blob: d31619ad57cf2564f1a3b2c6fc831b2b28759f14 [file] [log] [blame]
Name
EXT_disjoint_timer_query
Name Strings
GL_EXT_disjoint_timer_query
Contact
Maurice Ribble, Qualcomm (mribble 'at' qualcomm.com)
Contributors
Matt Trusten
Maurice Ribble
Daniel Koch
Jan-Harald Fredriksen
Contributors to ANGLE_timer_query
Contributors to ARB_timer_query
Contributors to EXT_timer_query
Contributors to EXT_occlusion_query_boolean
This extension is based on the ARB_timer_query and ANGLE_timer_query
IP Status
No known IP claims.
Status
Complete
Version
Version 9, November 20, 2020
Number
OpenGL ES Extension #150
Dependencies
OpenGL ES 2.0 or greater required.
The extension is written against the OpenGL ES 2.0 specification.
The GetInteger64vEXT command is required only if OpenGL ES 3.0 or
later is not supported (see the Interactions section for details).
Overview
Applications can benefit from accurate timing information in a number of
different ways. During application development, timing information can
help identify application or driver bottlenecks. At run time,
applications can use timing information to dynamically adjust the amount
of detail in a scene to achieve constant frame rates. OpenGL
implementations have historically provided little to no useful timing
information. Applications can get some idea of timing by reading timers
on the CPU, but these timers are not synchronized with the graphics
rendering pipeline. Reading a CPU timer does not guarantee the completion
of a potentially large amount of graphics work accumulated before the
timer is read, and will thus produce wildly inaccurate results.
glFinish() can be used to determine when previous rendering commands have
been completed, but will idle the graphics pipeline and adversely affect
application performance.
This extension provides a query mechanism that can be used to determine
the amount of time it takes to fully complete a set of GL commands, and
without stalling the rendering pipeline. It uses the query object
mechanisms first introduced in the occlusion query extension, which allow
time intervals to be polled asynchronously by the application.
New Procedures and Functions
void GenQueriesEXT(sizei n, uint *ids);
void DeleteQueriesEXT(sizei n, const uint *ids);
boolean IsQueryEXT(uint id);
void BeginQueryEXT(enum target, uint id);
void EndQueryEXT(enum target);
void QueryCounterEXT(uint id, enum target);
void GetQueryivEXT(enum target, enum pname, int *params);
void GetQueryObjectivEXT(uint id, enum pname, int *params);
void GetQueryObjectuivEXT(uint id, enum pname, uint *params);
void GetQueryObjecti64vEXT(uint id, enum pname, int64 *params);
void GetQueryObjectui64vEXT(uint id, enum pname, uint64 *params);
void GetInteger64vEXT(enum pname, int64 *data)
New Tokens
Accepted by the <pname> parameter of GetQueryivEXT:
QUERY_COUNTER_BITS_EXT 0x8864
CURRENT_QUERY_EXT 0x8865
Accepted by the <pname> parameter of GetQueryObjectivEXT,
GetQueryObjectuivEXT, GetQueryObjecti64vEXT, and
GetQueryObjectui64vEXT:
QUERY_RESULT_EXT 0x8866
QUERY_RESULT_AVAILABLE_EXT 0x8867
Accepted by the <target> parameter of BeginQueryEXT, EndQueryEXT, and
GetQueryivEXT:
TIME_ELAPSED_EXT 0x88BF
Accepted by the <target> parameter of GetQueryiv and QueryCounter.
Accepted by the <value> parameter of GetBooleanv, GetIntegerv,
GetInteger64v, and GetFloatv:
TIMESTAMP_EXT 0x8E28
Accepted by the <value> parameter of GetBooleanv, GetIntegerv,
GetInteger64v, and GetFloatv:
GPU_DISJOINT_EXT 0x8FBB
Additions to Chapter 2 of the OpenGL ES 2.0 Specification (OpenGL ES Operation)
(Modify table 2.1, Correspondence of command suffix letters to GL argument)
Add two new types:
Letter Corresponding GL Type
------ ---------------------
i64 int64
ui64 uint64
(Modify table 2.2, GL data types) Add two new types:
GL Type Minimum Bit Width Description
------- ----------------- -----------------------------
int64 64 Signed 2's complement integer
uint64 64 Unsigned binary integer
Additions to Chapter 5 of the OpenGL ES 2.0 Specification (Special Functions)
Add a new section 5.3 "Timer Queries":
"5.3 Timer Queries
Timer queries use query objects to track the amount of time needed to
fully complete a set of GL commands, or to determine the current time
of the GL.
