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| ohm_gl_fix:phase2_2026-04-30 [2026/04/30 18:15] – [6. Known failure modes — consolidated] markus_fritsche | ohm_gl_fix:phase2_2026-04-30 [2026/05/01 13:08] (current) – rewrap paragraphs (DokuWiki single-newline fix) markus_fritsche |
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| ====== Phase 2 — Situation Analysis (ohm_gl_fix iteration 1) ====== | ====== Phase 2 — Situation Analysis (ohm_gl_fix iteration 1) ====== |
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| Substrate enumeration on ''ohm'' (PineTab2, RK3566, Mali-G52 MP2, | Substrate enumeration on ''ohm'' (PineTab2, RK3566, Mali-G52 MP2, hantro-vpu, kernel ''6.19.10-danctnix1-1-pinetab2''), 2026-04-30. |
| hantro-vpu, kernel ''6.19.10-danctnix1-1-pinetab2''), 2026-04-30. | |
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| Phase 1 lock: [[ohm_gl_fix:phase1_2026-04-30|Phase 1 goal formulation, 2026-04-30]]. | Phase 1 lock: [[ohm_gl_fix:phase1_2026-04-30|Phase 1 goal formulation, 2026-04-30]]. Goal target: on ''bbb_1080p30_h264.mp4'' with ''mpv --hwdec=v4l2request --vo=gpu-next'' over a 60 s steady-state window, drops drop from baseline 1039/1440 (72 %) into the ''gst v4l2slh264dec → waylandsink'' transient-startup floor — equivalently, EGLImage-import ceases to be the binding constraint. |
| Goal target: on ''bbb_1080p30_h264.mp4'' with | |
| ''mpv --hwdec=v4l2request --vo=gpu-next'' over a 60 s steady-state window, | |
| drops drop from baseline 1039/1440 (72 %) into the | |
| ''gst v4l2slh264dec → waylandsink'' transient-startup floor — equivalently, | |
| EGLImage-import ceases to be the binding constraint. | |
| |
| This page is descriptive, not prescriptive. No plan here; the plan is | This page is descriptive, not prescriptive. No plan here; the plan is Phase 4. If something below turns out to be the wrong thing to measure once Phase 3 baselines run, that's a Phase 3→1 loopback, not a Phase 2 revision. |
| Phase 4. If something below turns out to be the wrong thing to measure | |
| once Phase 3 baselines run, that's a Phase 3→1 loopback, not a Phase 2 | |
| revision. | |
| |
| ---- | ---- |
| ===== 2. EGL/GLES extensions advertised ===== | ===== 2. EGL/GLES extensions advertised ===== |
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| EGL client extensions: | EGL client extensions: ''EGL_EXT_client_extensions, EGL_EXT_device_*, EGL_EXT_explicit_device, EGL_EXT_platform_base, EGL_EXT_platform_{wayland,x11,xcb,device}, EGL_KHR_debug, EGL_KHR_platform_{gbm,wayland,x11}, EGL_MESA_platform_{gbm,surfaceless}''. |
| ''EGL_EXT_client_extensions, EGL_EXT_device_*, EGL_EXT_explicit_device, | |
| EGL_EXT_platform_base, EGL_EXT_platform_{wayland,x11,xcb,device}, | |
| EGL_KHR_debug, EGL_KHR_platform_{gbm,wayland,x11}, | |
| EGL_MESA_platform_{gbm,surfaceless}''. | |
| |
| EGL display extensions (panfrost, both GBM and Wayland) — selecting the | EGL display extensions (panfrost, both GBM and Wayland) — selecting the ones load-bearing for this campaign: |
| ones load-bearing for this campaign: | |
| |
| * **''EGL_EXT_image_dma_buf_import''** ✓ — base import path. | * **''EGL_EXT_image_dma_buf_import''** ✓ — base import path. |
| * ''EGL_ANDROID_native_fence_sync'' ✓ — sync-fd interop with V4L2 out-fences. | * ''EGL_ANDROID_native_fence_sync'' ✓ — sync-fd interop with V4L2 out-fences. |
| * ''EGL_KHR_partial_update'' ✓. | * ''EGL_KHR_partial_update'' ✓. |
| * Context flags: ''EGL_KHR_no_config_context'', ''EGL_KHR_create_context'', | * Context flags: ''EGL_KHR_no_config_context'', ''EGL_KHR_create_context'', ''EGL_KHR_create_context_no_error'', ''EGL_IMG_context_priority''. |
| ''EGL_KHR_create_context_no_error'', ''EGL_IMG_context_priority''. | |
| |
