Poor mining performence 3990x
**Describe the bug**
Running the application in linux I'm getting really poor performance with the 3990x. Any ideas why I'm getting half the reported hash rate as others on the benchmark site?


**specs**

Linux
Ubuntu Server 18.04 LTS
Kernel 4.15
RAM 3200MHz
CPU Ryzen Threadripper 3990X

**To Reproduce**
```bash
xmrig --bench 1M --randomx-1gb-pages
```

**Expected behavior**
Upwards of 50K hash rate.

See below for output after running the command. 

```bash
 * ABOUT        XMRig/6.9.0 gcc/7.5.0
 * LIBS         libuv/1.18.0 OpenSSL/1.1.1 hwloc/1.11.9
 * HUGE PAGES   supported
 * 1GB PAGES    supported
 * CPU          AMD Ryzen Threadripper 3990X 64-Core Processor (1) 64-bit AES
                L2:32.0 MB L3:256.0 MB 64C/128T NUMA:1
 * MEMORY       38.2/62.8 GB (61%)
                DIMM 0: <empty>
                DIMM_A1: 16 GB DDR4 @ 3000 MHz CMK32GX4M2E3200C16
                DIMM 0: <empty>
                DIMM_B1: 16 GB DDR4 @ 3000 MHz CMK32GX4M2E3200C16
                DIMM 0: <empty>
                DIMM_C1: 16 GB DDR4 @ 3000 MHz CMK32GX4M2E3200C16
                DIMM 0: <empty>
                DIMM_D1: 16 GB DDR4 @ 3000 MHz CMK32GX4M2E3200C16
 * MOTHERBOARD  ASUSTeK COMPUTER INC. - PRIME TRX40-PRO
 * DONATE       0%
 * ASSEMBLY     auto:ryzen
 * POOL #1      benchmark algo auto
 * COMMANDS     hashrate, pause, resume, results, connection
 * OPENCL       disabled
 * CUDA         disabled
[2021-11-16 20:38:40.344]  bench    start benchmark hashes 1M algo rx/0
[2021-11-16 20:38:40.344]  cpu      use argon2 implementation AVX2
[2021-11-16 20:38:40.351]  msr      register values for "ryzen_17h" preset have been set successfully (7 ms)
[2021-11-16 20:38:40.351]  randomx  init dataset algo rx/0 (128 threads) seed 0000000000000000...
[2021-11-16 20:38:40.704]  randomx  allocated 3072 MB (2080+256) huge pages 100% 3/3 +JIT (353 ms)
[2021-11-16 20:38:41.683]  randomx  dataset ready (979 ms)
[2021-11-16 20:38:41.683]  cpu      use profile  rx  (128 threads) scratchpad 2048 KB
[2021-11-16 20:38:41.914]  cpu      READY threads 128/128 (128) huge pages 100% 128/128 memory 262144 KB (231 ms)
[2021-11-16 20:39:13.642]  bench    benchmark finished in 31.894 seconds (31353.9 h/s) hash sum = 898B6E0431C28A6B
[2021-11-16 20:39:13.642]  bench    press Ctrl+C to exit
[2021-11-16 20:39:13.732]  cpu      stopped (3 ms)
```