Timer queries are associated with query objects. The command
void GenQueriesEXT(sizei n, uint *ids);
returns <n> previously unused query object names in <ids>. These
names are marked as used, but no object is associated with them until
the first time they are used by BeginQueryEXT or QueryCounterEXT. Query
objects contain one piece of state, an integer result value. This result
value is initialized to zero when the object is created. Any positive
integer except for zero (which is reserved for the GL) is a valid query
object name.
Query objects are deleted by calling
void DeleteQueriesEXT(sizei n, const uint *ids);
<ids> contains <n> names of query objects to be deleted. After a
query object is deleted, its name is again unused. Unused names in
<ids> are silently ignored.
If an active query object is deleted its name immediately becomes unused,
but the underlying object is not deleted until it is no longer active.
A timer query can be started and finished by calling
void BeginQueryEXT(enum target, uint id);
void EndQueryEXT(enum target);
where <target> is TIME_ELAPSED_EXT. If BeginQueryEXT is called
with an unused <id>, that name is marked as used and associated with
a new query object.
If BeginQueryEXT is called with an <id> of zero, if the active query
object name for <target> is non-zero, if <id> is the name of an existing
query object whose type does not match <target>, or if <id> is the active
query object name for any query type, the error INVALID_OPERATION is
generated. If EndQueryEXT is called while no query with the same target
is in progress, an INVALID_OPERATION error is generated.
When BeginQueryEXT and EndQueryEXT are called with a <target> of
TIME_ELAPSED_EXT, the GL prepares to start and stop the timer used for
timer queries. The timer is started or stopped when the effects from all
previous commands on the GL client and server state and the framebuffer
have been fully realized. On some architectures framebuffer can have
different meanings (specifically on some tiling GPUs fully realized might refer
to the framebuffer being in tile memory before it gets copied out to system
memory). The BeginQueryEXT and EndQueryEXT commands may return before the
timer is actually started or stopped. When the timer query timer is finally
stopped, the elapsed time (in nanoseconds) is written to the corresponding
query object as the query result value, and the query result for that object
is marked as available.
If the elapsed time overflows the number of bits, <n>, available to hold
elapsed time, its value becomes undefined. It is recommended, but not
required, that implementations handle this overflow case by saturating at
2^n - 1.
The necessary state is a single bit indicating whether a timer
query is active, the identifier of the currently active timer
query, and a counter keeping track of the time that has passed.
When the command
void QueryCounterEXT(uint id, enum target);
is called with <target> TIMESTAMP_EXT, the GL records the current time
into the corresponding query object. The time is recorded after all
previous commands on the GL client and server state and the framebuffer
have been fully realized. On some architectures framebuffer can have
different meanings (specifically on some tiling GPUs fully realized might refer
to the framebuffer being in tile memory before it gets copied out to system
memory). When the time is recorded, the query result for that object is
marked available. QueryCounterEXT timer queries can be used within a
BeginQueryEXT / EndQueryEXT block where the <target> is TIME_ELAPSED_EXT and
it does not affect the result of that query object. The error
INVALID_OPERATION is generated if the <id> is already in use within a
BeginQueryEXT/EndQueryEXT block.
The current time of the GL may be queried by calling GetIntegerv or
GetInteger64v with the symbolic constant TIMESTAMP_EXT. This will return
the GL time after all previous commands have reached the GL server but have
not yet necessarily executed. By using a combination of this synchronous
get command and the asynchronous timestamp query object target,
applications can measure the latency between when commands reach the GL
server and when they are realized in the framebuffer.
In order to know if the value returned from GetIntegerv or GetQuery is valid
GPU_DISJOINT_EXT needs to be used to make sure the GPU did not perform any
disjoint operation. This can be done through GetIntegerv by using GPU_-
DISJOINT_EXT for <pname>. <params> will be filled with a non-zero value if
a disjoint operation occurred since the last time GetIntegerv was used with
GPU_DISJOINT_EXT. A zero value will be returned if no disjoint operation
occurred, indicating the values returned by this extension that are found
in-between subsequent GetIntegerv calls will be valid for performance
metrics.
