The captured traces contain per-frame patterns the bench did not exercise, and
first measurements show two of them are now the worst remaining multipliers -
which is exactly what the missing cases were hiding.
mc_pass_switch: the 26.2 snapshot switches render targets 132 times a frame and
re-declares draw buffers 198 times. Render-target churn is where a Vulkan
backend pays for render-pass breaks and where a tiler pays most on device, and
no case measured it. mc_state_toggle: Blaze3D brackets batches with blend
toggles - 46 enable/disable pairs and 28 blend-func changes per vanilla frame.
mc_tex_param: 26.2 re-sets texture parameters 612 times a frame, almost always
to the value already in place, so this measures redundant-parameter filtering.
mc_use_program: Sodium switches programs 62 times a frame with a mat4 upload on
each, roughly one switch per multi-draw.
All four live in the shared case file at the measured per-frame rates, so the
desktop harness, the on-device harness and the POST screen's Run Bench report
comparable numbers. First desktop measurements (ns/op, native / Espryt / Magma):
pass_switch 8877 / 18502 / 13896, state_toggle 1182 / 8526 / 8305,
tex_param 42 / 102 / 197, use_program 2182 / 10648 / 5096. The state-toggle
multiplier - 7x on both backends - is the largest newly exposed gap and the next
optimization target.
Unit tests 421/421; the Android JNI translation unit compiles against the
extended case set.
The Minecraft-shaped driver benchmark could only be run from a desktop shell
against a desktop driver, which is the wrong machine: MobileGL exists to run on
mobile GPUs, and nothing said what its translation costs there. This puts the
same cases on an Android device, both in the plugin's POST screen and from a
shell, and adds the native-driver baseline they have to be read against.
The cases move into DriverBenchCases.inc so both harnesses run byte-identical
bodies - the desktop program resolving entry points from one EGL provider, and
DriverBenchJni.cpp calling MobileGL's frontend in-process. The JNI file binds
every gl*/egl* name to MG_Impl by macro rather than by linkage: this library
legitimately has the platform libEGL and libGLESv3 in its own lookup scope, and
a benchmark that quietly measured the device driver instead of the translation
layer would have looked like very good news.
Frames are now closed with a fence wait instead of glFinish. MobileGL implements
glFinish and glFlush as no-ops, so the old loop timed submit-plus-GPU on a native
driver and submit-only on a MobileGL backend, and the two numbers did not
describe the same work.
To measure a device's own driver the cases needed to be expressible in GLES:
ESSL 3.20 twins of the four shaders (chosen at runtime from GL_VERSION, since
MobileGL is deliberately still fed desktop GLSL - translating it is the thing
under test), a multi-draw hook that loops DrawElementsBaseVertex where the
multi-draw entry point does not exist, and an EGL bootstrap that falls back from
desktop GL to GLES 3. The binary cross-compiles for arm64 unchanged.
BenchService hosts each run in its own process and exits afterwards. That is not
caution: the backend is latched from MOBILEGL_BACKEND_TYPE at initialization, so
Espryt and Magma can never share a process, and Espryt's teardown terminates the
process-default EGL display, which would take the POST activity's own EGL
objects with it.
Running it found that Magma could not create a windowless context on Mali at
all - CreateInstance required VK_EXT_headless_surface, which no mobile driver
here exposes, and aborted the process. The Xlib path already probes and falls
back to a hidden window for the same reason on NVIDIA; Android now probes too
and hands the WSI an AImageReader's ANativeWindow, a real producer surface
attached to no display whose images are never acquired. DriverPost reports the
extension's absence as a WARN so the fallback is visible rather than silent.
Measured on a Mali-G77 MC9 (native / Espryt / Magma, ns per operation):
5495 chunk draws 14397 / 36934 / 33763, the 26.2 per-draw uniform-range pattern
13710 / 31205 / 21252, sodium-style multi-draw 256956 / 238389 / 209527. The
translation costs about 2.4x per draw here against 5-9x on the desktop, because
the mobile driver's own per-call cost dwarfs it - and both backends beat the
native driver on multi-draw, which it has to emulate.
Desktop unit tests 421/421; the POST screen and both Run Bench buttons verified
on the device.
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