Latency Measurements
####################
This benchmark measures the average latency of selected kernel capabilities,
including:
* Context switch time between preemptive threads using k_yield
* Context switch time between cooperative threads using k_yield
* Time to switch from ISR back to interrupted thread
* Time from ISR to executing a different thread (rescheduled)
* Times to signal a semaphore then test that semaphore
* Times to signal a semaphore then test that semaphore with a context switch
* Times to lock a mutex then unlock that mutex
* Time it takes to create a new thread (without starting it)
* Time it takes to start a newly created thread
* Time it takes to suspend a thread
* Time it takes to resume a suspended thread
* Time it takes to abort a thread
* Measure average time to alloc memory from heap then free that memory
When userspace is enabled using the prj_user.conf configuration file, this benchmark will
where possible, also test the above capabilities using various configurations involving user
threads:
* Kernel thread to kernel thread
* Kernel thread to user thread
* User thread to kernel thread
* User thread to user thread
Sample output of the benchmark (without userspace enabled)::
*** Booting Zephyr OS build v3.5.0-rc1-139-gdab69aeed11d ***
START - Time Measurement
Timing results: Clock frequency: 120 MHz
Preemptive threads ctx switch via k_yield (K -> K) : 519 cycles , 4325 ns :
Cooperative threads ctx switch via k_yield (K -> K) : 519 cycles , 4325 ns :
Switch from ISR back to interrupted thread : 508 cycles , 4241 ns :
Switch from ISR to another thread (kernel) : 554 cycles , 4616 ns :
Create kernel thread from kernel thread : 396 cycles , 3308 ns :
Start kernel thread from kernel thread : 603 cycles , 5033 ns :
Suspend kernel thread from kernel thread : 599 cycles , 4992 ns :
Resume kernel thread from kernel thread : 547 cycles , 4558 ns :
Abort kernel thread from kernel thread : 339 cycles , 2825 ns :
Give a semaphore (no waiters) from kernel thread : 134 cycles , 1116 ns :
Take a semaphore (no blocking) from kernel thread : 53 cycles , 441 ns :
Take a semaphore (context switch K -> K) : 689 cycles , 5742 ns :
Give a semaphore (context switch K -> K) : 789 cycles , 6575 ns :
Lock a mutex from kernel thread : 94 cycles , 783 ns :
Unlock a mutex from kernel thread : 24 cycles , 200 ns :
Average time for heap malloc : 620 cycles , 5166 ns :
Average time for heap free : 431 cycles , 3591 ns :
===================================================================
PROJECT EXECUTION SUCCESSFUL
Sample output of the benchmark (with userspace enabled)::
*** Booting Zephyr OS build v3.5.0-rc1-139-gdab69aeed11d ***
START - Time Measurement
Timing results: Clock frequency: 120 MHz
Preemptive threads ctx switch via k_yield (K -> K) : 1195 cycles , 9958 ns :
Preemptive threads ctx switch via k_yield (U -> U) : 1485 cycles , 12379 ns :
Preemptive threads ctx switch via k_yield (K -> U) : 1390 cycles , 11587 ns :
Preemptive threads ctx switch via k_yield (U -> K) : 1289 cycles , 10749 ns :
Cooperative threads ctx switch via k_yield (K -> K) : 1185 cycles , 9875 ns :
Cooperative threads ctx switch via k_yield (U -> U) : 1475 cycles , 12295 ns :
Cooperative threads ctx switch via k_yield (K -> U) : 1380 cycles , 11504 ns :
Cooperative threads ctx switch via k_yield (U -> K) : 1280 cycles , 10666 ns :
Switch from ISR back to interrupted thread : 1130 cycles , 9416 ns :
Switch from ISR to another thread (kernel) : 1184 cycles , 9874 ns :
Switch from ISR to another thread (user) : 1390 cycles , 11583 ns :
Create kernel thread from kernel thread : 985 cycles , 8208 ns :
Start kernel thread from kernel thread : 1275 cycles , 10625 ns :
Suspend kernel thread from kernel thread : 1220 cycles , 10167 ns :
Resume kernel thread from kernel thread : 1193 cycles , 9942 ns :
Abort kernel thread from kernel thread : 2555 cycles , 21292 ns :
Create user thread from kernel thread : 849 cycles , 7083 ns :
Start user thread from kernel thread : 6715 cycles , 55960 ns :
Suspend user thread from kernel thread : 1585 cycles , 13208 ns :
Resume user thread from kernel thread : 1383 cycles , 11525 ns :
Abort user thread from kernel thread : 2420 cycles , 20167 ns :
Create user thread from user thread : 2110 cycles , 17584 ns :
Start user thread from user thread : 7070 cycles , 58919 ns :
Suspend user thread from user thread : 1784 cycles , 14874 ns :
Resume user thread from user thread : 1740 cycles , 14502 ns :
Abort user thread from user thread : 3000 cycles , 25000 ns :
Start kernel thread from user thread : 1630 cycles , 13583 ns :
Suspend kernel thread from user thread : 1420 cycles , 11833 ns :
Resume kernel thread from user thread : 1550 cycles , 12917 ns :
Abort kernel thread from user thread : 3135 cycles , 26125 ns :
Give a semaphore (no waiters) from kernel thread : 160 cycles , 1333 ns :
Take a semaphore (no blocking) from kernel thread : 95 cycles , 791 ns :
Give a semaphore (no waiters) from user thread : 380 cycles , 3166 ns :
Take a semaphore (no blocking) from user thread : 315 cycles , 2625 ns :
Take a semaphore (context switch K -> K) : 1340 cycles , 11167 ns :
Give a semaphore (context switch K -> K) : 1460 cycles , 12167 ns :
Take a semaphore (context switch K -> U) : 1540 cycles , 12838 ns :
Give a semaphore (context switch U -> K) : 1800 cycles , 15000 ns :
Take a semaphore (context switch U -> K) : 1690 cycles , 14084 ns :
Give a semaphore (context switch K -> U) : 1650 cycles , 13750 ns :
Take a semaphore (context switch U -> U) : 1890 cycles , 15756 ns :
Give a semaphore (context switch U -> U) : 1990 cycles , 16583 ns :
Lock a mutex from kernel thread : 105 cycles , 875 ns :
Unlock a mutex from kernel thread : 17 cycles , 141 ns :
Lock a mutex from user thread : 330 cycles , 2750 ns :
Unlock a mutex from user thread : 255 cycles , 2125 ns :
Average time for heap malloc : 606 cycles , 5058 ns :
Average time for heap free : 422 cycles , 3516 ns :
===================================================================
PROJECT EXECUTION SUCCESSFUL
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