Disjoint operations occur whenever a change in the GPU occurs that will
make the values returned by this extension unusable for performance
metrics. An example can be seen with how mobile GPUs need to proactively
try to conserve power, which might cause the GPU to go to sleep at the
lower levers. This means disjoint states will occur at different times on
different platforms and are implementation dependent. When the returned
value is non-zero, all time values that were filled since the previous
disjoint check should be considered undefined."
Additions to Chapter 6 of the OpenGL ES 2.0 Specification (State and State
Requests)
Add GetInteger64vEXT to section 6.1.1 "Simple Queries", following
the prototype for GetIntegerv:
" void GetInteger64vEXT(enum pname, int64 *data);
void GetFloatv(enum value, float *data);
The commands obtain boolean, integer, 64-bit integer, or floating-point
variables..."
Add a new section 6.1.9 "Timer Queries":
"The command
boolean IsQueryEXT(uint id);
returns TRUE if <id> is the name of a query object. If <id> is zero,
or if <id> is a non-zero value that is not the name of a query
object, IsQueryEXT returns FALSE.
Information about a query target can be queried with the command
void GetQueryivEXT(enum target, enum pname, int *params);
<target> identifies the query target and can be TIME_ELAPSED_EXT or
TIMESTAMP_EXT for timer queries.
If <pname> is CURRENT_QUERY_EXT, the name of the currently active query
for <target>, or zero if no query is active, will be placed in <params>.
If <pname> is QUERY_COUNTER_BITS_EXT, the implementation-dependent number
of bits used to hold the query result for <target> will be placed in
<params>. The number of query counter bits may be zero, in which case
the counter contains no useful information.
For timer queries (TIME_ELAPSED_EXT and TIMESTAMP_EXT), if the number
of bits is non-zero, the minimum number of bits allowed is 30 which
will allow at least 1 second of timing.
The state of a query object can be queried with the commands
void GetQueryObjectivEXT(uint id, enum pname, int *params);
void GetQueryObjectuivEXT(uint id, enum pname, uint *params);
void GetQueryObjecti64vEXT(uint id, enum pname, int64 *params);
void GetQueryObjectui64vEXT(uint id, enum pname, uint64 *params);
If <id> is not the name of a query object, or if the query object
named by <id> is currently active, then an INVALID_OPERATION error is
generated.
If <pname> is QUERY_RESULT_EXT, then the query object's result
value is returned as a single integer in <params>. If the value is so
large in magnitude that it cannot be represented with the requested type,
then the nearest value representable using the requested type is
returned. If the number of query counter bits for target is zero, then
the result is returned as a single integer with the value zero.
There may be an indeterminate delay before the above query returns. If
<pname> is QUERY_RESULT_AVAILABLE_EXT, FALSE is returned if such a delay
would be required; otherwise TRUE is returned. It must always be true
that if any query object returns a result available of TRUE, all queries
of the same type issued prior to that query must also return TRUE.
Querying the state for a given timer query forces that timer query to
complete within a finite amount of time.
If multiple queries are issued on the same target and id prior to
calling GetQueryObject[u]i[64]vEXT, the result returned will always be
from the last query issued. The results from any queries before the
last one will be lost if the results are not retrieved before starting
a new query on the same <target> and <id>.
Errors
The error INVALID_VALUE is generated if GenQueriesEXT is called where
<n> is negative.
The error INVALID_VALUE is generated if DeleteQueriesEXT is called
where <n> is negative.
The error INVALID_OPERATION is generated if BeginQueryEXT is called
when a query of the given <target> is already active.
The error INVALID_OPERATION is generated if EndQueryEXT is called
when a query of the given <target> is not active.
The error INVALID_OPERATION is generated if BeginQueryEXT is called
where <id> is zero.
The error INVALID_OPERATION is generated if BeginQueryEXT is called
where <id> is the name of a query currently in progress.
The error INVALID_OPERATION is generated if BeginQueryEXT is called
where <id> is the name of an existing query object whose type does not
match <target>.
