diff -r 000000000000 -r 6474c204b198 gfx/angle/extensions/ANGLE_timer_query.txt --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gfx/angle/extensions/ANGLE_timer_query.txt Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,591 @@ +Name + + ANGLE_timer_query + +Name Strings + + GL_ANGLE_timer_query + +Contributors + + Contributors to ARB_occlusion_query + Contributors to EXT_timer_query + Contributors to ARB_timer_query + Ben Vanik, Google Inc. + Daniel Koch, TransGaming Inc. + +Contact + + Ben Vanik, Google Inc. (benvanik 'at' google 'dot' com) + +Status + + Draft + +Version + + Last Modified Date: Apr 28, 2011 + Author Revision: 1 + +Number + + OpenGL ES Extension #?? + +Dependencies + + OpenGL ES 2.0 is required. + + The extension is written against the OpenGL ES 2.0 specification. + +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. + +IP Status + + No known IP claims. + +New Procedures and Functions + + void GenQueriesANGLE(sizei n, uint *ids); + void DeleteQueriesANGLE(sizei n, const uint *ids); + boolean IsQueryANGLE(uint id); + void BeginQueryANGLE(enum target, uint id); + void EndQueryANGLE(enum target); + void QueryCounterANGLE(uint id, enum target); + void GetQueryivANGLE(enum target, enum pname, int *params); + void GetQueryObjectivANGLE(uint id, enum pname, int *params); + void GetQueryObjectuivANGLE(uint id, enum pname, uint *params); + void GetQueryObjecti64vANGLE(uint id, enum pname, int64 *params); + void GetQueryObjectui64vANGLE(uint id, enum pname, uint64 *params); + +New Tokens + + Accepted by the parameter of GetQueryivANGLE: + + QUERY_COUNTER_BITS_ANGLE 0x8864 + CURRENT_QUERY_ANGLE 0x8865 + + Accepted by the parameter of GetQueryObjectivANGLE, + GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, and + GetQueryObjectui64vANGLE: + + QUERY_RESULT_ANGLE 0x8866 + QUERY_RESULT_AVAILABLE_ANGLE 0x8867 + + Accepted by the parameter of BeginQueryANGLE, EndQueryANGLE, and + GetQueryivANGLE: + + TIME_ELAPSED_ANGLE 0x88BF + + Accepted by the parameter of GetQueryivANGLE and + QueryCounterANGLE: + + TIMESTAMP_ANGLE 0x8E28 + +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 int64ANGLE + ui64 uint64ANGLE + + (Modify table 2.2, GL data types) Add two new types: + + GL Type Minimum Bit Width Description + ------- ----------------- ----------------------------- + int64ANGLE 64 Signed 2's complement integer + uint64ANGLE 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 GenQueriesANGLE(sizei n, uint *ids); + + returns previously unused query object names in . These + names are marked as used, but no object is associated with them until + the first time they are used by BeginQueryANGLE. 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 DeleteQueriesANGLE(sizei n, const uint *ids); + + contains names of query objects to be deleted. After a + query object is deleted, its name is again unused. Unused names in + 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 BeginQueryANGLE(enum target, uint id); + void EndQueryANGLE(enum target); + + where is TIME_ELAPSED_ANGLE. If BeginQueryANGLE is called + with an unused , that name is marked as used and associated with + a new query object. + + If BeginQueryANGLE is called with an of zero, if the active query + object name for is non-zero, if is the name of an existing + query object whose type does not match , or if is the active + query object name for any query type, the error INVALID_OPERATION is + generated. If EndQueryANGLE is called while no query with the same target + is in progress, an INVALID_OPERATION error is generated. + + When BeginQueryANGLE and EndQueryANGLE are called with a of + TIME_ELAPSED_ANGLE, 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. The BeginQueryANGLE and EndQueryANGLE 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, , 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 an 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 QueryCounterANGLE(uint id, enum target); + + is called with TIMESTAMP_ANGLE, 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. When the time is recorded, the query result for + that object is marked available. QueryCounterANGLE