Processors

[gwiesenekker]

Hi,

If you are running Linux on a 1950x I would appreciate it if you could post the MiB/sec results of the following commands:

sysbench --test=memory --num-threads=1 run

sysbench --test=memory --num-threads=2 run

sysbench --test=memory --num-threads=4 run

On my system the results are 6414, 2938 and 2142 so are decreasing, but they should be increasing, suggesting there is a problem with the memory access on my system.

Thanks,

Gijsbert

[gwiesenekker]

A comment in the memory benchmark from SiSandra 'We finally discover an issue – TR (just like Ryzen) memory latencies (in-page, random access pattern) are huge – almost 3x higher than Intel’s.' allowed me to find the root-cause: you have to set the thread affinity on 1950x! Here are 'sysbench --test=memory --num-threads=N run' results without and with setting the thread affinity. They speak for themselves:

$ sysbench --threads=1 --test=memory run | grep -i mib/sec

62991.16 MiB transferred (6297.75 MiB/sec)

$ sysbench --threads=2 --test=memory run | grep -i mib/sec

31019.36 MiB transferred (3101.29 MiB/sec)

$ taskset 0x3 sysbench --threads=1 --test=memory run | grep -i mib/sec

61560.52 MiB transferred (6154.75 MiB/sec)

$ taskset 0x3 sysbench --threads=2 --test=memory run | grep -i mib/sec

102400.00 MiB transferred (10305.26 MiB/sec)

Regards,

Gijsbert