Guide: DPC Latency

Just to say:

1. Hellbovine: this is awesome stuff! Thanks so much for sharing your knowledge.

2. This may be in the 'gaming lounge', but this info is also solid gold for anyone wanting to run low latency audio software such as Reaper, Ableton, Cubase, Pro Tools, etc.
 
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I thought I was having major DPC issues, LatencyMon was reporting over 100ms for the highest DPC time. But then I simply disabled Driver Verifier and it's fine now. Is that normal?
 
That's strange. Driver Verifier doesn't run by default, unless you or a driver package enabled it. Having it running would cause latency spikes since it's basically a kernel driver debugger, and has to snoop driver calls.
 
Thanks that makes sense, I did enable it without doing much research on what it's actually used for. I had been having driver issues recently and just thought it would be a good idea to verify them...
 
The general rule to live by if performance matters to an individual, is to know that more stuff enabled will almost always translate to performance loss. In the world of computers, if something is active it costs resources to maintain and introduces more opportunities to be exposed to bugs, while reducing available resources to other software, such as drivers and games, which manifests as poor latency, frame rates, crashes, etcetera.

Optional things like the driver verifier fall into the "Prevent Future Issues" section of this guide, where I discuss how people tend to install unnecessary stuff after optimizing their Windows and it can quickly spiral out of control, causing substantial issues. Think about it like a multitasking human brain--the more tasks someone is given to perform at once the more exhausting it becomes, while increasing the odds of mistakes and failure.
 
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Has anyone tried disabling energy-saving strategies and fast storage technologies for solid-state drives? My Asus motherboard defaults to enabling fast storage. I think it's very useful.
 
Does the list in Step 4 have what you're referring to? If not, can you provide specific names of the settings please, or motherboard model so I can view its manual. I'm not sure what "Fast Storage" is, probably due to translation, and the closest thing I can think of is "Fast Startup" which is an option in the Windows control panel for power plans. Maybe you mean Rapid Storage Technology (RST)?
 
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Hellbovine said:
I discuss many BIOS options in Step 4 of the guide. Does that list have what you're referring to? If not, can you provide specific setting names please, so we know exactly which ones you meant.
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These two items may be helpful because I disabled them and I'm not sure if they are correct.
Intel Rapid Storage it in the BIOS settings, and several of my Asus motherboards, both new and old, are enabled by default and changed back to the default archi mode.
I don't think it's necessary to turn on energy-saving for solid-state drives, only mechanical hard drives do.
powercfg -attributes 0012ee47-9041-4b5d-9b77-535fba8b1442 0b2d69d7-a2a1-449c-9680-f91c70521c60 -ATTRIB_HIDE
powercfg -attributes 0012ee47-9041-4b5d-9b77-535fba8b1442 dab60367-53fe-4fbc-825e-521d069d2456 -ATTRIB_HIDE
powercfg -attributes 0012ee47-9041-4b5d-9b77-535fba8b1442 d639518a-e56d-4345-8af2-b9f32fb26109 -ATTRIB_HIDE
powercfg -attributes 0012ee47-9041-4b5d-9b77-535fba8b1442 fc95af4d-40e7-4b6d-835a-56d131dbc80e -ATTRIB_HIDE
 
Hellbovine said:
I'm not sure what "Fast Storage" is, probably due to translation, and the closest thing I can think of is "Fast Startup"
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It's not a quick start, it's RSP. The motherboard is z690-p, which is enabled by default and needs to be manually turned off. It is not a Windows power plan, it is not displayed by default and needs to be enabled with a command in the advanced power settings.
I heard that RST can cause a blue screen, but I haven't encountered it before, I just disabled it. Because I didn't install the RST driver, it kept popping up asking me to install the driver. That's why I turned it off, I don't know if it should be turned off.
 
I've never been a fan of Rapid Storage Technology, and I've mostly seen the same sentiment echoed from the masses. It's been a confusing topic for a long time, because it eventually evolved to have extra side features added, such as caching you mentioned, but that is a mess too, since they depend on certain combinations of motherboards, processor brands and generations, BIOS versions, Windows, and drives. Any performance differences seen are probably only due to RAID setups, which is more about hardware. Unless using RAID, it's generally left alone or disabled.

For your batch file, Link Management energy savings is mentioned throughout my guides and does affect performance. When a device is powered down into a lower functioning state or put into any form of sleep, it takes additional time for it to reach full power again and that adds DPC latency. Things like C1E (Enhanced Halt State) for example, will constantly have Windows reduce a processor's speed, even during intense gaming.
 
