<p>The E7-4830v3 has 10 physical cores and 20MB of L3 cache. With two CPUs, you'd only have 20 physical cores and 40MB of L3. Since every thread is doing exactly the same thing, hyper-threading is virtually useless. It wouldn't help you anyway since you only have 2MiB per physical core and that's exactly what cryptonight requires.</p>

<p>So, short answer, with 40MB of L3 cache, you cannot run more than 20 instances of the cryptonight algorithm concurrently without dropping from L3 speed to RAM speed, which is a <em>huge</em> performance loss.</p>

<p>You can probably go higher than 10, but more than 20 is a non-starter.</p>

CC BY-SA 3.0
2017-10-03T04:42:06.470Z
So  that means i should be running 20 threads without any issues, but as soon as i increase more than 10 threads, the h/s starts to decrease.
Abdullah Khan
CC BY-SA 3.0
2017-10-03T04:43:26.153Z
For 20 threads , i am getting 4 h/s per thread.
Abdullah Khan
CC BY-SA 3.0
2017-10-03T04:45:37.997Z
What happens with 18 threads? And are you 100% sure you have two of them?
David Schwartz
CC BY-SA 3.0
2017-10-03T04:46:43.973Z
David Schwartz, for 18, i have 7 h/s on average
Abdullah Khan
CC BY-SA 3.0
2017-10-03T04:47:34.330Z
Hmm, now I see that it has 30MB of L3 cache and 12 physical cores. Maybe I looked up the wrong CPU. Yeah, it seems something is wrong. You should be performing better than that. Maybe you need a BIOS update? It may help to disable hyper-threading in the BIOS.
David Schwartz
CC BY-SA 3.0
2017-10-03T04:49:21.347Z
Could it be the issue with cpuminer-easy, that i am using?
Abdullah Khan
CC BY-SA 3.0
2017-10-03T04:50:09.750Z
I guess it could be. It couldn't hurt to try a different program.
David Schwartz
CC BY-SA 3.0
2017-10-04T09:46:09.197Z
The issue was with cpuminer-easy, i am currently using xmrig, and it is giving me about 700h/s for cryptonight.
Abdullah Khan
CC BY-SA 3.0
2017-10-04T17:56:07.830Z
That seems about right. I calculated 720 as about your maximum. (Using the numbers for the correct CPU this time.)
David Schwartz
CC BY-SA 3.0
2017-10-03T04:38:09.977Z
2017-10-03T04:38:09.977Z
David Schwartz
<p>I have dual xeon processors (total 48 cores). I am using cpuminer-easy with nicehash pool on fedora. I have noticed that if i keep my number of threads greater than 10, the h/s falls dramatically. I am using Cryptonight algorithm. For 40 threads, i get 2-3h/s per thread while with 10 threads i get 25 -30h/s per thread. What is wrong here? How can i utilize all cores?</p>

CC BY-SA 3.0
2017-10-03T04:19:39.177Z
What algorithm?
David Schwartz
CC BY-SA 3.0
2017-10-03T04:25:11.570Z
David Schwartz cryptonight
Abdullah Khan
CC BY-SA 3.0
2017-10-03T04:29:33.907Z
I think I know! What is the exact model of the CPUs?
David Schwartz
CC BY-SA 3.0
2017-10-03T04:35:10.960Z
David Schwartz Model name: Intel(R) Xeon(R) CPU E7-4830 v3 @ 2.10GHz
Abdullah Khan
<mining-hardware><cpuminer>
Why more threads reduce h/s rate?
Abdullah Khan
# Why more threads reduce h/s rate?

(Asked by: username_0 on 2017-10-03)

I have dual xeon processors (total 48 cores). I am using cpuminer-easy with nicehash pool on fedora. I have noticed that if i keep my number of threads greater than 10, the h/s falls dramatically. I am using Cryptonight algorithm. For 40 threads, i get 2-3h/s per thread while with 10 threads i get 25 -30h/s per thread. What is wrong here? How can i utilize all cores?

**Tags:** mining-hardware, cpuminer

> **Comments:**
> **username_1**: What algorithm?  
> **username_0**: username_1 username_1 cryptonight  
> **username_1**: I think I know! What is the exact model of the CPUs?  
> **username_0**: username_1 username_1 Model name: Intel(R) Xeon(R) CPU E7-4830 v3 @ 2.10GHz  

---

## 1 answers

### Answer by username_1 on 2017-10-03. Score: 1

The E7-4830v3 has 10 physical cores and 20MB of L3 cache. With two CPUs, you'd only have 20 physical cores and 40MB of L3. Since every thread is doing exactly the same thing, hyper-threading is virtually useless. It wouldn't help you anyway since you only have 2MiB per physical core and that's exactly what cryptonight requires.

So, short answer, with 40MB of L3 cache, you cannot run more than 20 instances of the cryptonight algorithm concurrently without dropping from L3 speed to RAM speed, which is a *huge* performance loss.

You can probably go higher than 10, but more than 20 is a non-starter.

> **Comments:**
> **username_0**: So  that means i should be running 20 threads without any issues, but as soon as i increase more than 10 threads, the h/s starts to decrease.  
> **username_0**: For 20 threads , i am getting 4 h/s per thread.  
> **username_1**: What happens with 18 threads? And are you 100% sure you have two of them?  
> **username_0**: username_1 username_1, for 18, i have 7 h/s on average  
> **username_1**: Hmm, now I see that it has 30MB of L3 cache and 12 physical cores. Maybe I looked up the wrong CPU. Yeah, it seems something is wrong. You should be performing better than that. Maybe you need a BIOS update? It may help to disable hyper-threading in the BIOS.  
> **username_0**: Could it be the issue with cpuminer-easy, that i am using?  
> **username_1**: I guess it could be. It couldn't hurt to try a different program.  
> **username_0**: The issue was with cpuminer-easy, i am currently using xmrig, and it is giving me about 700h/s for cryptonight.  
> **username_1**: That seems about right. I calculated 720 as about your maximum. (Using the numbers for the correct CPU this time.)  

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