodeXL
! Performance
data
are
displayed
in
configurable
views
‒ Samples
aoributed
at
Process
and
Modules
level
‒ Drill
down
to
FuncPons,
Source
code
and
InstrucPons
level
31
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

32. CPU
PROFILING
WITH
AMD
CodeXL
! Call
Graph
view
displays
the
parents
and
children
of
hooest
funcPon
calls
32
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

33. CPU
PROFILING
WITH
AMD
CodeXL
! IdenPfy
Hotspots
‒ Where
the
applicaPon
spends
its
Pme
‒ Source
level/algorithm
related
performance
issues
‒ Use
Time-­‐base
profiling
! IdenPfy
the
cause
‒ How
well
the
applicaPon
is
using
the
CPU
and
Memory
resources
‒ Performance
boolenecks
due
to
the
micro-­‐architectural
constraints
‒ Use
Event-­‐based
profiling
or
InstrucPon
Based
Sampling
! Precise
instrucPon
level
profiling
‒ Use
InstrucPon
Based
Sampling
! Cache-­‐Line
UPlizaPon
-­‐
Data
access
paoern
33
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

34. CPU
Profiling
Demo

35. AMD
CodeXL
SUMMARY
! Powerful
APU
and
GPU
Debugging
‒ OpenCL™
API
Level
‒ OpenCL™
Kernel
Source
Code
! APU/GPU
and
CPU
Profiling
‒ IdenPfy
“hot
spots”
with
inefficient
code
! StaPc
Kernel
Analysis
‒ Compile,
analyze
and
disassemble
OpenCL™
kernel
‒ Generate
offline
compilaPon
of
OpenCL™
kernel
binary
! Integrated
into
Microsoa®
Visual
Studio®
! Standalone
applicaPon
for
Windows®
and
Linux®
! Free
download
at
hop://developer.amd.com
35
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013

36. Thank
you!
QuesPons?
Contact
us:
! Budi.Purnomo@amd.com
! Uri.Shomroni@amd.com
! Gnanabaskaran.Muthumani@amd.com

37. DISCLAIMER
&
ATTRIBUTION
The
informaPon
presented
in
this
document
is
for
informaPonal
purposes
only
and
may
contain
technical
inaccuracies,
omissions
and
typographical
errors.
The
informaPon
contained
herein
is
subject
to
change
and
may
be
rendered
inaccurate
for
many
reasons,
including
but
not
limited
to
product
and
roadmap
changes,
component
and
motherboard
version
changes,
new
model
and/or
product
releases,
product
differences
between
differing
manufacturers,
soaware
changes,
BIOS
flashes,
firmware
upgrades,
or
the
like.
AMD
assumes
no
obligaPon
to
update
or
otherwise
correct
or
revise
this
informaPon.
However,
AMD
reserves
the
right
to
revise
this
informaPon
and
to
make
changes
from
Pme
to
Pme
to
the
content
hereof
without
obligaPon
of
AMD
to
noPfy
any
person
of
such
revisions
or
changes.
AMD
MAKES
NO
REPRESENTATIONS
OR
WARRANTIES
WITH
RESPECT
TO
THE
CONTENTS
HEREOF
AND
ASSUMES
NO
RESPONSIBILITY
FOR
ANY
INACCURACIES,
ERRORS
OR
OMISSIONS
THAT
MAY
APPEAR
IN
THIS
INFORMATION.
AMD
SPECIFICALLY
DISCLAIMS
ANY
IMPLIED
WARRANTIES
OF
MERCHANTABILITY
OR
FITNESS
FOR
ANY
PARTICULAR
PURPOSE.
IN
NO
EVENT
WILL
AMD
BE
LIABLE
TO
ANY
PERSON
FOR
ANY
DIRECT,
INDIRECT,
SPECIAL
OR
OTHER
CONSEQUENTIAL
DAMAGES
ARISING
FROM
THE
USE
OF
ANY
INFORMATION
CONTAINED
HEREIN,
EVEN
IF
AMD
IS
EXPRESSLY
ADVISED
OF
THE
POSSIBILITY
OF
SUCH
DAMAGES.
ATTRIBUTION
©
2013
Advanced
Micro
Devices,
Inc.
All
rights
reserved.
AMD,
the
AMD
Arrow
logo,
the
AMD
Radeon
and
combinaPons
thereof
are
trademarks
of
Advanced
Micro
Devices,
Inc.
in
the
United
States
and/or
other
jurisdicPons.
OpenCL
is
a
trademark
of
Apple
Inc.
Microsoa,
Windows
and
Visual
Studio
are
trademarks
of
Microsoa
Corp.
Linux
is
a
trademark
of
Linus
Torvalds.
Other
names
are
for
informaPonal
purposes
only
and
may
be
trademarks
of
their
respecPve
owners.
37
|
ADVANCED
OPENCLTM
DEBUGGING
AND
PROFILING
USING
CODEXL
|
NOVEMBER
13,
2013