timer queries can be + used within a BeginQueryANGLE / EndQueryANGLE block where the is + TIME_ELAPSED_ANGLE and it does not affect the result of that query object. + The error INVALID_OPERATION is generated if the is already in use + within a BeginQueryANGLE/EndQueryANGLE block." + +Additions to Chapter 6 of the OpenGL ES 2.0 Specification (State and State +Requests) + + Add a new section 6.1.9 "Timer Queries": + + "The command + + boolean IsQueryANGLE(uint id); + + returns TRUE if is the name of a query object. If is zero, + or if is a non-zero value that is not the name of a query + object, IsQueryANGLE returns FALSE. + + Information about a query target can be queried with the command + + void GetQueryivANGLE(enum target, enum pname, int *params); + + identifies the query target and can be TIME_ELAPSED_ANGLE or + TIMESTAMP_ANGLE for timer queries. + + If is CURRENT_QUERY_ANGLE, the name of the currently active query + for , or zero if no query is active, will be placed in . + + If is QUERY_COUNTER_BITS_ANGLE, the implementation-dependent number + of bits used to hold the query result for will be placed in + . The number of query counter bits may be zero, in which case + the counter contains no useful information. + + For timer queries (TIME_ELAPSED_ANGLE and TIMESTAMP_ANGLE), 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 GetQueryObjectivANGLE(uint id, enum pname, int *params); + void GetQueryObjectuivANGLE(uint id, enum pname, uint *params); + void GetQueryObjecti64vANGLE(uint id, enum pname, int64 *params); + void GetQueryObjectui64vANGLE(uint id, enum pname, uint64 *params); + + If is not the name of a query object, or if the query object + named by is currently active, then an INVALID_OPERATION error is + generated. + + If is QUERY_RESULT_ANGLE, then the query object's result + value is returned as a single integer in . 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 + is QUERY_RESULT_AVAILABLE_ANGLE, 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]vANGLE, 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 and ." + +Errors + + The error INVALID_VALUE is generated if GenQueriesANGLE is called where + is negative. + + The error INVALID_VALUE is generated if DeleteQueriesANGLE is called + where is negative. + + The error INVALID_OPERATION is generated if BeginQueryANGLE is called + when a query of the given is already active. + + The error INVALID_OPERATION is generated if EndQueryANGLE is called + when a query of the given is not active. + + The error INVALID_OPERATION is generated if BeginQueryANGLE is called + where is zero. + + The error INVALID_OPERATION is generated if BeginQueryANGLE is called + where is the name of a query currently in progress. + + The error INVALID_OPERATION is generated if BeginQueryANGLE is called + where is the name of an existing query object whose type does not + match . + + The error INVALID_ENUM is generated if BeginQueryANGLE or EndQueryANGLE + is called where is not TIME_ELAPSED_ANGLE. + + The error INVALID_ENUM is generated if GetQueryivANGLE is called where + is not TIME_ELAPSED_ANGLE or TIMESTAMP_ANGLE. + + The error INVALID_ENUM is generated if GetQueryivANGLE is called where + is not QUERY_COUNTER_BITS_ANGLE or CURRENT_QUERY_ANGLE. + + The error INVALID_ENUM is generated if QueryCounterANGLE is called where + is not TIMESTAMP_ANGLE. + + The error INVALID_OPERATION is generated if QueryCounterANGLE is called + on a query object that is already in use inside a + BeginQueryANGLE/EndQueryANGLE. + + The error INVALID_OPERATION is generated if GetQueryObjectivANGLE, + GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, or + GetQueryObjectui64vANGLE is called where is not the name of a query + object. + + The error INVALID_OPERATION is generated if GetQueryObjectivANGLE, + GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, or + GetQueryObjectui64vANGLE is called where is the name of a currently + active query object. + + The error INVALID_ENUM is generated if GetQueryObjectivANGLE, + GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, or + GetQueryObjectui64vANGLE is called where is not + QUERY_RESULT_ANGLE or QUERY_RESULT_AVAILABLE_ANGLE. + +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_ANGLE Z+ GetQueryivANGLE 0 active query ID 5.3 + QUERY_RESULT_ANGLE Z+ GetQueryObjectuivANGLE, 0 samples-passed count 5.3 + GetQueryObjectui64vANGLE + QUERY_RESULT_AVAILABLE_ANGLE B GetQueryObjectivANGLE 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_ANGLE Z+ GetQueryivANGLE see 6.1.9 Number of bits in 6.1.9 + query counter + +Examples + + (1) Here is some rough sample code that demonstrates the intended usage + of this extension. + + GLint queries[N]; + GLint available = 0; + // timer queries can contain more than 32 bits of data, so always + // query them using the 64 bit types to avoid overflow + GLuint64ANGLE timeElapsed = 0; + + // Create a query object. + glGenQueriesANGLE(N, queries); + + // Start query 1 + glBeginQueryANGLE(GL_TIME_ELAPSED_ANGLE, queries[0]); + + // Draw object 1 + .... + + // End query 1 + glEndQueryANGLE(GL_TIME_ELAPSED_ANGLE); + + ... + + // Start query N + glBeginQueryANGLE(GL_TIME_ELAPSED_ANGLE, queries[N-1]); + + // Draw object N + .... + + // End query N + glEndQueryANGLE(GL_TIME_ELAPSED_ANGLE); + + // Wait for all results to become available + while (!available) { + glGetQueryObjectivANGLE(queries[N-1], GL_QUERY_RESULT_AVAILABLE_ANGLE, &available); + } + + for (i = 0; i < N; i++) { + // See how much time the rendering of object i took in nanoseconds. + glGetQueryObjectui64vANGLE(queries[i], GL_QUERY_RESULT_ANGLE, &timeElapsed); + + // Do something useful with the time. 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 is basically the same as the example above but uses + QueryCounter instead. + + GLint queries[N+1]; + GLint available = 0; + // timer queries can contain more than 32 bits of data, so always + // query them using the 64 bit types to avoid overflow + GLuint64ANGLE timeStart, timeEnd, timeElapsed = 0; + + // Create a query object. + glGenQueriesANGLE(N+1, queries); + + // Query current timestamp 1 + glQueryCounterANGLE(queries[0], GL_TIMESTAMP_ANGLE); + + // Draw object 1 + .... + + // Query current timestamp N + glQueryCounterANGLE(queries[N-1], GL_TIMESTAMP_ANGLE); + + // Draw object N + .... + + // Query current timestamp N+1 + glQueryCounterANGLE(queries[N], GL_TIMESTAMP_ANGLE); + + // Wait for all results to become available + while (!available) { + glGetQueryObjectivANGLE(queries[N], GL_QUERY_RESULT_AVAILABLE_ANGLE, &available); + } + + for (i = 0; i < N; i++) { + // See how much time the rendering of object i took in nanoseconds. + glGetQueryObjectui64vANGLE(queries[i], GL_QUERY_RESULT_ANGLE, &timeStart); + glGetQueryObjectui64vANGLE(queries[i+1], GL_QUERY_RESULT_ANGLE, &timeEnd); + timeElapsed = timeEnd - timeStart; + + // Do something useful with the time. Note that care should be + // taken to use all significant bits of the result, not just the + // least significant 32 bits. + AdjustObjectLODBasedOnDrawTime(i, timeElapsed); + } + +Issues from EXT_timer_query + + (1) What time interval is being measured? + + RESOLVED: The timer starts when all commands prior to BeginQuery() 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 EndQuery() 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, int64ANGLE and uint64ANGLE, 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 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 GLint64ANGLE/GLuint64ANGLE. 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 implemenation 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: ANGLE_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 a subset of the query support required to use it from the core + OpenGL 3.2 spec. It omits the glGetInteger(TIMESTAMP) functionality used to + query the current time on the GPU, but the behavior for all remaining + functionality taken from ARB_timer_query is the same. + + (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. + +Revision History + + Revision 1, 2011/04/28 + - copied from revision 9 of ARB_timer_query and revision 7 of + ARB_occlusion_query + - removed language that was clearly not relevant to ES2 + - rebased changes against the OpenGL ES 2.0 specification