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DeeJanuzandClaude Opus 5.5
060b4957f8
While copying, ft-eyegrab woke every 300 us (about 1,500 to 3,000 times a second) and fingerprinted all eight slots each time: 8 x 256 strided reads from DMA-BUF memory. - Each look now checks only the slot each camera writes next. The order is known (camera 0 3,0,1,2; camera 1 7,5,4,6,5,7,6,4), and the next slot follows from the last two; the table starts from those orders and learns from every frame, so a SteamVR update that changes them costs a few seconds of full scans, not frames. - A camera with nothing in its expected slot 1.5 frames after its last one, or with no order yet, gets all four slots checked, as before. A frame that turns up in an unexpected slot means full scans for that camera for 2 s. - A slot's fingerprint is taken again when it stops being one of the two in use, so a later check sees only a new frame. A frame is still passed on when its camera starts the frame after next. - Between frames it sleeps until 2.5 ms before the next is due, then looks every 1 ms, with 0.5 ms of timer slack (PR_SET_TIMERSLACK, --share only). With no frames from either camera for 0.5 s (headset off) it looks every 4 ms. - --rec keeps its 0.3 ms polls (and the expected-slot checks), for its timestamps. Tested offline by building poll_frames against simulated cameras that write each frame in four bursts, the last after the next frame starts (6 s, both cameras): 1,076 frames passed on, none torn or skipped, with the known orders and with camera 1 in a different order. Wakeups 1,486/s -> 207/s, the poller's CPU 3.6% -> 0.8% of a core (in plain memory; the real DMA-BUF reads cost more), and a frame's start is seen 1.35 ms after it begins on average instead of 0.76. With a camera stalling 15 ms every 2 s, the old poller passed on 22 torn frames and the new one 8 or fewer. Built (glibc 2.38 symbols at most, the host has 2.39), not installed: it runs as root from /etc/frametop, so it takes effect only after gaze/tracker/install.sh (sudo). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>