stm32mp1 spi transaction slow down main application

[Ara.1]

Hi All

I have disabled the second core to validate one of old product, which runs on single core,

and same application cpu usage i have seen is 90-95 %

and same application runs and does the same spi transaction, i am seeing the cpu usage is 57%

all constraint are same except the core

following is the top of stm32mp1

top - 04:18:53 up 37 min, 1 user, load average: 1.70, 1.65, 1.51

Tasks: 107 total,  4 running, 103 sleeping,  0 stopped,  0 zombie

%Cpu(s): 4.5 us, 93.4 sy, 0.0 ni, 1.5 id, 0.3 wa, 0.0 hi, 0.3 si, 0.0 st

   9 root     20  0      0     0     0 S  2.3  0.0  0:05.56 ksoftirqd/0                                                              

  78 root     20  0      0     0     0 I  1.6  0.0  0:03.88 kworker/0:2-pm                                                           

 768 root     20  0   4556  1544  1204 R  1.0  0.2  0:01.27 top                                                                      

 612 root     20  0 113608  6668  4068 R 57.6  0.7 21:52.52 pxl                                                                      

  78 root     20  0      0     0     0 I 16.8  0.0  1:44.42 kworker/0:2-pm                                                           

  63 root     20  0      0     0     0 S  8.2  0.0  2:43.77 spi1                                                                     

  62 root    -51  0      0     0     0 S  7.4  0.0  2:30.84 irq/30-44005000                                                          

 9137 root     20  0      0     0     0 I  2.4  0.0  0:01.96 kworker/0:0-pm                                                           

  10 root     20  0      0     0     0 R  0.6  0.0  0:10.91 rcu_preempt                                                              

 768 root     20  0   4556  1544  1204 R  0.6  0.2  0:18.68 top                                                                      

   9 root     20  0      0     0     0 R  0.3  0.0  0:10.92 ksoftirqd/0     

what am observing , is that the SPI irq is running with very high priority -51, which makes our APP(pxl) deviates from cpu usage from 90 to 57,

is there any solution, to get pxl use cpu 90-95%

[Olivier GALLIEN]

Hi @Ara.1​ ,

Sorry it's not clear.

Do you mean that you application pxl is not working properly ?

CPU usage is not meaningful as such.

What was the old core performance ? ( mips, frequency )

Olivier

[Ara.1]

application $APP is working for the number of while (1){} ,

number of execution rate per sec are reduced when spi in action,

[Ara.1]

if we increase the nice the normal thread

 63 root     25  5      0     0     0 S  8.2  0.0  1:19.19 spi1 

spi normal thread...

this brings back $APP normal.

root@mp1som:~# top

top - 02:54:47 up 17 min, 1 user, load average: 2.01, 1.99, 1.44

Tasks: 110 total,  3 running, 107 sleeping,  0 stopped,  0 zombie

%Cpu(s): 4.6 us, 93.8 sy, 0.0 ni, 1.0 id, 0.3 wa, 0.0 hi, 0.3 si, 0.0 st

MiB Mem :   935.4 total,   810.0 free,    47.7 used,    77.6 buff/cache

MiB Swap:     0.0 total,     0.0 free,     0.0 used.   852.2 avail Mem

 PID USER     PR NI   VIRT   RES   SHR S %CPU %MEM    TIME+ COMMAND                                                                  

 540 root     20  0 113636  6744  4176 R 64.7  0.7 10:56.47 pxl                                                                      

  62 root    -51  0      0     0     0 S 12.1  0.0  1:57.49 irq/30-44005000                                                          

  63 root     25  5      0     0     0 S  8.2  0.0  1:19.19 spi1                                                                     

  23 root     20  0      0     0     0 I  6.9  0.0  0:29.57 kworker/0:1-pm                                                           

 3289 root     20  0   4556  1604  1264 R  1.0  0.2  0:03.61 top      

[Olivier GALLIEN]

Hi @Ara.1​ ,

Ok you application doing while (1) it take all remaining CPU and is a good indicator of CPU taken by other threads.

Anyway I don't get you last status :

"if we increase the nice the normal thread"

What do you mean ? Can you rephrase ?

Does this mean point is close ?

Thx

Olivier