Author Topic: xeon v4 cpus  (Read 55051 times)

2016-07-04, 18:34:27
Reply #60

fobus

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Is there a point to choose 18-cores (or 22-cores) CPU for render node? Will it use all 72 (88) threads in corona in real rendering process (not only in Benchmark application)? Or may be it will be better to use 14- or 16-cores CPUs (render noe PC)?

2016-07-04, 19:01:31
Reply #61

Juraj

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For node, you simply want the highest overall performance. The Xeon line-up is structured that there is never a model which has same performance at lower or higher-core count, it goes like sinusoid instead. Currently the highest-performance yielding models are the 20-22 (there is even OEM 24 version) cored ones.

For workstation though, it's worth sacrificing a little bit performance and go for the lesser cored, higher clocked versions for few reasons:

1) Avoid processor groups like plague. (Non-server) Software developers didn't get the memo Microsoft introduced such feature. Corona and Vray work fine though.
2) AVX under-clocking base-clock and turbo bins. AVX instructions further lower the base clock, which Xeons already have rather low, and even the turbo clock is lower in such case, doesn't make big difference for rendering but it could in some other cases.
3)The weird issue with metro start-up in Windows 10. I honestly have no idea what to do with this, but I didn't had much time to investigate yet. It's ok for node, but very problematic for workstation>
4)You want the highest turbo bins. Currently most of the line-up has pretty flexible and powerful turbo bins, so even the low-clocked Xeons can go from 2.6 into 3.5Ghz for single-threaded processes. These makes v4 Xeons excellent workstation CPUs. Certain ES/OEM versions don't have this ;- ) So unless you're buying "authentic" or latest QS release of CPU, don't use them as workstation.
 

Because of this, it almost doesn't matter what kind of Xeon clock you get, because the turbo is so flexible (this wasn't the case in previous generations). Higher clocked Xeons in v4 don't make better workstation, pretty much all the line-up works the same, although some go up to 3.8+ Ghz in single-core turbo bin. It's because of the above issues you want to avoid it for WS.
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2016-07-05, 06:01:31
Reply #62

fobus

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So it will not be a problem to use all 88 logical processors (in dual 22-core system) with Corona? No need to setup any sort of DR to use all threads or something else?

About AVX. Is it applicable only to Xeons v4 or every Intel CPU? I tested Corona benchmark with 2600k and 3930k and hasn't seen any sort of lowering frequency. Turbo Boost was used to rise frequency to max for all cores and I had no issues with it.

2016-07-05, 10:03:57
Reply #63

Ryuu

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Will it use all 72 (88) threads in corona in real rendering process (not only in Benchmark application)?

Corona benchmark uses the same code that is used for the actual rendering process (albeit slightly older because we don't update the benchmark that often).

I just tested this on 6900k and I'm getting 3.5 GHz in both Corona 1.3 benchmark and Cinebench R15. The CPU is rated at 3.2 GHz base frequency and 4 GHz single core turbo boost. This seems quite fine to me, nothing unexpected here.

2016-07-05, 10:20:49
Reply #64

fobus

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6900k has only 16 threads so it will be impossible to see more than one processor group in windows. So Turbo Boost is working as expected. My question is will Corona use more than one processor group if threads more than 64 present.

2016-07-05, 10:59:49
Reply #65

Ondra

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6900k has only 16 threads so it will be impossible to see more than one processor group in windows. So Turbo Boost is working as expected. My question is will Corona use more than one processor group if threads more than 64 present.

I feel that we need to make a clear statement because there is some FUD regarding Corona and processor groups.

YES, Corona can handle any number of threads in the system with no problems and with 100% efficiency

We tested it multiple times, and we have reports from multiple people that it works fine. You can even easily artificially create multiple processor groups on your system with less than 64 threads and see for yourself, if Corona or any other software can handle it (https://msdn.microsoft.com/en-us/library/windows/hardware/ff542298(v=vs.85).aspx), so go ahead if you have any doubts :D. There are apparently a shitton of problems when using processor groups, but Corona is not one of them ;)
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2016-07-05, 11:16:15
Reply #66

Ryuu

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6900k has only 16 threads so it will be impossible to see more than one processor group in windows. So Turbo Boost is working as expected. My question is will Corona use more than one processor group if threads more than 64 present.

Sorry, I though we were still on the topic of Broadwell clock frequencies when AVX is used.

Besides what Ondra said, you can also see the benchmark results for yourself: https://corona-renderer.com/benchmark

Windows by default assigns logical cores from one physical CPU to the same processor group, so a 2x22 core computer would end up with two groups of 44 threads each. If Corona was not properly managing threads across different processor groups, this computer would have the same result as 22 core computers, which is not the case.

