The Tor Browser: gfx/angle/extensions/ANGLE_timer_query.txt@6474c204b198 (annotated)

gfx/angle/extensions/ANGLE_timer_query.txt@6474c204b198 (annotated)

gfx/angle/extensions/ANGLE_timer_query.txt

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 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 <pname> parameter of GetQueryivANGLE:
         QUERY_COUNTER_BITS_ANGLE                       0x8864
         CURRENT_QUERY_ANGLE                            0x8865
     Accepted by the <pname> parameter of GetQueryObjectivANGLE,
     GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, and
     GetQueryObjectui64vANGLE:
         QUERY_RESULT_ANGLE                             0x8866
         QUERY_RESULT_AVAILABLE_ANGLE                   0x8867
     Accepted by the <target> parameter of BeginQueryANGLE, EndQueryANGLE, and
     GetQueryivANGLE:
         TIME_ELAPSED_ANGLE                             0x88BF
     Accepted by the <target> 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 <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 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);
     <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 BeginQueryANGLE(enum target, uint id);
       void EndQueryANGLE(enum target);
     where <target> is TIME_ELAPSED_ANGLE.  If BeginQueryANGLE is called
     with an unused <id>, that name is marked as used and associated with
     a new query object.
     If BeginQueryANGLE 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 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 <target> 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, <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
 ^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 <target> 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 <target> is
     TIME_ELAPSED_ANGLE 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 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 <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, IsQueryANGLE returns FALSE.
     Information about a query target can be queried with the command
       void GetQueryivANGLE(enum target, enum pname, int *params);
     <target> identifies the query target and can be TIME_ELAPSED_ANGLE or
     TIMESTAMP_ANGLE for timer queries.
     If <pname> is CURRENT_QUERY_ANGLE, 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_ANGLE, 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_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 <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_ANGLE, 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_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 <target> and <id>."
 Errors
     The error INVALID_VALUE is generated if GenQueriesANGLE is called where
     <n> is negative.
     The error INVALID_VALUE is generated if DeleteQueriesANGLE is called
     where <n> is negative.
     The error INVALID_OPERATION is generated if BeginQueryANGLE is called
     when a query of the given <target> is already active.
     The error INVALID_OPERATION is generated if EndQueryANGLE is called
     when a query of the given <target> is not active.
     The error INVALID_OPERATION is generated if BeginQueryANGLE is called
     where <id> is zero.
     The error INVALID_OPERATION is generated if BeginQueryANGLE is called
     where <id> is the name of a query currently in progress.
     The error INVALID_OPERATION is generated if BeginQueryANGLE 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 BeginQueryANGLE or EndQueryANGLE
     is called where <target> is not TIME_ELAPSED_ANGLE.
     The error INVALID_ENUM is generated if GetQueryivANGLE is called where
     <target> is not TIME_ELAPSED_ANGLE or TIMESTAMP_ANGLE.
     The error INVALID_ENUM is generated if GetQueryivANGLE is called where
     <pname> is not QUERY_COUNTER_BITS_ANGLE or CURRENT_QUERY_ANGLE.
     The error INVALID_ENUM is generated if QueryCounterANGLE is called where
     <target> 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 <id> is not the name of a query
     object.
     The error INVALID_OPERATION is generated if GetQueryObjectivANGLE,
     GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, or
     GetQueryObjectui64vANGLE is called where <id> is the name of a currently
     active query object.
     The error INVALID_ENUM is generated if GetQueryObjectivANGLE,
     GetQueryObjectuivANGLE, GetQueryObjecti64vANGLE, or
     GetQueryObjectui64vANGLE is called where <pname> 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
 -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 <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 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

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gfx/angle/extensions/ANGLE_timer_query.txt