Add EGL_NV_context_priority_realtime extension
diff --git a/api/egl.xml b/api/egl.xml
index 6ec7433..97f390d 100644
--- a/api/egl.xml
+++ b/api/egl.xml
@@ -791,7 +791,9 @@
<enum value="0x3350" name="EGL_GL_COLORSPACE_SCRGB_LINEAR_EXT"/>
<enum value="0x3351" name="EGL_GL_COLORSPACE_SCRGB_EXT"/>
<enum value="0x3352" name="EGL_TRACK_REFERENCES_KHR"/>
- <unused start="0x3353" end="0x335F"/>
+ <unused start="0x3353" end="0x3356"/>
+ <enum value="0x3357" name="EGL_CONTEXT_PRIORITY_REALTIME_NV"/>
+ <unused start="0x3358" end="0x335F"/>
<enum value="0x3360" name="EGL_CTA861_3_MAX_CONTENT_LIGHT_LEVEL_EXT"/>
<enum value="0x3361" name="EGL_CTA861_3_MAX_FRAME_AVERAGE_LEVEL_EXT"/>
<enum value="0x3362" name="EGL_GL_COLORSPACE_DISPLAY_P3_LINEAR_EXT"/>
@@ -2821,6 +2823,11 @@
<enum name="EGL_COVERAGE_SAMPLES_NV"/>
</require>
</extension>
+ <extension name="EGL_NV_context_priority_realtime" supported="egl">
+ <require>
+ <enum name="EGL_CONTEXT_PRIORITY_REALTIME_NV"/>
+ </require>
+ </extension>
<extension name="EGL_NV_coverage_sample_resolve" supported="egl">
<require>
<enum name="EGL_COVERAGE_SAMPLE_RESOLVE_NV"/>
diff --git a/extensions/NV/EGL_NV_context_priority_realtime.txt b/extensions/NV/EGL_NV_context_priority_realtime.txt
new file mode 100644
index 0000000..5435c8c
--- /dev/null
+++ b/extensions/NV/EGL_NV_context_priority_realtime.txt
@@ -0,0 +1,195 @@
+Name
+
+ NV_context_priority_realtime
+
+Name Strings
+
+ EGL_NV_context_priority_realtime
+
+Contributors
+
+ Sandeep Shinde
+ Kirill Artamonov
+ Sami Kiminki
+ Donghan Ryu
+ Daniel Koch
+ Mark Kilgard
+
+Contacts
+
+ Sandeep Shinde, NVIDIA (sashinde 'at' nvidia 'dot' com)
+
+Status
+
+ Complete
+
+Version
+
+ Version 4 - November 21, 2017
+
+Number
+
+ EGL Extension #124
+
+Dependencies
+
+ Requires EGL 1.0.
+
+ Requires EGL_IMG_context_priority
+
+ This extension is written against the wording of the EGL 1.5
+ Specification - August 27, 2014 (but may be implemented against earlier
+ versions).
+
+Overview
+
+ This extension allows an EGLContext to be created with one extra
+ priority level in addition to three priority levels that are part of
+ EGL_IMG_context_priority extension.
+
+ This new level has extra privileges that are not available to other three
+ levels. Some of the privileges may include:
+ - Allow realtime priority to only few contexts
+ - Allow realtime priority only to trusted applications
+ - Make sure realtime priority contexts are executed immediately
+ - Preempt any current context running on GPU on submission of
+ commands for realtime context
+
+ The mechanism for determining which EGL context is allowed to use this
+ priority level is platform dependent.
+
+New Types
+
+ None
+
+New Procedures and Functions
+
+ None
+
+New Tokens
+
+ New attribute value accepted for the EGL_CONTEXT_PRIORITY_LEVEL_IMG
+ attribute in the <attrib_list> argument of eglCreateContext:
+
+ EGL_CONTEXT_PRIORITY_REALTIME_NV 0x3357
+
+Additions to Chapter 3 of the EGL 1.5 Specification (EGL Functions and Errors)
+
+ Add a NEW section "3.7.1.7 Context Priority" to specify the context
+ priority attribute for EGL_IMG_context_priority and values:
+
+ "3.7.1.7 Context Priority
+
+ The attribute EGL_CONTEXT_PRIORITY_LEVEL_IMG specifies a context
+ priority hint for a context supporting context priority. This
+ attribute's value may be one of EGL_CONTEXT_PRIORITY_HIGH_IMG,
+ EGL_CONTEXT_PRIORITY_MEDIUM_IMG, EGL_CONTEXT_PRIORITY_LOW_IMG,
+ or EGL_CONTEXT_PRIORITY_REALTIME_NV. The default value for
+ EGL_CONTEXT_PRIORITY_LEVEL_IMG is EGL_CONTEXT_PRIORITY_MEDIUM_IMG.
+
+ This attribute is a hint, as an implementation may not support
+ multiple contexts at some priority levels and system policy may limit
+ access to high priority contexts to appropriate system privilege
+ level.
+
+ The value EGL_CONTEXT_PRIORITY_REALTIME_NV requests the created
+ context run at the highest possible priority and be capable of
+ preempting the current executing context when commands are flushed
+ by such a realtime context.
