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Dolphin Issue 
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Joined: 2014-09-27 09:27
Posts: 2384
Location: Australia
 Dolphin Issue
While Dolphin is emulating a game the whole computer system exhibits big delays when reacting to my mouse inputs. For example: Clicking another program window to bring it in to focus will result in a 2 to 3 second delay before that program is brought in to the foreground and then that program is snappy to my inputs. Switching to another program will also incur a big delay after which that program becomes snappy to my input. Clicking back on to the emulation window that is displaying the running game software incurs a 2 to 3 second delay before the emulated game's window is brought in to the foreground. Clicking the emulator program's game list window incurs a 2-3 second delay (the emulated game doesn't stall during any of these "delay" periods). Performance in programs other than the emulated game's window, is also overall worse in general.

I tried using Task Manager to adjust the emulator's Process Affinity and prevent it from utilizing 2 Logical Cores/1 Physical Core, but the performance issue remained.

Strangely, disabling Hyperthreading completely fixes this strange delay phenomena. So it seems Dolphin is a clear example of a situation where Hyperthreading is counterproductive at its objective (perhaps Hyperthreading was resulting in a physical CPU Core being burdened with double the number of context switches per second? I've heard context switching is a task that desktop CPU's aren't very efficient at doing rapidly).

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2017-08-18 15:38
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Joined: 2014-09-27 09:23
Posts: 2201
Location: Germany
 Re: Dolphin really hates Hyperthreading
It's not an issue of RAM usage?

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2017-08-18 15:58

Joined: 2014-09-27 09:27
Posts: 2384
Location: Australia
 Re: Dolphin really hates Hyperthreading
No, I have 24GB of RAM and 4GB of VRAM and the emulator barely uses VRAM and I doubt it gets anywhere close to 24GB RAM consumption. I could probably make a video showcasing the difference with and without Hyperthreading, at some point.

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Windows 10 Pro x64 | Intel Core i7 920 @ 3.6GHz | ASUS P6T Motherboard | 24GB 1140~MHz DDR3 RAM | MSI Geforce 1070Ti Gamer | Integrated Sound | Samsung 860 Pro 512GB SSD | Corsair AX760 Power Supply | Fractal Design Define R5 PC case


2017-08-18 16:01
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Joined: 2014-09-27 09:21
Posts: 1550
Location: 日本
 Re: Dolphin really hates Hyperthreading
If we combined both your theories, it could be a layer 2 cache issue?

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2017-08-18 16:04

Joined: 2014-09-27 09:27
Posts: 2384
Location: Australia
 Re: Dolphin really hates Hyperthreading
Please explain what you mean by Layer 2 Cache issue. Do you think the amount of L2 cache on my CPU was insufficient?

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2017-08-18 16:39
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Joined: 2014-09-27 09:21
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Location: 日本
 Re: Dolphin really hates Hyperthreading
It might be a case that the two threads are not only sharing one core, but also it's layer 2 cache. If you disable hyperthreading, then each gets individual core and cache.

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2017-08-18 16:41

Joined: 2014-09-27 09:27
Posts: 2384
Location: Australia
 Re: Dolphin really hates Hyperthreading
That suggestion doesn't surprise me, I actually mentioned the cache as a possible culprit when asking about a different performance issue in Dolphin on their forum. Specifically: Performance in Super Mario Sunshine plummets from a constant 60FPS down to a constant 19FPS when Internal Rendering Resolution is increased from Native to 3x.

Increasing Internal Native Rendering Resolution to 3x cripples performance even though the CPU Core's and GPU never peak at 100% utilization, in fact the CPU Core's never exceeded 60% utilization and the GPU never exceeded 86% utilization.

These results are with Hyperthreading disabled and my CPU overclocked to 3.42Ghz, the phenomena mentioned in the original post occurs without overclocking.

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2017-08-18 16:47
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Joined: 2014-09-27 09:21
Posts: 1550
Location: 日本
 Re: Dolphin really hates Hyperthreading
Ooh, that should increase performance on my machine. Thanks for the info.

EDIT: Awesome! With my FX 8350 @ stock and GTX 760, I'm getting full speed on every game I've tried! I wonder what will happen when I overclock....

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2017-08-18 16:53

Joined: 2014-09-27 09:27
Posts: 2384
Location: Australia
 Re: Dolphin really hates Hyperthreading
It looks like the strange phenomena in the original post is only resolved by disabling Hyperthreading, if you are CPU performance bound. Overclocking allows multi-tasking performance to remain snappy while Hyperthreading is enabled.

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2017-08-19 03:25
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Joined: 2014-09-27 09:22
Posts: 5157
Location: A chair.
 Re: Dolphin really hates Hyperthreading
Franpa wrote:
It looks like the strange phenomena in the original post is only resolved by disabling Hyperthreading, if you are CPU performance bound. Overclocking allows multi-tasking performance to remain snappy while Hyperthreading is enabled.
That makes sense. The closer you are to full-power, the less hyperthreading is going to help and the more likely it is to just get in the way.

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2017-08-19 05:30
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