processAffinityMask Testing

[Nellah]

I'm not very technical, but my brother put SET AffinityMask "80" into my Config after reading the guide what came up a week or so ago and my FPS went up slightly, something to do with running WoW from Core 2&3 but not 1(or something like that). If this makes any sense to you, hope it 'helped' in some way.

Just stood in Hyjal my FPS went from about 39-46 to 42-50ish(just stood still out of combat - not got a great PC) with nothing changing but that line into config.

What kind of CPU do you have? Need more info.

[Wries]

Hijacking thread posting my findings.

Hyper Threading Affinity testing

Hardware being tested
Intel SB Core i7 2600K 4.6 GHz
Corsair Dominator DDR 3 RAM 1600 MHz CL9
Nvidia Geforce GTX 460 1 GB - 800MHz Core, 2000MHz Memory


Software

*Adobe After Effects on (but no rendering while benchmarking unless said so)
*Adobe Photoshop (for screenshots)
*Chrome with 12 tabs open, I opened a lot of tabs featuring flash content, though paused all video playback on youtube tabs.
*Fraps, notepad, peerblock, msi afterburner and a couple of monitor gadgets running along.

What I call, THE ULTIMATE TEST OF DOOM

Test was done on Stormreaver EU with all graphical settings including shadows on ULTRA. Windowed mode (fullscreen) helps bringing down the FPS an extra notch.

I was standing near auction house facing the open world where the majority of players are jumping and flying around. Just around the time people get online for raid night. Want to really rape the processor here.

SET processAffinityMask "255" was set in config, afterwards I limited the usage of certain logical cores by doing it in windows task manager.


Test 1, Process Affinity set to 255, no interfering in task manager

Frames, Time (ms), Min, Max, Avg
2271, 60000, 33, 41, 37.850


As can be seen by the scrshot, wow has placed threads on all physical CPU's. The extra logical ones (the HT) don't get much to do though.


Test 2, Manually limiting the game to USE ONLY ONE LOGICAL CORE!

Frames, Time (ms), Min, Max, Avg
551, 60000, 8, 11, 9.183



Whew! WoW certainly needs to spread its threads!


Worth noting this is still better than my buddys Celeron D (which is a single core crippled Pentium 4) at 3.2 Ghz. He can't be in orgrimmar at all!




Test 3, Manually limiting the game to use two logical cores ON THE SAME PHYSICAL CPU, trying it to make some benefit from hyperthreading!

Frames, Time (ms), Min, Max, Avg
513, 60000, 7, 12, 8.550



I'm seeing some negative effect from HT here, but it could fall into the margin of error. In the task manager it certainly doesn't look like that the other logical core is being used.

With CoreAffinity set to 255 in config, WoW prefers using Core "7"(6) over Core "8"(7), but when I don't have CoreAffinity set to 255 in config it prefers the other and will absolutely refuse to use the seventh core unless I make it the only option. This goes for every physical core, without Core Affinity set to 255, wow seem to always have a logical core per physical that it absolutely doesn't want to touch! By default, WoW hates HT!

Test 4, Limiting WoW to only use two physical cores. NO HT!

Frames, Time (ms), Min, Max, Avg
2254, 60000, 34, 40, 37.567



Now this is interesting. Almost no difference vs 255. Those few Core2Duo owners that have achieved mind blowing clock speeds can rejoice. Well, in my testing environment at least. :P Mind you I'm letting other applications use the other cores.

Test 5, Limiting WoW to only use two physical cores but with HT cores around them being enabled as well.

Frames, Time (ms), Min, Max, Avg
2262, 60000, 34, 42, 37.700



It creeps from one logical CPU to the other occasionally. But nothing more.

Seem pretty clear to me that WoW doesn't care much about having two logical cores per physical. It will simply ignore one, regardless if you set Processaffinity to an eight core number or not.

HARDCORE TEST 1 with no relevance to anything really...: Capturing WoW Framerate while letting Adobe After Effects use 8 threads to render a semi-complex composition!

Frames, Time (ms), Min, Max, Avg
263, 20000, 8, 20, 13.150



Whew. No comments. Had to limit the test to 20 seconds because the composition was done then. Well.. 13 fps in orgr at peak time while rendering in after effects... an ok number!

