Increased VRAM usage with Resizable BAR enabled in Cyberpunk 2077

[anything_taken]

Hi, everyone! I noticed a very strange effect after enabling Resizable BAR and running Cyberpunk 2077. Seems like the FPS didn't change, however in some scenarios game seems to work much smoother which is not shown on a frametime graph. Can't really explain it, but seems like in some scenarios camera rotation and fast movements are more responsive and look just smoother. However, it creates another problem - VRAM usage is around 700-800MB higher. I checked ReBAR ON and OFF several time to avoid error, and the effect was persistent.

For example in a scene where without ReBAR the game would use 9500-9700MB of VRAM it will start using 10200-10500MB (which means 12GB buffer of the RTX 4070 is actually full, since not only the game consumes VRAM). Higher VRAM usage creates a nasty effect which makes entering the map or player menu to drop in FPS for some time, and after some time FPS is restored. I like the effect ReBAR has on this game in terms of smoothness, especially in high demanding scenes, but the increased VRAM consumption absolutely ruins it for some locations and managing player's interface.

I'm wondering how ReBAR is related to VRAM usage? I know it facilitates GPU and CPU communication, allowing to transfer larger assets at one piece. But it shouldn't affect the logic of VRAM usage. Am I missing something here? Why would game suddenly start to use more VRAM when I enable ReBAR? Are there some options in Nvidia Profile Inspector I could tweak to possibly fix this issue? I know there are two possible tweaks: rBar - Feature and rBar - Options, but I have no idea how they work and if they're useful in this case. Also, anyone else noticed that problem?

 

[eidairaman1]

Hi, everyone! I noticed a very strange effect after enabling Resizable BAR and running Cyberpunk 2077. Seems like the FPS didn't change, however in some scenarios game seems to work much smoother which is not shown on a frametime graph. Can't really explain it, but seems like in some scenarios camera rotation and fast movements are more responsive and look just smoother. However, it creates another problem - VRAM usage is around 700-800MB higher. I checked ReBAR ON and OFF several time to avoid error, and the effect was persistent.

For example in a scene where without ReBAR the game would use 9500-9700MB of VRAM it will start using 10200-10500MB (which means 12GB buffer of the RTX 4070 is actually full, since not only the game consumes VRAM). Higher VRAM usage creates a nasty effect which makes entering the map or player menu to drop in FPS for some time, and after some time FPS is restored. I like the effect ReBAR has on this game in terms of smoothness, especially in high demanding scenes, but the increased VRAM consumption absolutely ruins it for some locations and managing player's interface.

I'm wondering how ReBAR is related to VRAM usage? I know it facilitates GPU and CPU communication, allowing to transfer larger assets at one piece. But it shouldn't affect the logic of VRAM usage. Am I missing something here? Why would game suddenly start to use more VRAM when I enable ReBAR? Are there some options in Nvidia Profile Inspector I could tweak to possibly fix this issue? I know there are two possible tweaks: rBar - Feature and rBar - Options, but I have no idea how they work and if they're useful in this case. Also, anyone else noticed that problem?

Because rebar dumps everything at once from the cpu/ram into the gpu, its not a magic solution to performance gains as ymmv, maybe you should get a 16GB+ card

 

[anything_taken]

Because rebar dumps everything at once from the cpu/ram into the gpu, its not a magic solution to performance gains as ymmv, maybe you should get a 16GB+ card

Thank you for your reply! Do you know where I could read more cases about this scenario? I mean... I know that ReBAR enables to transfer larger chunks of data at once, but I still don't get why it should increase VRAM usage. The same amount of data should be just loaded in fewer transactions. At least this is what I have read in all discussions.

 

[Macro Device]

Imagine going from 1L bottles to 2 gallon canisters. It's hella handy when your peak load capacity is 4 gallons, you need less hands to do it. However, this leaves less flexibility. When it's only 9 litres you'll still need three canisters because...

Something similar is done by ReBAR. That's why you oftentimes have VRAM busy doing a whole lot of nothing whilst being in a "do not disturb" mode.

One of possible workarounds is simply overclocking VRAM with ReBAR turned off. I assume you're playing with RT enabled and this feature is really heavy on VRAM speed. The more the merrier. Just watch out, don't OC it too much.

 

[eidairaman1]

Thank you for your reply! Do you know where I could read more cases about this scenario? I mean... I know that ReBAR enables to transfer larger chunks of data at once, but I still don't get why it should increase VRAM usage. The same amount of data should be just loaded in fewer transactions. At least this is what I have read in all discussions.

Because you are pushing more data at once instead of it streaming in.