feat: event-driven compositor_wait syscall — BWM CPU 34% → 20%#254
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feat: event-driven compositor_wait syscall — BWM CPU 34% → 20%#254
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New compositor_wait syscall (op=23) replaces BWM's polling loop with kernel-level blocking. BWM now sleeps in the kernel until woken by: - mark_window_dirty (client rendered new pixels) - Mouse movement (USB HID handler wakes compositor) - Window registry change (new/removed window) - 16ms timeout (keyboard input via stdin poll) Changes: - kernel: op=23 compositor_wait with COMPOSITOR_DIRTY_WAKE flag - kernel: REGISTRY_GENERATION atomic bumped on window register - kernel: USB HID mouse handler calls wake_compositor_if_waiting() - kernel: Removed duplicate blocking from op=16 composite_windows (compositor_wait now handles all blocking) - libbreenix: compositor_wait() wrapper returning (ready, registry_gen) - bwm: Event-driven main loop — only blits when DIRTY flag set, only discovers windows when REGISTRY flag set Results on Parallels ARM64 (1920x1200, 4 windows): - BWM CPU: 34% → ~20% (41% reduction) - Bounce FPS: ~130 → ~186 (43% increase) - Zero idle wakes (was 50% idle polling before) Combined with MAP_SHARED+occluded blit from previous PR: - BWM CPU: 70% → ~20% (71% total reduction) - Bounce FPS: ~100 → ~186 (86% total increase) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
compositor_waitsyscall (op=23): Blocks BWM in the kernel until work arrives — dirty window, mouse movement, registry change, or timeoutResults (Parallels ARM64, 1920x1200, 4 windows)
Combined total improvement from baseline:
Test plan
🤖 Generated with Claude Code