Linked by Thom Holwerda on Fri 18th Aug 2017 10:51 UTC
AMD

In this mini-test, we compared AMD's Game Mode as originally envisioned by AMD. Game Mode sits as an extra option in the AMD Ryzen Master software, compared to Creator Mode which is enabled by default. Game Mode does two things: firstly, it adjusts the memory configuration. Rather than seeing the DRAM as one uniform block of memory with an ‘average’ latency, the system splits the memory into near memory closest to the active CPU, and far memory for DRAM connected via the other silicon die. The second thing that Game Mode does is disable the cores on one of the silicon dies, but retains the PCIe lanes, IO, and DRAM support. This disables cross-die thread migration, offers faster memory for applications that need it, and aims to lower the latency of the cores used for gaming by simplifying the layout. The downside of Game Mode is raw performance when peak CPU is needed: by disabling half the cores, any throughput limited task is going to be cut by losing half of the throughput resources. The argument here is that Game mode is designed for games, which rarely use above 8 cores, while optimizing the memory latency and PCIe connectivity.

I like how AnandTech calls this a "mini" test.

In any event - even though Threadripper is probably way out of the league of us regular people, I'm really loving how AMD's recent products have lit a fire under the processor market specifically and the self-built desktop market in general. Ever since Ryzen hit the market, now joined by Vega and Threadripper, we're back to comparing numbers and arguing over which numbers are better. We're back to the early 2000s, and it feels comforting and innocent - because everyone is right and everyone is wrong, all at the same time, because everything 100% depends on your personal budget and your personal use cases and no amount of benchmarks or number crunching is going to change your budget or personal use case.

I'm loving every second of this.

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RE: Interesting
by dpJudas on Fri 18th Aug 2017 12:47 UTC in reply to "Interesting"
dpJudas
Member since:
2009-12-10

What really annoys me is that they essentially give you two shitty options: a default mode where they hide the NUMA setup to the applications and OS, or "Game Mode" where they disable half the chip.

It has actually caused me to think twice about buying a threadripper as I don't like hardware where I have to toggle between two modes as an end user. This solution sucks.

Reply Parent Score: 3

RE[2]: Interesting
by ahferroin7 on Fri 18th Aug 2017 13:00 in reply to "RE: Interesting"
ahferroin7 Member since:
2015-10-30

Entirely agreed. They'll be shooting themselves in the foot if they try this crap with the server/workstation options.

Reply Parent Score: 1

RE[2]: Interesting
by Alfman on Fri 18th Aug 2017 13:49 in reply to "RE: Interesting"
Alfman Member since:
2011-01-28

dpJudas,

What really annoys me is that they essentially give you two shitty options: a default mode where they hide the NUMA setup to the applications and OS, or "Game Mode" where they disable half the chip.

It has actually caused me to think twice about buying a threadripper as I don't like hardware where I have to toggle between two modes as an end user. This solution sucks.


Agree too. Any solution that requires rebooting is an awful solution. There should be no interruptions. Not only that but it shouldn't have to be a system-wide toggle ether. If a process doesn't cope well with NUMA, then it should be possible to switch the mode for individual processes independently from the rest of the system.

AMD's solution here certainly seems very odd. Unless the issues they're trying to work around are in the windows kernel itself? I don't know if it's the case, but it is a real possibility.

Not that this makes the options any less disappointing, however it would explain AMD's motivation for disabling NUMA at the system level rather than at the process level.

Reply Parent Score: 3

RE[3]: Interesting
by dpJudas on Fri 18th Aug 2017 14:03 in reply to "RE[2]: Interesting"
dpJudas Member since:
2009-12-10

Not that this makes the options any less disappointing, however it would explain AMD's motivation for disabling NUMA at the system level rather than at the process level.

I think their motivation is mainly to win benchmarks at any cost. By offering two modes they can always show the highest numbers that they can get.

I can certainly understand their motivation, but, as one that actually wanted to buy this chip, this really sucks because not even the default mode does the Right Thing(tm). Future applications do not have the ability to detect the NUMA layout and optimize for it, because even though I might be able to configure that in its control panel, the average end user does not know what all this stuff is. He will either keep it on default or select "Game Mode" because it sounds cool.

Bottom line I get from all this is that it makes no sense to write applications that take full advantage of threadripper. Ugh. And that's where my interest in this chip died. ;)

Reply Parent Score: 2

RE[3]: Interesting
by _txf_ on Fri 18th Aug 2017 14:34 in reply to "RE[2]: Interesting"
_txf_ Member since:
2008-03-17

AMD's solution here certainly seems very odd. Unless the issues they're trying to work around are in the windows kernel itself? I don't know if it's the case, but it is a real possibility.


If you read the article, they say that is precisely what it is.

Edited 2017-08-18 14:36 UTC

Reply Parent Score: 3

RE[2]: Interesting
by jing on Sat 19th Aug 2017 16:27 in reply to "RE: Interesting"
jing Member since:
2017-08-19

dpJudas,
If you were paying more attention to the reviews instead of getting annoyed you'd know that you can mix and match the options as you please.(idem for others who comment on the same lines)

It's well explained in the first Anandtech review. (http://www.anandtech.com/show/11697/the-amd-ryzen-threadripper-1950...)

The newest review happened because Anandtech misunderstood which flags defined the AMD game-mode.
(original review game-mode test had disabled SMT but retained all cores active with NUMA enabled)

Oddly "Anandtech game-mode" had better performance than the "AMD game-mode"... AMD probably made a power/performance trade-off here.

Mind that Threadripper is still an enthusiast thing!
And for a workstation is definitely better as-is (configurable via reboot) than a hypothetical "fixed" dual 1800X build.

Also is nice that if you wanted a 1800X with extra lanes: Threadripper game-mode delivers...

Edited 2017-08-19 16:28 UTC

Reply Parent Score: 1

RE[3]: Interesting
by dpJudas on Mon 21st Aug 2017 09:58 in reply to "RE[2]: Interesting"
dpJudas Member since:
2009-12-10

dpJudas,
If you were paying more attention to the reviews instead of getting annoyed you'd know that you can mix and match the options as you please.(idem for others who comment on the same lines)

I know I can do that. My primary point is that the default mode has NUMA disabled (as seen by the OS/applications), which means the apps have no chance of arranging their threads and memory accesses for maximum performance.

As this is a rather advanced subject, no enthusiast user is able to tell when to turn that on or off. You'd have to constant benchmark and reboot based on which application you are going to run. The only reasonable solution is therefore to pick one setting and stick to it.

There are basically three choices there:

1) Keep it at creator mode. This provides suboptimal performance for time critical things, as it is effectively rolling a dice where memory and threads will run.

2) Gimp it with the game mode. Probably the worst choice to pick.

3) Create a custom setup. Problem with this is that you will be the only user then with your particular setup - developers cannot target the setup directly as a result. If my threadripper is likely going to be the only one around with that particular setup, then I can no longer justify the development costs.

I like to treat my CPUs as fire-and-forget. That means this CPU must be evaluated as if I had it in creator mode. I get that not everyone will reach this conclusion, but that's how I look at it.

Reply Parent Score: 2