Syria oddities! Dropping frames even on menus

[edmuss]

I'm currently trialing the syria map for performance before I pull the plug, I know it's reputed to be hard on systems to being able to demo is awesome!

As a quick and dirty benchmark I have a mission setup where I drop down over Beirut from the north, skimming over the city at roof level and following the main road out to the airport.

My normal settings for Caucasus started off at 18ms and dropped to around 26 at roof height, this was ok until it started dropping frames, fpsvr graph is purple interspersed with green (around 28ms) and fps has dropped to about 18.  Obviously motion smoothing is long out the window and it's janky as hell.  However it would not stop dropping frames, even if I flew away from the city, exited the mission and it's still dropping on the main menu at <6ms frametime.  Only way to get rid of the purple is to restart dcs.

Fiddled about with the settings reverting from vr preset baseline and found out that running textures high causes it but running medium doesn't, (I can run terrain textures high with only 1ms or so drop and it makes the building pop in much more palatable) same nominal vram usage between the two and no more than Caucasus uses at the same settings 7.5-7.8 GB.  In fact I now have everything on high except textures/shadows/water/clouds which are on medium and I can still get 24ms with full smoothing and no frame drops.  Flying treetops in the valleys with full trees is glorious and still getting 18-22ms. Went up to 33k and it's getting around 15ms frametimes.

Anyone got any clue as to what's causing the framedrops with high textures specifically or is it a case of just running out of vram?

Running the reverb at 100% @60hz, PD1.0 with Kegtys shaders (apart from simple glass) and openvrfsr@0.67 renderscale.

edit: ran a similar test over Damascus and it was sitting between 24 and 28ms but didn't drop any frames with textures on medium and was smooth; set them to high and purple all over again, continuing into the menu after exiting the mission.

edit again: checked the Nvidia control panel and noticed that high power mode wasn't enabled, hasn't helped with the dropped frames with high textures but has gained about 4ms on frametimes for the same settings

Also tested without openvrfsr and it's much the same frametimes, however in doing so I've lost the sharpen filter which if I have to run medium textures helps a bit with some of the switch text. May just run far at 1.0 and hope the sharpen filter is worth the GPU overhead.

Edited December 21, 2021 by edmuss