The error INVALID_ENUM is generated if BeginQueryEXT or EndQueryEXT
is called where <target> is not TIME_ELAPSED_EXT.
The error INVALID_ENUM is generated if GetQueryivEXT is called where
<target> is not TIME_ELAPSED_EXT or TIMESTAMP_EXT.
The error INVALID_ENUM is generated if GetQueryivEXT is called where
<pname> is not QUERY_COUNTER_BITS_EXT or CURRENT_QUERY_EXT.
The error INVALID_ENUM is generated if QueryCounterEXT is called where
<target> is not TIMESTAMP_EXT.
The error INVALID_OPERATION is generated if QueryCounterEXT is called
on a query object that is already in use inside a
BeginQueryEXT/EndQueryEXT.
The error INVALID_OPERATION is generated if GetQueryObjectivEXT,
GetQueryObjectuivEXT, GetQueryObjecti64vEXT, or
GetQueryObjectui64vEXT is called where <id> is not the name of a query
object.
The error INVALID_OPERATION is generated if GetQueryObjectivEXT,
GetQueryObjectuivEXT, GetQueryObjecti64vEXT, or
GetQueryObjectui64vEXT is called where <id> is the name of a currently
active query object.
The error INVALID_ENUM is generated if GetQueryObjectivEXT,
GetQueryObjectuivEXT, GetQueryObjecti64vEXT, or
GetQueryObjectui64vEXT is called where <pname> is not
QUERY_RESULT_EXT or QUERY_RESULT_AVAILABLE_EXT.
New State
(Add a new table 6.xx, "Query Operations")
Get Value Type Get Command Initial Value Description Sec
--------- ---- ----------- ------------- ----------- ------
- B - FALSE query active 5.3
CURRENT_QUERY_EXT Z+ GetQueryivEXT 0 active query ID 5.3
QUERY_RESULT_EXT Z+ GetQueryObjectuivEXT, 0 samples-passed count 5.3
GetQueryObjectui64vEXT
QUERY_RESULT_AVAILABLE_EXT B GetQueryObjectivEXT FALSE query result available 5.3
New Implementation Dependent State
(Add the following entry to table 6.18):
Get Value Type Get Command Minimum Value Description Sec
-------------------------- ---- ----------- ------------- ---------------- ------
QUERY_COUNTER_BITS_EXT Z+ GetQueryivEXT see 6.1.9 Number of bits in 6.1.9
query counter
Interactions with OpenGL ES 2.0 and OpenGL ES 3.x
If only OpenGL ES 2.0 is supported, then GetInteger64vEXT is defined,
and is used instead of the GetInteger64v command defined by OpenGL ES
3.x. If OpenGL ES 3.0 or later is supported, GetInteger64vEXT is not
required by an implementation of this extension, and the changes to
section 6.1.1 are ignored.
Examples
(1) Here is some rough sample code that demonstrates the intended usage
of this extension.
GLint queries[N];
GLint available = 0;
GLint disjointOccurred = 0;
/* Timer queries can contain more than 32 bits of data, so always
query them using the 64 bit types to avoid overflow */
GLuint64 timeElapsed = 0;
/* Create a query object. */
glGenQueries(N, queries);
/* Clear disjoint error */
glGetIntegerv(GL_GPU_DISJOINT_EXT, &disjointOccurred);
/* Start query 1 */
glBeginQuery(GL_TIME_ELAPSED_EXT, queries[0]);
/* Draw object 1 */
....
/* End query 1 */
glEndQuery(GL_TIME_ELAPSED_EXT);
...
/* Start query N */
glBeginQuery(GL_TIME_ELAPSED_EXT, queries[N-1]);
/* Draw object N */
....
