Lockups: Finally found cause (and it's AH)

[humble]

Originally posted by SkyGnome
The only reasons that I've heard of NOT using vertical-sync is for benchmarking, and because some early games actually ran the physics differerently based on frame rate (early Quakes), which could give a player an advantage.  Otherwise, it just causes artifacts, and uses unneccessary CPU cycles.

Your not "using" CPU cycles...just GPU cycles. The game is chugging away regardless....from everything I can gleen AH is still very much a CPU dependent game...it will use all the CPU resources you have.....regardless of what you think your GPU is doing. Your GPU is not generating CPU cycles....its accepting output generated in real time BY the CPU. 99% of the time a later generation is waiting on a CPU output...thats why framerate in AH is more CPU dependent then VC dependent. It's capped by the CPU's ability to crunch all the numbers....not the GPU's ability to render the output. Anything that effects the effeciency of the CPU limits "thruput". The reason for V-sync is simply so your VC doesnt render frames your monitor cant display. If your VC renders 85 fps and your LCD can only display 60 then your dropping 25 fps of info (hit sprites etc) so you may appear to ghost shots or the other plane may appear to "miniwarp". This has no effect on your CPU cycles one way or the other. The CPU still calculates all the variables realtime regardless of what your VC configuration displays....

[SkyGnome]

Originally posted by humble
Your not "using" CPU cycles...just GPU cycles. The game is chugging away regardless....from everything I can gleen AH is still very much a CPU dependent game...it will use all the CPU resources you have.....regardless of what you think your GPU is doing. Your GPU is not generating CPU cycles....its accepting output generated in real time BY the CPU. 99% of the time a later generation is waiting on a CPU output...thats why framerate in AH is more CPU dependent then VC dependent. It's capped by the CPU's ability to crunch all the numbers....not the GPU's ability to render the output. Anything that effects the effeciency of the CPU limits "thruput". The reason for V-sync is simply so your VC doesnt render frames your monitor cant display. If your VC renders 85 fps and your LCD can only display 60 then your dropping 25 fps of info (hit sprites etc) so you may appear to ghost shots or the other plane may appear to "miniwarp". This has no effect on your CPU cycles one way or the other. The CPU still calculates all the variables realtime regardless of what your VC configuration displays....

Open your vid card control panel, select force vsync.

Pull up task manager, go to performance tab.

Run AH.  Sit in the tower with clipboard off screen.  Wait a bit.

Close AH, note level of CPU use on history graph.

Go to vid control panel, force no vsync.

Run AH again, etc.

As long as there's a decent delta between your sync'd and unsync'd frame rate, it's very clear from this that using vsync lets the CPU sleep a bunch.

It also makes sense if you actually know how this stuff works, and have actually written this sort of software, instead of just read 'net babble.

[humble]

Just as I expected there is no difference in CPU usage with V-sync on or off. In a properly configured system there wont be. If your getting anything different you have misconfigured your system.

I agree, it makes sense if you actually DO KNOW how this stuff works. V-sync has no bearing on CPU demand (at least as far as AH goes). I ran AH offline in the tower while doing this. That provides for a constant demand level...if you run it online you will get random variations due to enviornmental factors.

[bj229r]

If I need to know something about computers, I look to Skuzzy's opinion, if I need to know something about airplanes, I look to Widewing's opinion. No need to question eithers' conclusions. (If ya need to know ANYthing about ANYthing else, ask my wife, who apparently DOEs know it all)

[humble]

Originally posted by bj229r
If I need to know something about computers, I look to Skuzzy's opinion, if I need to know something about airplanes, I look to Widewing's opinion. No need to question eithers' conclusions. (If ya need to know ANYthing about ANYthing else, ask my wife, who apparently DOEs know it all)

I'm always amazed at folks arguing this stuuf with the guys who develop the game. On a broader basis however the reality is that the old "if a bear $%!^'s in the woods...." line means that the game modeled the smell even if no video card was around to "hear" it. The game (any similiar game) handles a tremendous volume of distinct objects. when a guy in a windmill fires of a round in TT its modeled regardless of if you can "see" it in your particular view orientation. Its trajectory is modeled and its impact is modeled and its crater is modeled...regardless of what your VC does. All your VC does is render that portion that you "see"....since you always have a view orientation that demand is relatively constant. The data stream relevent to that view is real time....not based on what you render. In effect the CPU is generating far more then you ever use.