2016-07-05, 11:20:45
Reply #67

Juraj

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I wrote that Corona (and also Vray from 3.3 service pack) works 100perc. with processor groups :- ).

Regarding AVX, this isn't Haswell-E/Broadwell-E  "issue", but Haswell-E/Broadwell-E Xeon E5 v3/v4 thing, apparently because of their tighter thermal design (see the picture I attached from Intel presentation). It's about 300Mhz difference in turbo-bin depending on individual chip, I couldn't find where Intel actually lists this info.
But it doesn't do any kind of havoc, this is just one of those 'potential' losses, these CPUS are still fast as f*** :- ). Like....really nice.
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2016-07-05, 11:23:10
Reply #68

Ondra

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I wrote that Corona (and also Vray from 3.3 service pack) works 100perc. with processor groups :- ).
I also wrote it many times, maru did, ryuu did, yet people still have doubts ;)
Rendering is magic.How to get minidumps for crashed/frozen 3ds Max | Sorry for short replies, brief responses = more time to develop Corona ;)

2016-07-05, 11:33:14
Reply #69

fobus

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Regarding AVX, this isn't Haswell-E/Broadwell-E  "issue", but Haswell-E/Broadwell-E Xeon E5 v3/v4 thing, apparently because of their tighter thermal design (see the picture I attached from Intel presentation). It's about 300Mhz difference in turbo-bin depending on individual chip, I couldn't find where Intel actually lists this info.
But it doesn't do any kind of havoc, this is just one of those 'potential' losses, these CPUS are still fast as f*** :- ). Like....really nice.

You mean that Turbo Boost can't boost from nominal base frequency or it will lower уму base frequency down? If I have 2699 v4 with 2.2GHz (2.8 all cores with TurboBoost) I will end up with 1.9GHz lowered CPU in Corona? Or it will boost it to 2.5 only (2.8GHz -300MHz)?

I wrote that Corona (and also Vray from 3.3 service pack) works 100perc. with processor groups :- ).
I also wrote it many times, maru did, ryuu did, yet people still have doubts ;)

Sorry... I got it now. Great, but not for AVX.

2016-07-05, 11:42:03
Reply #70

alexyork

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Conclusion seems to be that these latest 18-core+ processors offer the expected rendering power and play perfectly nicely with Corona, but have major issues with Windows relating to Processor Groups, causing error messages, system slow-downs and requiring regular reboots, which is fairly crippling for workstation use.

So we're probably going to go with the latest v4 16-core (2697A-V4) to hopefully avoid this. We'll of course report here with results next week and will submit benchmarks for comparison. In theory they should offer basically identical performance to the 18-core 2697-V4.

Of course now with Brexit the pound/dollar is complete rubbish and the price of these things is through the sky...
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2016-07-05, 12:07:52
Reply #71

Juraj

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Regarding AVX, this isn't Haswell-E/Broadwell-E  "issue", but Haswell-E/Broadwell-E Xeon E5 v3/v4 thing, apparently because of their tighter thermal design (see the picture I attached from Intel presentation). It's about 300Mhz difference in turbo-bin depending on individual chip, I couldn't find where Intel actually lists this info.
But it doesn't do any kind of havoc, this is just one of those 'potential' losses, these CPUS are still fast as f*** :- ). Like....really nice.

You mean that Turbo Boost can't boost from nominal base frequency or it will lower уму base frequency down? If I have 2699 v4 with 2.2GHz (2.8 all cores with TurboBoost) I will end up with 1.9GHz lowered CPU in Corona? Or it will boost it to 2.5 only (2.8GHz -300MHz)?


Both (base-clock and turbo) are lowered. But because turbo kicks all the time (I consider turbo to be the "true" baseclock since you can't overclock them, well you "can" ...but, that's different topic)



But how much the pictured difference is depends on individual models, I can't find where Intel writes this. This is only for code that uses AVX.


Btw, Windows 10 doesn't require reboots. The issue is with single process that leaks after start menu usage, and simply needs to be restarted in task manager. That is still super annoying though. And processor groups sucks for non-aware apps ( Unreal 4 light baking sees only one....).
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2016-07-19, 08:43:28
Reply #72

fobus

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We've bought 20 Cores XEONs - all cores areused in rendering. It's good.
AVX is in use and lowering cores speed - it's bad.

2016-07-19, 10:45:15
Reply #73

Ryuu

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We've bought 20 Cores XEONs - all cores areused in rendering. It's good.
AVX is in use and lowering cores speed - it's bad.

Engineering samples usually have lower base & turbo frequencies and the frequency scaling may be even more drastic than what is seen in the production version.

2016-07-19, 12:41:09
Reply #74

fobus

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Yea. But it's still quite fast. Let's hope that we'll see AVX gone or will be used to increase speed instead of decreasing it.