[LU-14584] LNet: 2 CPTs on a single NUMA node instead of one

Wed, 7 Apr 2021 18:59:03 +0000

By default, Lustre 2.14 LNet routers detect 2 CPTs instead of 1 CPT on a single NUMA node server. If not discovered, this could lead to very unbalance routers:

[root@sh02-oak01 ~]# cat /sys/kernel/debug/lnet/nis
nid                      status alive refs peer  rtr   max    tx   min
0@lo                         up     0    2    0    0     0     0     0
0@lo                         up     0    0    0    0     0     0     0
10.50.0.131@o2ib2            up     0 122544    8    0   128   127    40
10.50.0.131@o2ib2            up     0    1    8    0   128   127    57
10.0.2.214@o2ib5             up     0    2    8    0   128   128    75
10.0.2.214@o2ib5             up     0    2    8    0   128   128    70

The expected behavior is that LNet would instantiate only a single CPT if there is a single NUMA node available. More about such single NUMA node LNet router available below.

[root@sh02-oak01 ~]# lscpu 
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    2
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 79
Model name:            Intel(R) Xeon(R) CPU E5-2637 v4 @ 3.50GHz
Stepping:              1
CPU MHz:               1387.481
CPU max MHz:           3700.0000
CPU min MHz:           1200.0000
BogoMIPS:              6999.30
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              15360K
NUMA node0 CPU(s):     0-7
Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch epb cat_l3 cdp_l3 intel_pt ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm rdt_a rdseed adx smap xsaveopt cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts md_clear spec_ctrl intel_stibp flush_l1d


[root@sh02-oak01 ~]# ls -ald  /sys/devices/system/node/node*
drwxr-xr-x 4 root root 0 Apr  5 14:10 /sys/devices/system/node/node0


[root@sh02-oak01 ~]# numactl --hardware
available: 1 nodes (0)
node 0 cpus: 0 1 2 3 4 5 6 7
node 0 size: 65314 MB
node 0 free: 42722 MB
node distances:
node   0 
  0:  10 


[root@sh02-oak01 ~]# lctl get_param cpu_partition_table
cpu_partition_table=0	: 0 1 4 5
1	: 2 3 6 7

This is happening with a default libcfs configuration (no libcfs module tuning):

[root@sh02-oak01 ~]# cat /sys/module/libcfs/parameters/cpu_npartitions 
0
[root@sh02-oak01 ~]# cat /sys/module/libcfs/parameters/cpu_pattern 
N

Whamcloud Community JIRA

[LU-14584] LNet: 2 CPTs on a single NUMA node instead of one