+
+ This attribute is supported only for OpenGL and OpenGL ES contexts."
+
+ Within section 3.7.4 "Context Queries" amend the eglQueryContext
+ discussion as follows:
+
+ Change the sentence describing the attribute parameter to include
+ EGL_CONTEXT_PRIORITY_LEVEL_IMG so it reads:
+
+ "attribute must be set to EGL_CONFIG_ID, EGL_CONTEXT_CLIENT_TYPE,
+ EGL_CONTEXT_CLIENT_VERSION, EGL_RENDER_BUFFER, or
+ EGL_CONTEXT_PRIORITY_LEVEL_IMG."
+
+ After the discussion of "Querying EGL_RENDER_BUFFER", add:
+
+ "Querying EGL_CONTEXT_PRIORITY_LEVEL_IMG returns the priority this
+ context was actually created with. Note: this may not be the same
+ as specified at context creation time, due to implementation limits
+ on the number of contexts that can be created at a specific priority
+ level in the system."
+
+Issues
+
+ 1) The EGL_IMG_context_priority extension is written to amend the EGL
+ 1.4 specification. Should this extension amend EGL 1.5 or 1.4?
+
+ RESOLVED: EGL 1.5 because it is newer and better organized to
+ extend context attributes.
+
+ EGL 1.5 rewrites 3.7.1 "Creating Rendering Contexts" to have subsections
+ for different context attributes. This extension adds a new such section
+ that includes the EGL_IMG_context_priority attribute and values too.
+
+ 2) Is context priority hint supported for both OpenGL and OpenGL ES contexts?
+
+ RESOLVED: Yes.
+
+ 3) What is the intended application of the realtime priority level?
+
+ RESOLVED: One anticipated application is the system compositor
+ for a Head Mounted Display (HMD) requires realtime recomposition
+ for time-warping.
+
+ 4) What action causes a context with realtime priority to preempt
+ other contexts?
+
+ RESOLVED: Preemption by a context with realtime priority should
+ occur when there are pending rendering commands and an implicit or
+ explicit flush (i.e. glFlush or glFinish) occurs.
+
+ 5) What does "trusted" or "appropriate system privilege level"
+ mean in practice for a Linux-based operating system such as Android?
+
+ RESOLVED: Trusted means an application that has higher privileges
+ than other apps such as having CAP_SYS_NICE capability. On Android
+ such applications have to be registered in advance with the OS;
+ unpriviledged third party app cannot acquire this capability.
+
+ This restriction exists so arbitrary applications do not starve or
+ otherwise compromise the interactivity of the system overall.
+
+ 6) In practice how many realtime priority contexts can exist in a system to
+ get best performance?
+
+ RESOLVED: Only one realtime priority context should be active at a given
+ moment to get best performance.
+
+ 7) Can a context created with a realtime priority hint that is
+ in fact given a realtime priority, subsequently find that realtime
+ priority revoked and, if revoked, can it be restored?
+
+ RESOLVED: No, once a context is created with specific priority level, the
+ priority will not change for lifetime of the context. This means there will
+ not be revoking or restoring of realtime priority to already created context.
+
+ 8) The attrib_list for eglCreateContext could list the attribute
+ EGL_CONTEXT_PRIORITY_LEVEL_IMG multiple times with different valid values.
+ What happens in this case?
+
+ RESOLVED: Behavior is undefined in this case.
+
+ NVIDIA's EGL implementation handles such case by using the last (valid) attribute
+ value listed in the attrib_list array as the effective attribute value for
+ creating the context.
+
+ The EGL specification is unfortunately silent on this issue.
+
+
+Revision History
+ Version 1, 2016/11/23 (Sandeep Shinde)
+ - Initial version
+ Version 2, 2017/10/13 (Mark Kilgard)
+ - Complete and convert to NV extension
+ Version 3, 2017/10/31 (Sandeep Shinde)
+ - Few minor corrections. Issue 6 resolved.
+ Version 4, 2017/11/21 (Sandeep Shinde)
+ - Update enum value and add extension number
diff --git a/index.php b/index.php
index 442d86d..03da013 100644
--- a/index.php
+++ b/index.php
@@ -313,6 +313,8 @@
</li>
<li value=123> <a href="extensions/ANDROID/EGL_ANDROID_get_native_client_buffer.txt">EGL_ANDROID_get_native_client_buffer</a>
</li>
+<li value=124> <a href="extensions/NV/EGL_NV_context_priority_realtime.txt">EGL_NV_context_priority_realtime</a>
+</li>
</ol>
<h6> Providing Feedback on the Registry </h6>
diff --git a/registry.tcl b/registry.tcl
index f4367af..aa9fd63 100644
--- a/registry.tcl
+++ b/registry.tcl
@@ -644,4 +644,9 @@
flags public
filename extensions/ANDROID/EGL_ANDROID_get_native_client_buffer.txt
}
-# Next free extension number: 124
+extension EGL_NV_context_priority_realtime {
+ number 124
+ flags public
+ filename extensions/NV/EGL_NV_context_priority_realtime.txt
+}
+# Next free extension number: 125