/* End query N */
glEndQuery(GL_TIME_ELAPSED_EXT);
/* Wait for all results to become available */
while (!available) {
glGetQueryObjectiv(queries[N-1], GL_QUERY_RESULT_AVAILABLE, &available);
}
/* Check for disjoint operation for all queries within the last
disjoint check. This way we can only check disjoint once for all
queries between, and once the last is filled we know all previous
will have been filled as well */
glGetIntegerv(GL_GPU_DISJOINT_EXT, &disjointOccurred);
/* If a disjoint operation occurred, all timer queries in between
the last two disjoint checks that were filled are invalid, continue
without reading the the values */
if (!disjointOccurred) {
for (i = 0; i < N; i++) {
/* See how much time the rendering of object i took in nanoseconds. */
glGetQueryObjectui64vEXT(queries[i], GL_QUERY_RESULT, &timeElapsed);
/* Do something useful with the time if a disjoint operation did
not occur. Note that care should be taken to use all
significant bits of the result, not just the least significant
32 bits. */
AdjustObjectLODBasedOnDrawTime(i, timeElapsed);
}
}
This example is sub-optimal in that it stalls at the end of every
frame to wait for query results. Ideally, the collection of results
would be delayed one frame to minimize the amount of time spent
waiting for the GPU to finish rendering.
(2) This example uses QueryCounter.
GLint queries[2];
GLint available = 0;
GLint disjointOccurred = 0;
/* Timer queries can contain more than 32 bits of data, so always
query them using the 64 bit types to avoid overflow */
GLuint64 timeStart, timeEnd, timeElapsed = 0;
/* Create a query object. */
glGenQueries(2, queries);
/* Clear disjoint error */
glGetIntegerv(GL_GPU_DISJOINT_EXT, &disjointOccurred);
/* Query current timestamp before drawing */
glQueryCounterEXT(queries[0], GL_TIMESTAMP_EXT);
/* Draw full rendertarget of objects */
/* Query current timestamp after drawing */
glQueryCounterEXT(queries[1], GL_TIMESTAMP_EXT);
/* Do some other work so you don't stall waiting for available */
/* Wait for the query result to become available */
while (!available) {
glGetQueryObjectiv(queries[1], GL_QUERY_RESULT_AVAILABLE, &available);
}
/* Check for disjoint operation. */
glGetIntegerv(GL_GPU_DISJOINT_EXT, &disjointOccurred);
/* If a disjoint operation occurred, continue without reading the the
values */
if (!disjointOccurred) {
/* Get timestamp for when rendertarget started. */
glGetQueryObjectui64vEXT(queries[0], GL_QUERY_RESULT, &timeStart);
/* Get timestamp for when rendertarget finished. */
glGetQueryObjectui64vEXT(queries[1], GL_QUERY_RESULT, &timeEnd);
/* See how much time the rendering took in nanoseconds. */
timeElapsed = timeEnd - timeStart;
/* Do something useful with the time if a disjoint operation did
not occur. Note that care should be taken to use all
significant bits of the result, not just the least significant
32 bits. */
AdjustObjectLODBasedOnDrawTime(timeElapsed);
}
(3) This example demonstrates how to measure the latency between GL
commands reaching the server and being realized in the framebuffer.
/* Submit a frame of rendering commands */
while (!doneRendering) {
...
glDrawElements(...);
}
/* Measure rendering latency:
Some commands may have already been submitted to hardware,
and some of those may have already completed. The goal is
to measure the time it takes for the remaining commands to
complete, thereby measuring how far behind the app the GPU
is lagging, but without synchronizing the GPU with the CPU. */
/* Clear disjoint error */
glGetIntegerv(GL_GPU_DISJOINT_EXT, &disjointOccurred);
/* Queue a query to find out when the frame finishes on the GL */
glQueryCounterEXT(endFrameQuery, GL_TIMESTAMP_EXT);
/* Get the current GL time without stalling the GL */
glGetIntegerv(GL_TIMESTAMP_EXT, &flushTime);
/* Finish the frame, submitting outstanding commands to the GL */
SwapBuffers();
/* Render another frame */
/* Later, compare the query result of <endFrameQuery>
and <flushTime> to measure the latency of the frame.
A disjoint error still needs to be checked for in order
to verify these values are valid. */
Issues from EXT_timer_query
(1) What time interval is being measured?
RESOLVED: The timer starts when all commands prior to BeginQueryEXT() have
been fully executed. At that point, everything that should be drawn by
those commands has been written to the framebuffer. The timer stops
when all commands prior to EndQueryEXT() have been fully executed.
(2) What unit of time will time intervals be returned in?
RESOLVED: Nanoseconds (10^-9 seconds). This unit of measurement allows
for reasonably accurate timing of even small blocks of rendering
commands. The granularity of the timer is implementation-dependent. A
32-bit query counter can express intervals of up to approximately 4
seconds.
