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Hidden settings in Nvidia Inspector that reduce lag

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Hidden settings in Nvidia Inspector that reduce lag

Postby Vleeswolf » 20 Jun 2018, 15:59

Hi all,

I tried some (hidden) settings in Nvidia Inspector that appear to reduce input lag in the scenarios where you either let the frame rate hit and exceed the GSYNC limit (100 Hz in my case), or you use the Nvidia driver frame rate limiter accessible through Nvidia Inspector.

The settings are
"max_pending_command_buffers", which I have never seen mentioned before here. Default = no limit.
"Maximum frames allowed", which I have seen mentioned once before here, by RealNC. Default = 2.
"Maximum pre-rendered frames", well known setting, even available in Nvidia control panel. Default = app controlled.

With all three of these settings set to 1, input lag *seems* reduced from the defaults in cases I hit 100 fps and am capped by the GSYNC ceiling. Also when I limit frame rate to let's say 60 by using the driver frame rate limiter.

Edit:
the settings "Maximum frames allowed" and "Maximum pre-rendered frames" actually are the same thing, it seems. Nvidia Inspector just allows them to be set separately for some reason, however if you set "Maximum pre-rendered frames" in the Nvidia Control Panel, both settings are updated. The new setting that I believe improves input lag is then just "max_pending_command_buffers".

I'm lacking the hardware to test this for real. Except that I'm quite good at "feeling" the lag induced by limiting to 60 at defaults and using the TrackIR headset. Since TrackIR captures any head motion, any lag can be noticed rather easily. With the settings mentioned above all set to 1, lag feels almost absent, very similar to capping within game even.

[[Intermezzo: capping to 60 Hz, or an integer divisor of 120, is important for using TrackIR since its update frequency is 120 Hz, and smooth motion is impossible otherwise.]].

At this point I'm unable to provide more evidence. Perhaps someone with ready access to a high-speed camera and some interest in these settings could run a small test?

Cheers,
Vleeswolf
Last edited by Vleeswolf on 21 Jun 2018, 01:48, edited 2 times in total.
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Re: Hidden settings in Nvidia Inspector that reduce lag

Postby Sparky » 20 Jun 2018, 18:02

It's likely still better to just use a framerate cap to avoid hitting the max refresh rate.
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Re: Hidden settings in Nvidia Inspector that reduce lag

Postby Falkentyne » 20 Jun 2018, 20:07

All of those settings I believe are similar to "Prerender Limit" which is basically what you are changing.
It's questionable whether the old "Prerender Limit" was split up into mulitple settings or not, but this also used to be called "maximum frames allowed" in the old "Rivatuner" program (which was another name for Prerender Limit--at the time--we're talking about windows XP days here, maybe even windows 9X too).

The setting you see in the NVCP is similar to the old Prerender Limit, but the functionality may have been split up as I said before.
Back during the old days, using 60hz vsync on with the default prerender limit (may have been 2 or 3) gave MASSIVE input lag, and using a value of "0" removed virtually all of the non basic "16.7ms" input lag besides the normal frame lag. Some d3d games didn't start with a value of 0 at the time.

Starting with windows 7, the value "0" was removed and the lowest value became "1". Can't speak for anything else these days as I never even bother with it anymore. But AMD users still need to change this setting as some games were designed from "Flip Queue Size" value=3 (old default), and the newer default of "2" would cause some games to give strange erratic lag (I believe Path of Exile was one game which hated a value of 2).

Just like Nvidia, the old lowest value of 0 was removed from windows 7+ drivers.
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Re: Hidden settings in Nvidia Inspector that reduce lag

Postby Nawafwabs » 24 Jun 2018, 10:37

i cant find "max_pending_command_buffers" in nvidia inspector 2.13
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Re: Hidden settings in Nvidia Inspector that reduce lag

Postby Vleeswolf » 24 Jun 2018, 15:35

Nawafwabs wrote:i cant find "max_pending_command_buffers" in nvidia inspector 2.13


Latest is 2.1.3.20. Setting can be found under category "Extra" once you enable "Show unkown settings from NVIDIA predefined profiles" (the magnifying glass with gears icon in the toolbar).

After some further experimentation I'm not sure so that setting does much btw. It's mostly the setting "Max frames allowed" together with "Max prerendered frames". With Inspector you are able to set one and not the other, while the NVIDIA control panel sets both at the same time.
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Re: Hidden settings in Nvidia Inspector that reduce lag

Postby Falkentyne » 24 Jun 2018, 16:05

Vleeswolf wrote:
Nawafwabs wrote:i cant find "max_pending_command_buffers" in nvidia inspector 2.13


Latest is 2.1.3.20. Setting can be found under category "Extra" once you enable "Show unkown settings from NVIDIA predefined profiles" (the magnifying glass with gears icon in the toolbar).

After some further experimentation I'm not sure so that setting does much btw. It's mostly the setting "Max frames allowed" together with "Max prerendered frames". With Inspector you are able to set one and not the other, while the NVIDIA control panel sets both at the same time.


If they can be set separately, verify that one setting is NOT just for Open GL. and confirm by setting the highest possible value (usually a value of either 5 or 9) and test an OPEN GL game with VSYNC ON At 60hz refresh rate.

I remember back in the day, the Direct3D setting had no effect on Open GL at all. But the last time I tested that on an Nvidia card was ....uh...15 years ago ?
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Re: Hidden settings in Nvidia Inspector that reduce lag

Postby JoshPeterson654 » 09 Jul 2018, 04:11

Vleeswolf wrote: Perhaps someone with ready access to a high-speed camera and some interest in these settings could run a small test?


Vleeswolf


I'd find this really helpful as well. Thanks
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