The biggest "issue" right now is that the raw processing power of the GPU exceeds many CPU's and developers are trying to offload workload to the GPU from the CPU. The thought that your GPU is somehow "loading" your CPU is fundementally wrong....

[morfiend]

Originally posted by bj229r
If I need to know something about computers, I look to Skuzzy's opinion, if I need to know something about airplanes, I look to Widewing's opinion. No need to question eithers' conclusions. (If ya need to know ANYthing about ANYthing else, ask my wife, who apparently DOEs know it all)

 Ain't that the truth....amen bro:aok


 And I thought only my wife knew everything:furious

[jtdragon]

after the last update I have been having alot of lock-up's during the day, now to the point that I can not play in the day time. At night no problem.
My system had been runing great with everything max out.

[SkyGnome]

Originally posted by humble
I'm always amazed at folks arguing this stuuf with the guys who develop the game.  

I only argue with them when they are flat-out wrong.  And frankly, from reading his posts for several years, I really don't think Skuzzy has a very broad computer science or engineering background, or that he actually writes rendering code, at the very least.  This doesn't make him a bad resource on how to get AH running for you, of course.

Your screenies are unreadable due to your dual CPUs making the sum of the two CPUs difficult to interpret (and you can't use the percentage marker on the left, as when AH is alt-tabbed, it goes wild and pegs the CPU - which I wish they'd fix.)

Here's mine.  #1 is AH with Vsync on, pegged at 85fps, #2 is with vsync off, running around 120-150fps.  I also booted with /onecpu so that the graphs are readable.  Folks who doubt, try it for yourself - just make sure that you are running at settings that will allow a higher framerate with vsync off.




P.S. For a guy with "humble" as his name, you sure aren't!

[airhog99]

I run dual headed and can see my task manager while I'm using AH. My CPU load usually howers around 20-30% while I'm running the graphics at 60 fps. I know the graphics card can handle at least 120 fps (since it occasionally went up to that when the timing was screwed with Win2k and dual core).

This means that AH is neither CPU-bound, nor GPU-bound. AH is a relatively light application compared to many 3D programs nowdays.

As to why the CPU should be at 100% for things to be right, as someone claimed before, I just don't follow the reasoning behind that.

Run it on a slow CPU with a good graphics card, and it will be CPU-bound.
Run it on a fast CPU with a poor graphics card, and it will be GPU-bound.
Run it on a fast CPU with a good graphics card, and there will be free cycles in both processors.

[airhog99]

I just stumbled over this as I was googling for how to set vsync in the new driver:

Selecting Vertical Sync (vsync) from the NVIDIA Control Panel does not affect DirectX applications.
Due to architectural changes in the new Windows Vista Window Display Driver Model (WDDM), the graphics driver can no longer disable vsync from its own driver or Control Panel. Selecting this option from the NVIDIA Control Panel will have no affect on DirectX applications.

http://www.nvidia.com/object/vista_driver_news_022207.html

So if you use Vista and change vsync in the nvidia driver you won't be doing anything at all, it seems. (I use XP.)

[humble]

You can see the same type of varience (just look at CPU #2) in my system. No question that turning v-sync off creates a "table top" effect on CPU usage. However that doesnt change really change the base CPU demand IMO.

If we take 3 systems...

on a lower end system the graph will "flatline" either way since the CPU is running maxed out either way.

on your graph the CPU only tops out 20-25% of the time with V sync on, 100% with V-sync off....

on mine the system doesnt ever "top out" but overall thruput per cycle is higher with V-sync off...


my cpu line....




tried to duplicate what you had...