I also wanted to do hardcore test no 2 and let After Effects render on one thread per core and let wow use the other thread per CPU, but it turned out After Effects didn't like my idea at all and disabled multithreaded rendering while I was sorting out its affinity.

Conclusion
WoW doesn't make any use of HT whatsoever.

[Cilraaz]

?

Post requires 10 characters but i have nothing more to say.

Gmail, Fmylife.com, Cinemassacre.com, 4 MMOC tabs, 2 guild site tabs, 3 tabs for numerous sites relating to an addon I author, and 6 tabs for my online D&D games. Those are stickied. That's 18. Then I usually have wow-professions.com, grooveshark.com, and one for random browsing.

@Wries: Interesting that you also noted no palpable difference in framerate between all cores enabled and core 1 disabled. I guess that theory is pretty much garbage now.

[nwo]

@Wries: Interesting that you also noted no palpable difference in framerate between all cores enabled and core 1 disabled. I guess that theory is pretty much garbage now.

I could see that theory being true in cases with much lower clocked CPUs, where the CPU usage would be much higher on the 2 primary cores (at least 90%). It obviously isn't true on high end, OCed CPUs which have more than enough power to spare.

[Deleted]

With CoreAffinity set to 255 in config, WoW prefers using Core "7"(6) over Core "8"(7), but when I don't have CoreAffinity set to 255 in config it prefers the other and will absolutely refuse to use the seventh core unless I make it the only option. [i]This goes for every physical core, without Core Affinity set to 255, wow seem to always have a logical core per physical that it absolutely doesn't want to touch! By default, WoW hates HT!

Technically - its Windows that decides which of the possible cores are actually utilized. Its default W7 behaviour consider non-physical cores 'low priority'. If you're loading either core to 100%, you're still making pretty much full use of that cores capabilities. SMT allows elimination of certain wait times between processing instructions to increase throughput efficiency, but actual processing capability is unchanged.

[Soisoisoi]

What kind of CPU do you have? Need more info.

Microsoft Windows XP 
AMD Phenom 8650 
Triple-Core Processor 
2.31 GHz, 2.00 GB of RAM

Hope this is what you need, as I said, not very good with PC stuff. :P

[Cilraaz]

I could see that theory being true in cases with much lower clocked CPUs, where the CPU usage would be much higher on the 2 primary cores (at least 90%). It obviously isn't true on high end, OCed CPUs which have more than enough power to spare.

The reason that it was assumed setting affinity away from core 1 would help is that other processes are already using core 1 (browser, vent, etc), as most of them aren't multi-threaded. If this were true, it would be true regardless of clock speed. CPU utilization as a percentage is a bad way to think of it. The core is either in use (100%) or not (0%). What you see in task manager is just a short-term average. If there were going to be any benefit to moving WoW away from core 1, it would happen regardless of clock speed.

[procne]

Kinda supports what I always thought, that WoW doesn't make any real use of multiple cores.

And HyperThreading? It's just very limited simulation of additional cores.

[Cilraaz]

Kinda supports what I always thought, that WoW doesn't make any real use of multiple cores.

And HyperThreading? It's just very limited simulation of additional cores.

Umm, all of the tests above actually refute the claim that WoW doesn't make use of multiple cores. Look at core usage in both my tests and Wries tests. Multiple cores with a fairly even load. Four cores at 40% usage are better than two cores at 80% usage, if you actually understand how CPUs work.

[Bloodmayj]

Umm, all of the tests above actually refute the claim that WoW doesn't make use of multiple cores. Look at core usage in both my tests and Wries tests. Multiple cores with a fairly even load. Four cores at 40% usage are better than two cores at 80% usage, if you actually understand how CPUs work.

Pretty much this, but apparently wow doesn't like non-physical cores. So anyone looking to get a rig solely for gaming probably would be better off with an i5 2500k than an i7 2600k.

[procne]

Umm, all of the tests above actually refute the claim that WoW doesn't make use of multiple cores. Look at core usage in both my tests and Wries tests. Multiple cores with a fairly even load. Four cores at 40% usage are better than two cores at 80% usage, if you actually understand how CPUs work.