(3) What should be the minimum number of counter bits for timer queries?
RESOLVED: 30 bits, which will allow timing sections that take up to 1
second to render.
(4) How are counter results of more than 32 bits returned?
RESOLVED: Via two new datatypes, int64 and uint64, and their
corresponding GetQueryObject entry points. These types hold integer
values and have a minimum bit width of 64.
(5) Should the extension measure total time elapsed between the full
completion of the BeginQuery and EndQuery commands, or just time
spent in the graphics library?
RESOLVED: This extension will measure the total time elapsed between
the full completion of these commands. Future extensions may implement
a query to determine time elapsed at different stages of the graphics
pipeline.
(6) If multiple query types are supported, can multiple query types be
active simultaneously?
RESOLVED: Yes; an application may perform a timer query and another
type of query simultaneously. An application can not perform multiple
timer queries or multiple queries of other types simultaneously. An
application also can not use the same query object for another query
and a timer query simultaneously.
(7) Do query objects have a query type permanently associated with them?
RESOLVED: No. A single query object can be used to perform different
types of queries, but not at the same time.
Having a fixed type for each query object simplifies some aspects of the
implementation -- not having to deal with queries with different result
sizes, for example. It would also mean that BeginQuery() with a query
object of the "wrong" type would result in an INVALID_OPERATION error.
UPDATE: This resolution was relevant for EXT_timer_query and OpenGL 2.0.
Since EXT_transform_feedback has since been incorporated into the core,
the resolution is that BeginQuery will generate error INVALID_OPERATION
if <id> represents a query object of a different type.
(8) How predictable/repeatable are the results returned by the timer
query?
RESOLVED: In general, the amount of time needed to render the same
primitives should be fairly constant. But there may be many other
system issues (e.g., context switching on the CPU and GPU, virtual
memory page faults, memory cache behavior on the CPU and GPU) that can
cause times to vary wildly.
Note that modern GPUs are generally highly pipelined, and may be
processing different primitives in different pipeline stages
simultaneously. In this extension, the timers start and stop when the
BeginQuery/EndQuery commands reach the bottom of the rendering pipeline.
What that means is that by the time the timer starts, the GL driver on
the CPU may have started work on GL commands issued after BeginQuery,
and the higher pipeline stages (e.g., vertex transformation) may have
started as well.
(9) What should the new 64 bit integer type be called?
RESOLVED: The new types will be called GLint64/GLuint64. The new
command suffixes will be i64 and ui64. These names clearly convey the
minimum size of the types. These types are similar to the C99 standard
type int_least64_t, but we use names similar to the C99 optional type
int64_t for simplicity.
Issues from ARB_timer_query
(10) What about tile-based implementations? The effects of a command are
not complete until the frame is completely rendered. Timing recorded
before the frame is complete may not be what developers expect. Also
the amount of time needed to render the same primitives is not
consistent, which conflicts with issue (8) above. The time depends on
how early or late in the scene it is placed.
RESOLVED: The current language supports tile-based rendering okay as it
is written. Developers are warned that using timers on tile-based
implementation may not produce results they expect since rendering is not
done in a linear order. Timing results are calculated when the frame is
completed and may depend on how early or late in the scene it is placed.
(11) Can the GL implementation use different clocks to implement the
TIME_ELAPSED and TIMESTAMP queries?
RESOLVED: Yes, the implementation can use different internal clocks to
implement TIME_ELAPSED and TIMESTAMP. If different clocks are
used it is possible there is a slight discrepancy when comparing queries
made from TIME_ELAPSED and TIMESTAMP; they may have slight
differences when both are used to measure the same sequence. However, this
is unlikely to affect real applications since comparing the two queries is
not expected to be useful.
Issues
(12) What should we call this extension?
RESOLVED: EXT_disjoint_timer_query
(13) Why is this done as a separate extension instead of just supporting
ARB_timer_query?
ARB_timer_query is written against OpenGL 3.2, which includes a lot of
the required support for dealing with query objects. None of these
functions or tokens exist in OpenGL ES, and as such have to be added in
this specification.
(14) How does this extension differ from ARB_timer_query?