| What ''eglinfo'' does **not** report, and what we therefore still need before Phase 4 (so this is a Phase 3 baseline action, not a Phase 2 hole): the per-format modifier list returned by ''eglQueryDmaBufModifiersEXT(DRM_FORMAT_NV12)'' and the ''external_only'' flag for each modifier. That's the data point that decides whether a kernel-allocated dmabuf can flow into a regular 2D sampler in libplacebo's GL path or only into ''samplerExternalOES''. | What ''eglinfo'' does **not** report, and what we therefore still need before Phase 4 (so this is a Phase 3 baseline action, not a Phase 2 hole): the per-format modifier list returned by ''eglQueryDmaBufModifiersEXT(DRM_FORMAT_NV12)'' and the ''external_only'' flag for each modifier. That's the data point that decides whether a kernel-allocated dmabuf can flow into a regular 2D sampler in libplacebo's GL path or only into ''samplerExternalOES''. |
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| GL ES extensions are advertised at GLES 3.1 level — full extension string lives in ''eglinfo'''s GBM block; nothing surprising for a Mali-G52 panfrost build. ''es2_info'' cannot run from an SSH session without a display; the Wayland ''eglinfo'' GLES profile already covers the same | GL ES extensions are advertised at GLES 3.1 level — full extension string lives in ''eglinfo'''s GBM block; nothing surprising for a Mali-G52 panfrost build. ''es2_info'' cannot run from an SSH session without a display; the Wayland ''eglinfo'' GLES profile already covers the same ground. |
| ground. | |
| |
| ===== 3. V4L2 buffer-pool size on the hantro path ===== | ===== 3. V4L2 buffer-pool size on the hantro path ===== |
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| Probe: ''strace -f -e ioctl ffmpeg -hwaccel v4l2request | Probe: ''strace -f -e ioctl ffmpeg -hwaccel v4l2request -hwaccel_output_format drm_prime -i bbb_1080p30_h264.mp4 -frames:v 60 -f null -'' against ''/dev/video1'' (hantro-vpu, mainline ''rockchip,rk3568-vpu-dec''). |
| -hwaccel_output_format drm_prime -i bbb_1080p30_h264.mp4 -frames:v 60 | |
| -f null -'' against ''/dev/video1'' (hantro-vpu, mainline | |
| ''rockchip,rk3568-vpu-dec''). | |
| |
| Result: | Result: |
| * ''kwin 1:6.6.4-1'', ''plasma-workspace 6.6.4-1'', ''plasma-desktop 6.6.4-1''. | * ''kwin 1:6.6.4-1'', ''plasma-workspace 6.6.4-1'', ''plasma-desktop 6.6.4-1''. |
| * ''kwin_wayland --version'' → ''kwin 6.6.4''. | * ''kwin_wayland --version'' → ''kwin 6.6.4''. |
| * Live process tree: ''kwin_wayland --wayland-fd 7 --socket wayland-0 | * Live process tree: ''kwin_wayland --wayland-fd 7 --socket wayland-0 --xwayland-fd 8 --xwayland-fd 9 --xwayland-display :0 ... --xwayland'', launched by ''startplasma-wayland'' under sddm session. |
| --xwayland-fd 8 --xwayland-fd 9 --xwayland-display :0 ... --xwayland'', | |
| launched by ''startplasma-wayland'' under sddm session. | |
| * The ''GL_POINT_SPRITE'', ''GL_ALPHA'' ''glTexSubImage2D'' cascade observed in the 2026-04-30 startup logs is **labelled background noise**: it's KWin's compatibility-profile feature probe at compositor init, fires once at session start, and is not on the per-frame video critical path. Phase 3 instrumentation must filter or clearly attribute these events so they don't pollute per-frame import attribution. | * The ''GL_POINT_SPRITE'', ''GL_ALPHA'' ''glTexSubImage2D'' cascade observed in the 2026-04-30 startup logs is **labelled background noise**: it's KWin's compatibility-profile feature probe at compositor init, fires once at session start, and is not on the per-frame video critical path. Phase 3 instrumentation must filter or clearly attribute these events so they don't pollute per-frame import attribution. |
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| ===== 6. Known failure modes — consolidated ===== | ===== 6. Known failure modes — consolidated ===== |
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| Inherited from the ohm_gl_fix README and the fourier Phase 5 page. | Inherited from the ohm_gl_fix README and the fourier Phase 5 page. Listed here so they don't get re-discovered later. |
| Listed here so they don't get re-discovered later. | |
| |
