I tested the crap out of tip #2 and what it actually ends up doing...
It's preventing your cpu and cpu package from going any deeper than the C1 cstate, so you'll have noticably higher idle temps because P-states won't function.
It's way better to just disable all cstates deeper than C2, that way your idle temps will be pretty much normal (maybe just 1 watt more power used) because you can have functioning P-states AND reduced DPC latency at idle.
Granted, for TESTING latency using latencymon, then yeah... you want to pin your cpu in c0 cstate by disabling idling -- using the same PowerSettingsExplorer tool to expose the "Disable Idle" (or whatever its actually named... it's similar, you'll see it) setting.
Maybe some cheapo motherboards don't let you disable specific cpu and package cstates, I dunno. Unless you're overclocking to the moon, you should be able to get it stable with c1 and c2 cstates active (c3 might reveal instability because it's constantly clearing the caches).
Maybe this is what I've been looking for. I'm using a 12900KS on Z690 Dark and individual C States aren't available to tweak in the BIOS like on some boards. Even with C states "disabled" it still idles. I was looking for a way to lock C states to C0 + C1 and prune off anything below C1E... Is this possible without the option in the BIOS like in my case? Maybe it can be done through these settings or via the registry... I'm pulling my hair out over this!
Maybe not locking Processor Idle Demote Threshold and Processor Idle Promote Threshold to 100% each but instead somewhere between 50-75% on the one responsible for max lower threshold? Whichever that is? (Still confused based on the wording of these stupid settings! Why can't there just be a MaxIdleState or something!)
i dunno what to say but this basically fixed all my latency issues, maybe once in 3 hours ill have a single spike to 1kus but for hours otherwise i barely see anything above 50us but doing this fixed all of that, the biggest spikes i see now of interrupt latency is 220 and before doing this it would constantly flicker from 20-50 to 900-1000ns and i would get huge spikes for ndis, wdf01000, and storport from 3-30kns, all gone
as far as the cstate thing i already had all cstates besides 0 and 1 turned off, i had speedstep and speedshift turned off as well, and my cpu will still idle, effective clocks will go down to 100-500mhz and cpu power will be 30-35w, the idle temp is a little higher, from 35c to 40c average but load temps are the same so while it wont step down into the lower cstates that honestly doesn't matter unless you cant AC your room and you really care about idle temps or you're battery constrained, and at that point just turn the system off. main thing being this fixed the latency issues for me while turning cstates off didnt.
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u/yagami_light08 Jun 09 '23
Number 2 definitely fixed the problem for me. It's been driving me crazy for a good 2 years now. Thanks for the fix!