Depends how you look at it. I just made a simple test - created app with single infinite loop and launched it. Usage of my CPU jumped on both cores. Does that mean I have created application that can utilise multiple cores? No. It only means that OS can switch single application between multiple cores to balance their heating.

Following this - does WoW really use all 4 cores? Or is OS merely switching it between those cores so that there is no single moment that WoW main thread is active on 2 cores? I don't want to see difference in loads. I want to see difference in framerates.

[nwo]

Following this - does WoW really use all 4 cores? Or is OS merely switching it between those cores so that there is no single moment that WoW main thread is active on 2 cores? I don't want to see difference in loads. I want to see difference in framerates.

Look at the results, there is no diference in fps using 2 cores versus using 4 cores.

[procne]

Look at the results, there is no diference in fps using 2 cores versus using 4 cores.

That's what I said in the beginning. Additional cores (above 2) don't seem to improve performance.
Wow has additional threads, but these are minor ones and handle things like sound. So second core might make a difference if single one cannot handle all those threads. But it is possible that even with single core might perform as well as 2, if only it's strong enough.

In fact I don't think there are many games that can utilise more than 2 cores, and for some time there won't be. Writing multithreaded application isn't easy, and sometimes performance gain might be smaller than additional load needed to synchronize threads

[Cilraaz]

Pretty much this, but apparently wow doesn't like non-physical cores. So anyone looking to get a rig solely for gaming probably would be better off with an i5 2500k than an i7 2600k.

As most of the forum long-timers have been saying since Sandy Bridge's release. The only question to that is the extra 2MB of L3 Cache. Some have said that the extra cache will help in WoW (or other CPU-bound games). This might be true, but the gains are hardly going to be worth the extra cost to the average gamer.

I don't want to see difference in loads. I want to see difference in framerates.

Four cores at 40% means that 40% of the time, each core is in use. Two cores at 80% means that 80% of the time, both cores are in use. Understanding that a CPU is binary (off or on) means understanding that a core can't actually be at 40% usage. It's used (100%) or not (0%). Having lower utilization over a period of time means that the core is available more often. At that point, there is less wait time when an instruction requests CPU. Wait time means lower framerate when it matters, such as a raid environment when the CPU is actually stressed.

Remember, these tests were done in Orgrimmar. One core vs two cores vs three cores vs four cores might look different in a raid setting. I'm just not comfortable asking my 24 guildmates to wait while I log out to change affinity values after every trash pack or boss. The only point of the test was to refute the claims of miraculous framerate gain by removing WoW from core 1.

That's what I said in the beginning. Additional cores (above 2) don't seem to improve performance.

If we want to get technical, you said "WoW doesn't make any real use of multiple cores", which would insinuate that a single core CPU should be sufficient for the game. This is known to be wrong.

Wow has additional threads, but these are minor ones and handle things like sound.

Actually, sound is one of WoW's larger threads.

[Wries]

Technically - its Windows that decides which of the possible cores are actually utilized. Its default W7 behaviour consider non-physical cores 'low priority'. If you're loading either core to 100%, you're still making pretty much full use of that cores capabilities. SMT allows elimination of certain wait times between processing instructions to increase throughput efficiency, but actual processing capability is unchanged.

I'm with you on that, and it was not what I was going for in your quotation. Technically there shouldn't be one core that is "more virtual" than the other. Both core 6 and 7 make up for one physical core and it shouldn't matter much which one of them that WoW decides to use.

But it seems like WoW makes the choice that Core 6* is bad and core 7* should be used (due to that they are both the same phys. core), so much in fact that without Affinity set in config, it would for me refuse to run threads on core 6 even if I only allowed it (through task manager) to make use of core 6 and not core 7 on that particular physical core. When affinity 255 is set through config.wtf, windows has no problems sending work over to core 6.

My conclusion was that it behaves differently without this line in config. It then seems to have some built-in "anti-HT". It "figures out" that there are virtual cores in the mix and decides that core w. x. y and z shouldn't be used at all, even if it doesn't get access to the other logical core.