| * **R6 — Per-frame fresh EGLImage allocation (the campaign's primary lever).** mpv ''--vo=gpu-next'' re-imports each NV12 dmabuf fd into a fresh EGLImage on every decoded frame instead of caching by fd identity. Combined with the §3 result (9-fd capture ring, ~160× reuse over 60 s) this is where the cost is concentrated. | * **R6 — Per-frame fresh EGLImage allocation (the campaign's primary lever).** mpv ''--vo=gpu-next'' re-imports each NV12 dmabuf fd into a fresh EGLImage on every decoded frame instead of caching by fd identity. Combined with the §3 result (9-fd capture ring, ~160× reuse over 60 s) this is where the cost is concentrated. |
| ===== Success-transition lock-in ===== | ===== Success-transition lock-in ===== |
| |
| Numbers locking the journey from baseline to goal live in | Numbers locking the journey from baseline to goal live in ''metrics.csv'' (sibling file). Four rows: ''phase1_baseline'' (138 % CPU, 1039/1440 drops, 72 %), ''phase1_reference'' and ''phase1_reference_fs'' (the gst→waylandsink floor: 6–7 % CPU, 0/1488 drops), and ''phase1_goal_target'' (post-warmup drops = 0; warmup = first 10 s with ≤ 10 drops tolerated). Binding cell is ''phase1_goal_target.drops_post_warmup''; the ''drops'' cell carries the warmup sanity cap (10) so the path can't trivially satisfy "0 post-warmup" by stretching warmup. Phase 3 must decompose the baseline 1039 drops into warmup vs post-warmup before any Phase 4 prediction is made. Phase 3 and Phase 7 append rows; the ''role'' column distinguishes the metric from references. Loopback Phase 3 → Phase 1 (per dev-process) edits the goal_target row's binding cell rather than rewriting prose. |
| ''metrics.csv'' (sibling file). Four rows: ''phase1_baseline'' (138 % CPU, | |
| 1039/1440 drops, 72 %), ''phase1_reference'' and ''phase1_reference_fs'' | |
| (the gst→waylandsink floor: 6–7 % CPU, 0/1488 drops), and | |
| ''phase1_goal_target'' (post-warmup drops = 0; warmup = first 10 s with | |
| ≤ 10 drops tolerated). Binding cell is | |
| ''phase1_goal_target.drops_post_warmup''; the ''drops'' cell carries the | |
| warmup sanity cap (10) so the path can't trivially satisfy | |
| "0 post-warmup" by stretching warmup. Phase 3 must decompose the | |
| baseline 1039 drops into warmup vs post-warmup before any Phase 4 | |
| prediction is made. Phase 3 and Phase 7 append rows; the ''role'' column | |
| distinguishes the metric from references. Loopback Phase 3 → Phase 1 | |
| (per dev-process) edits the goal_target row's binding cell rather | |
| than rewriting prose. | |
| |
| ===== Locked metrics (success-transition) ===== | ===== Locked metrics (success-transition) ===== |
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| * Plan / approach. That's Phase 4. | * Plan / approach. That's Phase 4. |
| * Baseline numbers beyond Phase 1's 1039/1440 reference. Phase 3 does | * Baseline numbers beyond Phase 1's 1039/1440 reference. Phase 3 does the new measurements, including the modifier list and the fd-identity reuse count. |
| the new measurements, including the modifier list and the | * Patches, diffs, code reads of panfrost / libplacebo / mpv. Those enter at Phase 4 once we know which import call to replace. |
| fd-identity reuse count. | |
| * Patches, diffs, code reads of panfrost / libplacebo / mpv. Those | |
| enter at Phase 4 once we know which import call to replace. | |
| |
| ===== References used in this enumeration ===== | ===== References used in this enumeration ===== |
| |
| * ''~/src/ohm_gl_fix/README.md'' | * ''~/src/ohm_gl_fix/README.md'' |
| * ''~/src/fourier/README.md'' — baseline table at L173–234, gotchas at | * ''~/src/fourier/README.md'' — baseline table at L173–234, gotchas at L357–384. |
| L357–384. | |
| * ''~/.claude/projects/-home-mfritsche-src/memory/feedback_dev_process.md'' | * ''~/.claude/projects/-home-mfritsche-src/memory/feedback_dev_process.md'' |
| * DokuWiki: [[ohm_gl_fix:phase1_2026-04-30]], [[ohm_gl_fix:start]], | * DokuWiki: [[ohm_gl_fix:phase1_2026-04-30]], [[ohm_gl_fix:start]], [[fourier:phase5_2026-04-30]] (latter currently access-controlled in the wiki — local mirror in ''~/src/fourier/README.md''). |
| [[fourier:phase5_2026-04-30]] (latter currently access-controlled in the | |
| wiki — local mirror in ''~/src/fourier/README.md''). | |
| |
