KB4505903 Fixes DPC Latency Issue
DPC is Windows shorthand for “deferred procedure call.” As explained at Resplendence.com (makers of the outstanding, free LatencyMon tool) the Windows thread dispatcher (aka “the scheduler”) handles prioritization of threads scheduled for execution on a given processor. Assume a high-priority thread works its way into the scheduling mix. Then, lower-priority calls for service get deferred and higher-priority threads run sooner. If that results in audio services delay, this can cause “stuttering” in sound output. And that, in fact, is what causes DPC Latency. (Literally, this term measures the amount of time it takes for a deferred procedure call to finally get a turn at the processor — and playback for audio.) That’s why learning that KB4505903 fixes DPC latency issue is good news, especially for those with affected PCs. Here’s a tweet from MS Engineer Pete Brown from Saturday, July 27:
Tweet Proclaims That KB4505903 Fixes DPC Latency Issue
As the preceding tweet capture shows, KB4505903 gets credit for fixing DPC latency spikes in Win10 1903. That’s good news for those with PCs suffering from audio latency issues. If this applies to PCs in your care, use LatencyMon to make before and after measurements. These should show visible (and audible) improvements in audio behavior. LatencyMon is a good tool for troubleshooting PC audio issues. It’s worth adding a copy to your admin toolbox for that reason. Who knows when another Windows 10 version or update may once again introduce audio delays, clicks, pops, or whathaveyou? I’ve dealt with such stuff personally since the Windows 8.x era, and repeatedly with various Win10 versions, too. Better safe than sorry!
For more information on symptoms of and resolution for this issue, see these various TenForums threads:
+ V1903 Causing DPC Latency Hits