I havent played with other features to see what CPU varience is (i have everything at max) at default or various AA/AF settings high res...

This is the 1st system i've built that never maxes out running AH...I dont even stop anything and I can run anti virus etc in background with no performance hit. I have no arguement that additional GPU requests require more "work" per CPU cycles. However that work is minimal compared to the "base load". I dont feel your "saving CPU cycles" ever with AH. Is the workoad per cycle variable....sure. Does the configuration of your system and quality of your GPU effect the CPU workload....sure it does. I simply dont agree that your saving CPU cycles. No question your graph clearly shows a higher workload per cycle....in fact it looks like your CPU tops out 20-25% of the time with V-sync on and 100% with it off....

So with V sync off it certainly appears your system is CPU bottlenecked {with 1 processor running}...

[airhog99]

Oh, I found the setting for vsync in the new nvidia settings stuff, and with vsync off I get around 80-90 fps and the CPU howers around 50%. With vsync on I get 60 fps and the CPU howers around 30%. A significant difference, especially if you run a single core CPU system where one setting might eat all cycles wheras the other setting might leave 40% free for other things.)

I guess my 6800 GT, with every possible quality setting maxed, only does about 90 fps. I did notice tearing when running without vsync, and see no reason to not sync.

[airhog99]

humble,

What is "workload per cycle"?

P.S: Now AH has started to go unresponsive after Alt-Tab'ing out of it..
So anoying...

[humble]

Airhogg,

I'm not going to try and be what I'm not. So I'll try and explain my understanding...

A CPU can process a certain number of instruction sets. Anytime a CPU tops out at 100% its reached apoint that it is not handling the number of tasks it gets...so the process is CPU bottlenecked. When you reach that point you require more CPU cycles to acomplish a given task. Variable CPU workload under 100% simply means the CPU isnt being taxed to its maximim capacity...

The game still has to calculate all the information, which makes up a frame of data, regardless if it is displayed or not. You simply cannot stop doing real-time calculations

This is skuzzy's statement above, the CPU use by AH is constant regardless of framerate. Now video cards may or may not use CPU cycles to process frames. Each generation of GPU is more powerful and more and more is done on the VC. This is also specific (my understanding) to how the developer writes the code. The biggest potential benifit to a multicore CPU like the cell is that it can have anunlimited number (in theory) of proceccing elements. As it stands it has 1 true CPU and 8 processors that allow a program to assign tasks to each.

Your not saving anything specific to AH with V sync on or off. If you look at sky's system you can clearly see his CPU is capped out with V sync off...so no question he's putting a higher demand on the CPU....but that is coming from his VC....not from AH. (I have no clue what VC/drivers). I'm running a 7900GT with the recommended 84.66 drivers. I agree that v synch off tops your system off at its highest useage level (you can see he's also capped with it on...just not all the time). I dont think V-sync adds any additional overhead. My system never runs higher due to v-snyc...but it does run with a similiar table top....so no question even my GPU is using the CPU. Look at the #2 CPU and you'll see my "usage" with V-sync off is averaging 80% with little drop...on the v-sync on it tops at 80% but spikes down to 60%...

Your problem occures with V-sync on, which according to skygnome is less intensive. From my perspective your CPU's capacity is binary...it either can or cannot handle the load...anything less then 100% gives you seemless operation....once you bottleneck your system it cant handle the load and things wait in the que....

In every system I've ever had before AH ran at 99% CPU all the time. The goal was to stop as many other processes as possible so AH would process as much as it could in a CPU cycle.

[airhog99]

Most people really don't know what the heck is going on inside their computers, and I've seen a lot of weird statements here and elsewhere. Statement's that are more akin to old wife's tales than facts.

Now, when it comes to a "less than stellar grasp"...