Starting count on core 0 makes last core number 7

[procne]

Four cores at 40% means that 40% of the time, each core is in use. Two cores at 80% means that 80% of the time, both cores are in use. Understanding that a CPU is binary (off or on) means understanding that a core can't actually be at 40% usage. It's used (100%) or not (0%). Having lower utilization over a period of time means that the core is available more often. At that point, there is less wait time when an instruction requests CPU.

Wrong, there *may* be less wait time when a *process / thread* requests CPU. Instructions don't "request" CPU :S

Wait time means lower framerate when it matters, such as a raid environment when the CPU is actually stressed.

If we want to get technical, you said "WoW doesn't make any real use of multiple cores", which would insinuate that a single core CPU should be sufficient for the game. This is known to be wrong.

I said:
"Additional cores (above 2) don't seem to improve performance".
My idea is that main thread is handled by single core, while all other thread(s) are on the second core. With the second one not being fully used.

And still I stand by the fact that single core would be enough if it's strong enough and some additional factors are present (like frames limit from GPU).
But the main point is that imo there is single main thread in WoW and performance depends mostly on how well this thread can be processed. Multiple cores help nothing with this except for the fact that it may get its dedicated core which wouldn't have to be shared with other processes (thus no wait time). But with other processes using less than 5% of CPU it's not really a big difference.

Actually, sound is one of WoW's larger threads.

How do you know that?

[Wries]

And still I stand by the fact that single core would be enough if it's strong enough and some additional factors are present (like frames limit from GPU).

But what single core would that be? Running WoW on a single core on my 2600K resulted in a rather poor framerate when in a crowded orgrimmar with all settings on ultra.

Can't say to people looking to buy a new pc that they should wait until 2013 when a single core of a processor is strong enough!

[Cilraaz]

Wrong, there *may* be less wait time when a *process / thread* requests CPU. Instructions don't "request" CPU :S

Yeah, my terminology was slightly off. It's been known to happen.

I said:
"Additional cores (above 2) don't seem to improve performance".
My idea is that main thread is handled by single core, while all other thread(s) are on the second core. With the second one not being fully used.

And still I stand by the fact that single core would be enough if it's strong enough and some additional factors are present (like frames limit from GPU).
But the main point is that imo there is single main thread in WoW and performance depends mostly on how well this thread can be processed. Multiple cores help nothing with this except for the fact that it may get its dedicated core which wouldn't have to be shared with other processes (thus no wait time). But with other processes using less than 5% of CPU it's not really a big difference.

Or you may have said exactly what I quoted. You're also wrong on the single core idea. Sorry. Dual cores and better have been stomping single cores since TBC era when multi-threading was first introduced to WoW's code.

How do you know that?

An old blue post from before the battle.net changeover. Unfortunately, it was not one of the preserved posts.

[procne]

An old blue post from before the battle.net changeover. Unfortunately, it was not one of the preserved posts.

I only remember some blue post during TBC where player asked about multithreading in wow, and blue poster said that WoW wasn't coded with that in mind but they are going to move sound into separate thread and that it should be slight improvement on double core CPUs

But I digress. My main point was that above 2 cores there is not really any difference. Even if task manager shows that all cores work it doesn't mean those extra cores help. In fact, it may be misleading - task manager may show that all cores are used below 50% and still CPU may be not strong enough and will reduce framerates. Just because single core isn't strong enough to fully handle main thread

[Psilent]

Hey all,

I'm new to the forums, usually just read topics and don't post but this topic caught my attention and got me thinking about my own PC. I do not have the processAffinityMask line in my config file. Wondering if it will improve performance if I add that line into it. Here is my computer specifications.

Processor: Intel i7 Core 920 2.66 GHz Quad-Core
Video Card: ATI Radeon HD 5770
RAM: 6GB Triple Channel DDR3
Motherboard: ASRock X58 Extreme

When playing WoW I get about 40 FPS in Stormwind, but when I fly over Elywnn Forest/Ashenvale or Dragonblight the FPS drops to about 25 to 30. I don't do 25 player raids, but when I did in Wrath I'd get about 50 FPS during boss fights. In 10 player Cata raids I get 60 FPS during boss fights.

Anyway, after reading several articles and this thread I'm curious if I should add this line to my config file or just leave it be. Hopefully this isn't off topic, from the post. Just very interested in this thread and how it could effect my own game play experience.

Thanks