Public bug reported:
While we are validating the FlexRAN on Ubuntu 20.04 with Low-Latency
kernel one of the long-run stability tests failed, looking for your
comments/support in understanding the problem. At this point, we
believe, some additional platform/OS level fine turning is required for
the flexRAN application to run stable (as you know flexran L1
application is very sensible to jitter and latency, hence we tried to
make sure flexran worker threads get highest priority, isolated cores,
irq isolation, etc.. ).
With Low-Latency kernel, FlexRAN short-term timer mode tests are passed.
But when we run oRAN mode test, flexran L1 application crashed with an
indication of - one of the worker thread was not able to complete its
processing in a given time. This test was aimed for a long duration
(continuous until interrupted), goal is check for at least 12hr
stability. Failure was observed at random time periods: ~2hr, ~4hr,
~45min…
Our initial thoughts are some interrupt raised and pre-empted the worker
core for longer period of time.
Attached is the dmesg output
Machine config is:
Configuration
Comments
uname -a
Linux flexran-ubuntu 5.4.0-77-lowlatency #86-Ubuntu SMP PREEMPT Thu Jun
17 03:26:36 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Kernel command line
# cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-5.4.0-77-lowlatency root=/dev/mapper/ubuntu--vg-
ubuntu--lv ro maybe-ubiquity intel_iommu=on iommu=pt
usbcore.autosuspend=-1 selinux=0 enforcing=0 nmi_watchdog=0
softlockup_panic=0 audit=0 cgroup_disable=memory intel_pstate=disable
mce=off hugepagesz=1G hugepages=40 hugepagesz=2M hugepages=0
default_hugepagesz=1G kthread_cpus=0,20 irqaffinity=0,20 nohz=on
nosoftlockup nohz_full=1-19,21-39 rcu_nocbs=1-19,21-39 skew_tick=1
isolcpus=1-19,21-39
root@flexran-ubuntu:flexran-21.03#
Application core mask
0x1F0001F0
Cores: 4,5,6,7,8,24,25,26,27,28
CPU info
# lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
Address sizes: 46 bits physical, 48 bits virtual
CPU(s): 40
On-line CPU(s) list: 0-39
Thread(s) per core: 2
Core(s) per socket: 20
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Gold 6248 CPU @
2.50GHz
Stepping: 7
CPU MHz: 2500.301
BogoMIPS: 3200.00
Virtualization: VT-x
L1d cache: 640 KiB
L1i cache: 640 KiB
L2 cache: 20 MiB
L3 cache: 27.5 MiB
NUMA node0 CPU(s): 0-39
Vulnerability Itlb multihit: KVM: Mitigation: Split huge pages
Vulnerability L1tf: Not affected
Vulnerability Mds: Not affected
Vulnerability Meltdown: Not affected
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass
disabled via prctl and seccomp
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers
and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Enhanced IBRS, IBPB
conditional, RSB filling
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Mitigation; TSX disabled
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 art
arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid
aperfmperf 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 lah
f_lm abm 3dnowprefetch cpuid_fault epb
cat_l3 cdp_l3 invpcid_single ssbd mba ibrs ibpb stibp ibrs_enhanced
tpr_shadow vnmi flexpriority ep
t vpid ept_ad fsgsbase tsc_adjust bmi1
avx2 smep bmi2 erms invpcid cqm mpx rdt_a avx512f avx512dq rdseed adx
smap clflushopt clwb intel_pt
avx512cd avx512bw avx512vl xsaveopt
xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local
dtherm ida arat pln pts pku o
spke avx512_vnni md_clear flush_l1d
arch_capabilities
Irqbalence service is off
sysv-rc-conf --level 12345 irqbalance off
Flexran application (L1 and testmac) run on bare metal environment
No VM or Container
** Affects: linux-lowlatency (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "dmesg output"
https://bugs.launchpad.net/bugs/1938580/+attachment/5514894/+files/dmesg_output.txt
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https://bugs.launchpad.net/bugs/1938580
Title:
Ubuntu low-latency kernel 20.04 fails stability tests
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