Fix dropped kernel messages and stale state between driver loads#413
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wjhwjhn wants to merge 1 commit intoCobaltFusion:developfrom
Open
Fix dropped kernel messages and stale state between driver loads#413wjhwjhn wants to merge 1 commit intoCobaltFusion:developfrom
wjhwjhn wants to merge 1 commit intoCobaltFusion:developfrom
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…apture state on start/stop Raised the KernelReader poll rate from 1Hz to 1kHz, drained the driver ring per poll instead of reading one buffer and returning, and reset verbose/pass-through plus issued DBGV_CLEAR_DISPLAY around capture so state doesn't leak between driver loads.
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Hi! First of all, thanks for keeping DebugView++ alive — it's been a daily tool for me for a long time.
On my machine I was seeing kernel-mode messages arrive with visible latency, and the occasional message going missing when the driver produced a burst. I spent some time looking at what
KernelReaderdoes today and comparing it with Sysinternals DbgView to understand what was going on, and I wanted to share what I found in case it's useful.The driver doesn't expose an event handle and
DBGV_READ_LOGis a synchronous IOCTL, so both viewers end up polling. A couple of small things inKernelReader's current shape looked like they could probably be tightened up:PolledLogSource::pollFrequencyis in Hz, so the current value1means one poll per second, which seems to explain most of the latency I was seeing. Bumping it to1000(≈1 ms interval) helps a lot, and I addedtimeBeginPeriod(1)/timeEndPeriod(1)so the 1 ms sleep isn't rounded up to the default scheduler tick. That's whywinmmis linked in CMake now — happy to split that out if you'd prefer.Poll()issued a singleDBGV_READ_LOGper tick, so if the driver produced more than one buffer-worth between polls, the rest got dropped. I changed it to drain the ring until the driver reports 0 bytes, which mirrors what DbgView's read loop does (it tight-loops the IOCTL until empty, bounded by a 300 ms budget, before yielding).DBGV_CLEAR_DISPLAYis now sent beforeDBGV_CAPTURE_KERNELso stale events from a previous session aren't replayed into the new one. DbgView does the same on startup.DBGV_UNCAPTURE_KERNEL, andm_pBufis nulled afterfreeto avoid a dangling pointer if start/stop is repeated.I'm very open to changing any of this — I've only been in this code briefly, so if any of the above is wrong about the design intent, or there's a different direction you'd prefer, I'd be happy to revise. Thanks again for taking a look!