This extension contains most ARB_timer_query behavior unchanged as well
as adds the ability to detect GPU issues using GPU_DISJOINT_EXT.
(15) Are query objects shareable between multiple contexts?
RESOLVED: No. Query objects are lightweight and we normally share
large data across contexts. Also, being able to share query objects
across contexts is not particularly useful. In order to do the async
query across contexts, a query on one context would have to be finished
before the other context could query it.
(16) How does this extension interact with EXT_occlusion_query_boolean?
This extension redefines the Query Api originally defined in the EXT-
_occlusion_query_boolean. If both EXT_disjoint_timer_query and EXT-
_occlusion_query_boolean are supported, the rules and specification
regarding any overlap will be governed by the EXT_occlusion_query_boolean
extension.
This extension should redefine the functionality in the same way, but if
some discrepancy is found and both are supported EXT_disjoint_timer_query
will yield to the rules and specifications governing the overlap in the
order above.
(17) How does this extension interact with the OpenGL ES 3.0 specification?
Some of the functionality and requirements described here overlap with the
OpenGL ES 3.0 specification. Any overlap for the functions or tokens in
this extension were meant to complement each other, but the OpenGL ES 3.0
spec takes precedence. If the implementation supports OpenGL ES 3.0 then
it should support both the core non-decorated functions and the EXT
decorated functions.
(18) How do times from BeginQueryEXT/EndQueryEXT with a <target> of
TIME_ELAPSED_EXT and QueryCounterEXT with a <target> of TIMESTAMP_EXT
compare on some Qualcomm and ARM tiling GPUs?
This does not describe all tiling GPUs, but it is how some tiling GPUs from
ARM, Qualcomm, and possibly other vendors work. This is just an
implementation note and there is no guarantee all ARM and Qualcomm
implementations will work this way.
TIME_ELAPSED_EXT will be a summation of all the time spent on the workload
between begin and end. Tiling architectures might split this work up over a
binning pass and rendering many different tiles. It is up to the hardware
and/or driver to add up all the time spent on the work between begin and end
and report a single number making the implementation transparent to
developers using this feature. If the binning pass happens in parallel to
rendering pass this time would not be counted twice. On some
implementations this does not include the time to copy tile memory to or from
the frame buffer in system memory, and on other implementations this time
is included.
TIMESTAMP_EXT is the time when all the commands are complete and copied out
of tile memory to the framebuffer in system memory. This can result in a
courser grain timestamp than developers familiar with immediate GPUs expect.
For example all the draws to an FBO can often all get the same timestamp, or
even all the draw calls to multiple FBOs can end up with the same timestamp.
If some operation causes a midframe store/load (such as flush or readPixels)
then that would create another point for timestamps, but is a lot of extra
work for the GPU so it should be avoided.
If a preemption event happens before the TIMESTAMP_EXT is reported then that
time will include the time for preemption. With TIME_ELAPSED_EXT it is
undefined if the preemption time is counted or not. Some hardware will
count the preemption time (even though it is from a different context). For
this behavior GPU_DISJOINT_EXT will be set so you know there was an event
from a different context affecting results. Other hardware will not count
the time spent in the preempting context and for this cases GPU_DISJOINT_EXT
will not be set.
Revision History
Revision 9, 2020/11/20 (xndcn)
- Minor fix of code sample
Revision 8, 2019/12/11 (Jon Leech)
- Add actual spec language defining GetInteger64vEXT (github
OpenGL-Registry issue 326)
Revision 7, 2016/9/2 (Maurice Ribble)
- Clarify language dealing with GetInteger64v
Revision 6, 2016/7/15 (Maurice Ribble)
- Clarified some outstanding questions about tiling GPUs
- Added issue 18
Revision 5, 2013/6/5
- Minor cleanup to match new gl2ext.h
Revision 4, 2013/4/25 (Jon Leech)
- Cleanup for publication
- Fix value assigned to GPU_DISJOINT_EXT
Revision 3, 2013/4/8
- Minor cleanup of code sample and re-wording
Revision 2, 2013/4/2
- Minor cleanup
Revision 1, 2013/1/2
- Copied from revision 1 of ANGLE_timer_query
- Added TIMESTAMP_EXT and GPU_DISJOINT_EXT