(4.14) kernel features talk

Test and fix the Kernel 4.14 features

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(4.14) kernel features talk

Unread postby back2future » Sun Jun 10, 2018 7:45 pm

Collecting experiences with current kernel features could be helpful, when compiling custom kernels and exceptional configurations.

CONFIG_BL_SWITCHER: Maybe not exactly suitable for userspace issues with mono ( related to big.Little arch: viewtopic.php?p=225228#p225228 ) only, but explains kernel features, that are not really commonly suitable for xu4 b.L cluster (even less for asymmetric? SoC's), when compiling a custom kernel and considering flexiblity or performance backup.
While running a 4.14.47 kernel with odroidxu4_kvm_defconfig there are 4 big cores slighly busy and 4 little cores almost not visible on idling.
With "#CONFIG_BL_SWITCHER¹ is not set" enabled, only 4 little cores @ highest 1.5GHz (odroid-cpu-control -l) with static cache line size ( __C__get_current_cpu_cache_line_size() ) were visible to a (lower performant) unix os at low demand.
It did not switch to higher frequencies or the 4 big cores (maybe configurable through echo "1" > /sys/devices/system/cpu/cpuX/online ^^ verify by cpufreq-info) at a kernel compiling performance situation.

Adding experiences for other kernel features would be interesting for many, compiling custom config kernels, we think. Thx.

( 1) was mentioned here for a 4.7.x configuration, same for 4.14 for xu4: viewtopic.php?p=148336#p148336 )
Last edited by back2future on Sun Jun 10, 2018 11:05 pm, edited 5 times in total.
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Re: (4.14) kernel features talk

Unread postby back2future » Sun Jun 10, 2018 8:10 pm

Has anyone ever tested a 4.14 kernel with CONFIG_LATENCYTOP enabled?
Booting stops after kernel is loaded by u-boot.
Difference between a proper 4.14 kernel are 3 dependencies for CONFIG_LATENCYTOP=y
CONFIG_KALLSYMS_ALL
CONFIG_SCHED_DEBUG
CONFIG_SCHEDSTATS

Code: Select all
CONFIG_LATENCYTOP:                                                                                                           
 │   │
 │   │ Enable this option if you want to use the LatencyTOP tool
 │   │ to find out which userspace is blocking on what kernel operations.
 │   │
 │   │ Symbol: LATENCYTOP [=n]
 │   │ Type  : boolean
 │   │ Prompt: Latency measuring infrastructure
 │   │   Location:                                                               
 │   │     -> Kernel hacking
 │   │   Defined at lib/Kconfig.debug:1574
 │   │   Depends on: DEBUG_KERNEL [=y] && STACKTRACE_SUPPORT [=y] && PROC_FS [=y]
 │   │   Selects: FRAME_POINTER [=n] && KALLSYMS [=y] && KALLSYMS_ALL [=n] && STACKTRACE [=y] && SCHEDSTATS [=n] && SCHED_DEBUG [=n]
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