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I accidentally saw information about Intel TSX. I specifically checked it.
www.intel.cn

面向英特尔®处理器的英特尔® Transactional Synchronization Extensions...

使用英特尔平台更新 2021.2 或更高版本英特尔® Transactional Synchronization Extensions内存和性能监控单元的行为变化
www.intel.cn www.intel.cn
It is explained as follows: "TSX is Intel's multithreading technology that can improve the multi-core scheduling efficiency of CPUs, but there are also security risks."
I don't know if this is helpful, as I also play GTA 5 and Watchdog 2, and I will have time to test them.
 
I don't have a CPU affected by TSX, but if someone does and can show me some credible benchmarks with it on/off and provide some background on the topic, I'll add it into the guide if it's a tweak worth using. Since I cannot test it myself though, I don't want to add it in case it's something that ends up being misunderstood, overhyped, or doesn't actually affect anyone anymore because it got patched. I find that those things tend to be the case for a lot of stuff when I do my own testing, so I don't want to contribute to internet misinformation by recommending things that may be snakeoil.
 
Hellbovine said:
I don't want to contribute to internet misinformation by recommending things that may be snakeoil.
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do your testing and publish your findings under the "this worked for me" banner then let users test and see if it works for them or not. i have tried various adanced settings from here and around the web(various tweak projects/sites) that havnt given me any noticable improvements. there might be improvements if i was a gamer or benchmarker but im not. let users decide what works for them.

i havnt noticed a difference having tsx enabled or disabled to be honest, only inspectre tells me there is.
 
luckscent said:
Will I lose performance or increase latency by using 2 SSDs instead of 1?
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I think this is a great question, with a few offshots that I've contemplated over the years too, but I never got around to testing it yet. I'll have to get back to you on this one, because I have some ideas that you got me thinking about, but I also see some challenges, so I'm unsure how it will go.

Personally, I use multiple drives at the moment, with C: drive having Windows and installed software, while D: drive has portable NTLite, tools, and my tweaking projects. This is all just for my conveinence though, so that my workspace is always ready to go even after a reformat.
 
The short answer is no.

SSD's are faster than HDD's. But accessing two SSD's at the same time isn't any more of a problem than accessing two HDD's at the same time. The long answer is very technical and you need to study OS design, but Windows itself doesn't add any extra latency by having multiple disks.
 
Hellbovine said:
I've never been a fan of Rapid Storage Technology,,,,, etc
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things take time to speed up. i set everything to always on, cpu to base clock(disable turbo) msi's and their priorities to high.

what needs looking at is cpu power settings.
by importing "high performance(HP)" and "low latency(LL)" power plans and comparing with MBK1969's Power Setting Explorer you can usually tell what needs to be increased or decreased but with the LL plans(in particular) some will say that setting X is increased while others say that it should be decreased - c'mon guys, what is it, up or down ffs? you all claim to be LL, you cant all be right surely?

windows own power plans and their settings appear in multiple locations in the registry - search and see View attachment 12264
 
Clang2 said:
AHCI v NVME
View attachment 12261
get the best ssd you can afford. i have been using crucial sata and nvme drives for a few years now and they are reliable.
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In case I use nvme SSD, I saw something about the number of PCIe lanes on the processor/chipset and if the power used for this second SSD would lack other components that could cause congestion. I don't understand the subject either. so you would have to make a calculation based on each processor. I use a "gamer" notebook.
 
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luckscent said:
...I don't understand the subject either. so you would have to make a calculation based on each processor...
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It's helpful to learn a little about white paper aspects, but honestly it's not that important, because what actually matters is how things behave in the real world, which usually differs from what developers and tech enthusiasts claim. That is why I test literally everything I can, because almost nothing ever works the way people say it does or should, since an alarming number of assumptions are made these days about computers, including by the developers themselves as they push untested updates built on assumptions, which is something I had to fight daily as a quality control lead.

Buying better hardware is of course good, and while that would benefit from some minor white paper knowledge, ultimately users just need to visit a few hardware review sites and cross reference the results to make sure nothing odd stands out. Then make purchases based on what the best performance per dollar is. I'd actually spend more time researching bugs associated with newer hardware to see if I'm setting myself up for a frustrating experience if I purchase that stuff, than I would spend investigating what a new "2.0 specification" means, for example.
 
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