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Scheduler Changes For Linux 5.15 - Still No Sign Of Any Intel Thread Director Optimizations

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  • sandy8925
    replied
    Originally posted by tildearrow View Post

    But AMD can do 64 cores with 280W...
    With low single threaded performance. All of those 64 cores are fighting for 280 W. They also don't run at the rated turbo frequency on a full load. With Ryzen, you're only guaranteed the base frequency on an all-core full load. And only one of the cores is actually guaranteed to reach the rate turbo frequency.

    So it's all luck of the draw with Ryzen, you don't know what you're getting, and where it will actually top out. You have to unlock limits, tune and tweak to actually get the full performance for your hardware.

    Also, just like Intel, that 280W TDP is only for an all-core full load at base frequency. It actually consumes more.

    For example, my 3900X is said to have 105W TDP, but that's only at base frequency of 3.8 GHz. Actual frequency at all-core full load is 4.05 GHz and that uses 142W. To actually unleash the full performance of the CPU, I have to unlock the TDP and current limits in the UEFI so that it can actually go higher (which means more power).

    AMD isn't as efficient as you think, and Intel isn't as bad as you think. There's just a lot of hyperbole from AMD fans, and shadows and curtains by AMD.

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  • smitty3268
    replied
    Originally posted by tildearrow View Post

    But AMD can do 64 cores with 280W...
    AMD's chips are more efficient, and Intel doesn't really care as long as they can retake the performance lead. Plus that's a server chip with lower single-threaded performance, so not exactly a fair comparison. The 5950X is still better, but more representative with 16 cores at 140 watts and it could use more than that pretty easily.
    Last edited by smitty3268; 30 August 2021, 11:31 PM.

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  • tildearrow
    replied
    Originally posted by smitty3268 View Post

    At 8p + 8e cores, that seems about right to me.

    Maybe 24w per performance core, and 6w per efficiency core, or something similar?

    Seems about right given what Intel has done the last few gens to try and keep up with AMD, and what we've seen from Intel's 10nm architecture so far in Tiger Lake. It's not exactly low power.
    But AMD can do 64 cores with 280W...

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  • smitty3268
    replied
    Originally posted by tildearrow View Post

    How could it be 250W?! A lot of cores I may understand, but otherwise... what?
    At 8p + 8e cores, that seems about right to me.

    Maybe 24w per performance core, and 6w per efficiency core, or something similar?

    Seems about right given what Intel has done the last few gens to try and keep up with AMD, and what we've seen from Intel's 10nm architecture so far in Tiger Lake. It's not exactly low power.
    Last edited by smitty3268; 30 August 2021, 11:05 PM.

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  • HEL88
    replied
    Intel makes it clear that desktop Linux is completely irrelevant.

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  • jaxa
    replied
    Originally posted by uid313 View Post
    The Alder Lake CPU is interesting because it has 8 powerful cores and 8 energy efficient cores for a total of 16 cores, so now desktop x86 has more cores than ever
    AMD already did that with mainstream Ryzen 9 3950X and 5950X CPUs.

    Originally posted by tildearrow View Post

    How could it be 250W?! A lot of cores I may understand, but otherwise... what?
    They are pushing it hard. Probably 5.3 GHz for the big cores, and 3.9 GHz for the small cores. That's high even for the small cores, as I'm seeing 3.3 GHz max for Tremont. This is also power draw typical of the flagship Core i9-12900K. Other Alder Lake CPUs will use less.

    It looks like AMD will also raise the TDP for CPUs on the AM5 socket. Instead of 105W for the 12-16 core parts, 120W for 12-core, 170W for 16-core. TDP is almost a marketing term but you can see where things are going. Chips auto-overclock themselves based on the cooling situation and can turbo higher for very brief intervals. If you can cool it, why not?

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  • zerothruster
    replied
    Originally posted by tomtomme View Post
    @waxhead: equal heat distribution?
    As I understand things, that was the original reason. But does it still make sense on desktop or laptop machines ? For big servers working flat out 247, perhaps (I have no idea). But on many zen2 (and apparently some lower-end zen3 cezannes, if what I read is correct) there is latency and cache change when changing to a different CCX. On a fast enough machine, it probably isn't measurable except in benchmarks, but it certainly looks weird when I watch 'top'.

    Leave a comment:


  • intelfx
    replied
    Originally posted by tildearrow View Post

    How could it be 250W?! A lot of cores I may understand, but otherwise... what?
    My 5950X system (overclocked the shit out of it, of course) routinely eats up to 270W when I'm compiling stuff on all cores.

    Leave a comment:


  • tildearrow
    replied
    Originally posted by uid313 View Post
    The Alder Lake CPU is interesting because it has 8 powerful cores and 8 energy efficient cores for a total of 16 cores, so now desktop x86 has more cores than ever and an interesting heterogeneous architecture similar to the ones long used in ARM processors on smartphones.

    But rumors is that Alder Lake is very power hungry, that it uses up to 250 W which is rather insane!
    How could it be 250W?! A lot of cores I may understand, but otherwise... what?

    Leave a comment:


  • ms178
    replied
    Maybe some CPU designs might benefit where the internal memory access is different, my Xeon 2678v3 is a great example where it is not 2 x 6 cores per memory bus but 1 x 8 and 1 x 4. That means that memory latencies are not the same for each core. The scheduler could favor the core complex which shares the same memory latencies for the workload which fits into a core complex.

    Leave a comment:

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