Re: [dpdk-dev] Number of memory channels per processor socket?

[Keunhong Lee <dlrmsghd@gmail.com>]

See your motherboard spec.
For example, I'm using Intel 5930K with ASUS X99 Delux Motherboard (x99
chipset).
This site https://www.asus.com/us/Motherboards/X99DELUXE/specifications/
tells that
"Quad Channel Memory Architecture "
which means that "-n 4" is the correct configuration for me.

To fully use quad channel memory, I have to use 4 separated DRAM,
installed on different memory slots of my motherboard.

-n option optimizes memory bank access pattern for datastructures.
Since most motherboards support dual or quad memory channel,
-n 4 will work for most systems. (Only few motherboards support tri-channel
memory)

I hope that this information is useful to you.
Keunhong.



2015-06-28 18:54 GMT+09:00 Abhishek Verma <abhishekv.verma@gmail.com>:

> Hi,
>
> I am new to DPDK and i tried searching the archives in case this had been
> discussed but couldnt find any references and hence this email:
>
> What is the significance of " -n NUM: Number of memory channels per
> processor socket" which is passed as an EAL option? I have a virtual
> machine (VM) spawned using VirtualBox and i am trying to use DPDK to get
> faster access to packets there. I did lscpu, but that didnt give me
> anything interesting that i could use here:
>
> abhishekV@VirtualBox:~/dpdk/dpdk-2.0.0/x86_64-native-linuxapp-gcc/app$
> sudo
> lscpu
> [sudo] password for abhishekV:
>
> Architecture:          x86_64
> CPU op-mode(s):        32-bit, 64-bit
> Byte Order:            Little Endian
> CPU(s):                2
> On-line CPU(s) list:   0,1
> Thread(s) per core:    1
> Core(s) per socket:    2
> Socket(s):             1
> NUMA node(s):          1
> Vendor ID:             GenuineIntel
> CPU family:            6
> Model:                 58
> Stepping:              9
> CPU MHz:               2594.017
> BogoMIPS:              5188.03
> L1d cache:             32K
> L1d cache:             32K
> L2d cache:             6144K
> NUMA node0 CPU(s):     0,1
> abhishekV@VirtualBox:~/dpdk/dpdk-2.0.0/x86_64-native-linuxapp-gcc/app$
>
> I understand that i have two cores and hence should use -c 1 (since i have
> cores 0 and 1). However, i dont understand what to give as the "-n" option.
> Is it always 4?
>
> Thanks, Abhishek
>