"Christmas - the time to fix the computers of your loved ones" « Lord Wyrm

The HPET bug: What it is and what it isn't

mat 26.04.2018 - 11:30 65597 38 Thread rating
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Lowprofile18

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Registered: Mar 2020
Location: USA
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Thank you @mat very informative if more questions arise i'll be sure to post here

Marctraider

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Registered: Feb 2020
Location: Nowhere
Posts: 6
New System (heavily tweaked), new results!

https://i.imgur.com/pzLGChh.png

mat

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Sexy. :)

Any tweaks that you want to share?

Marctraider

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Registered: Feb 2020
Location: Nowhere
Posts: 6
Well other than the general minimal LTSC and further neutered build, disabled all unnecessary junk, pcie root ports, asmedia and dozens of other options to minimize DPC latency, the major thing that dropped me from 6~ms max frametime spikes to 3ms~ was fooling around with ACPI/HPET Timer and some combination of useplatformclock/tick.

Strangely, achieving that 3~ms max frametime spike in this combination, has a negative effect of totally ruining MouseTester polling rates.

So one thing improves, mouse polling gets worse? How can that be explained :-/
Bearbeitet von Marctraider am 24.04.2020, 16:21

dxzdxz1

Bloody Newbie
Registered: Apr 2020
Location: Brazil
Posts: 2
I'm getting strange results depending on which monitor I use during the test.

I have a 27' 1080p Ultrawide Montior and a 55' 4k TV

On my TV the results are waaaaay diferent comparing to the monitor. On both I ran the test at 1920x1080.

I turned off Freesync on the monitor before the tests.

I made one test for each configuration:
HPET WINDOWS ON + UEFI ON
HPET WINDOWS ON + UEFI OFF
HPET WINDOWS OFF + UEFI OFF
HPET WINDOWS OFF + UEFI ON



I can't attach files here, so I uploaded the tests on zippyshare.

https://www28.zippyshare.com/v/XeGyj6ZS/file.html

Could you look at these results and see what's wrong?

Don't know if this is important, but on the TV my desktop scaling is 250 and on my monitor my desktop scaling is the default - 100.

Other thing you will notice, my GPU utilization at Fullscreen on the TV never gets above 91% and on Windowed varies between 80% to almost 100% depending on HPET ON or OFF.
On the other hand, running the test with my monitor, my GPU utilization is almost 100% in all tests.

I have a i7 3960X + 1070

dxzdxz1

Bloody Newbie
Registered: Apr 2020
Location: Brazil
Posts: 2
Sorry, I sent you the wrong link above.
The right one is this: https://www58.zippyshare.com/v/yOKUPvfG/file.html

falconepl

Bloody Newbie
Registered: May 2020
Location: Polen
Posts: 2
@mat Thanks for the app! TimerBench might be simple, but it's super useful for HPET performance analysis.

Just got one question. Is the Unreal demo used in the app available somewhere? Like the same version with the same camera motion as in the TimerBench, but as an Unreal project. I wanted to debug/profile CPU times in it to figure out what's responsible for that single ~20ms spike that I've got right at the beginning of every frame times analysis (right after the red part).
Bearbeitet von falconepl am 23.05.2020, 23:00 (minor edit)

mat

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Glad you like it!

The 20 ms seem to be part of the preloading. Probably a slower SSD in your system?
The first few seconds are ignored from each run to mitigate this preloading stuttering/slowdowns. A static time will never work out. Next version will add a loading screen for preloading.

Do you still need the Unreal project for the game test? It is available somewhere on the web.

falconepl

Bloody Newbie
Registered: May 2020
Location: Polen
Posts: 2
@mat Yeah, it could be the SSD. It's Samsung EVO, but I kinda suspect that it might have a faulty controller or something, because it also (very, very rarely, but still) freezes the whole system for some time when Steam initializes new game installation.

Yeah, if the demo is available anywhere I will surely take a look at it. I've found a demo scene already, but I wouldn't call it a benchmark, as it's just a "static" sample, without scripted camera motion.

By the way, have you considered open-sourcing TimerBench on GitHub or GitLab?
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