On 16.06.21 15:29, François Legal wrote: > Le Mercredi, Juin 16, 2021 11:40 CEST, Jan Kiszka <[email protected]> a > écrit: > >> On 16.06.21 11:12, François Legal via Xenomai wrote: >>> Le Mercredi, Juin 16, 2021 11:05 CEST, "Chen, Hongzhan" >>> <[email protected]> a écrit: >>> >>>> >>>> >>>>> -----Original Message----- >>>>> From: François Legal <[email protected]> >>>>> Sent: Wednesday, June 16, 2021 4:19 PM >>>>> To: Chen, Hongzhan <[email protected]> >>>>> Cc: [email protected] >>>>> Subject: RE: Large gpio interrupt latency >>>>> >>>>> Le Mercredi, Juin 16, 2021 10:10 CEST, "Chen, Hongzhan" >>>>> <[email protected]> a écrit: >>>>> >>>>>> >>>>>>> >>>>>>> -----Original Message----- >>>>>>> From: Xenomai <[email protected]> On Behalf Of François Legal >>>>>>> via Xenomai >>>>>>> Sent: Wednesday, June 16, 2021 3:16 PM >>>>>>> To: [email protected] >>>>>>> Subject: Large gpio interrupt latency >>>>>>> >>>>>>> Hello, >>>>>>> >>>>>>> working on a realtime data recorder (for which I submitted a patch to >>>>>>> add timestamp retrieval for net packets), I experience a strange >>>>>>> latency problem with taking GPIO interrupts. >>>>>>> >>>>>>> So basically my app monitors network packets (which as received by the >>>>>>> DUT would trigger toggling of a GPIO on the DUT) and one GPIO. >>>>>>> We know (from some ohter reference instrument) that the DUT would >>>>>>> toggle the GPIO 1-2ms after receiving a specific network packet. >>>>>>> >>>>>>> My recorder app relies on the timestamping of events done in interrupts >>>>>>> service routines for GPIOs and network interface. By checking the >>>>>>> timestamps returned by the application, I get an about 50ms delay >>>>>>> between the network packet and the GPIO (so something between 51 and >>>>>>> 52ms delay). >>>>>>> >>>>>> >>>>>> Are you toggling gpio and access gpio device through your rtdm device >>>>>> like on path /dev/rtdm/your_gpiocontroller/gpio*? >>>>>> >>>>> >>>>> Maybe my setup was not very clear. >>>>> I've got a DUT that receives network data, and toggles one of its GPIOs >>>>> depending one the network data. >>>>> >>>>> I've got another device running my realtime recording app, that receives >>>>> the same network data as the DUT, and that has one of its GPIO connected >>>>> to the DUT GPIO. >>>>> >>>>> On the recording app, I use the RTDM device to open, ioctl (enable >>>>> interrupt + timestamp), then select & read the GPIO value. >>>> >>>> When issue happen, the recording app side have got same number of network >>>> data packages and gpio interrupts with that DUT have been toggling? >>>> I am asking this because I met gpio hardware issue that would cause gpio >>>> interrupt missing or invalid gpio interrupts when gpio is connecting on >>>> two different boards. >>>> >>> >>> AFAICT, I'm not missing GPIO edges/interrupts in the app. Regarding >>> network, the DUT and the recoding device are connected to the same switch >>> with the same port config. >>> >>> Moreover, I tried changing the interrupt polarity of the recording device >>> (switched from rising edge to falling edge), and the result is 1-2ms + >>> ~30ms (the width of the pulse of the DUT) + 50ms latency >>> >> >> Can you (or did you already) break down the latencies on the DUT via >> tracing? Is it really the GPIO output path? What is happening in it, >> starting with RT/Linux task switches, mode transitions etc.? >> > > I just did it. > > I did put gpio_pin_interrupt as trigger, then ran my application, triggered > the GPIO. > This is what I get in frozen, but I'm not quite sure how to read it and what > conclusion I could derive : > cat frozen > I-pipe frozen back-tracing service on 4.4.227+/ipipe release #10 > ------------------------------------------------------------ > CPU: 0, Freeze: 218343820846 cycles, Trace Points: 100 (+10) > Calibrated minimum trace-point overhead: 0.461 us > > +----- Hard IRQs ('|': locked) > |+-- Xenomai > ||+- Linux ('*': domain stalled, '+': current, '#': current+stalled) > ||| +---------- Delay flag ('+': > 1 us, '!': > 10 us) > ||| | +- NMI noise ('N') > ||| | | > Type User Val. Time Delay Function (Parent) > : +func -6087+ 1.302 load_balance+0x14 > (run_rebalance_domains+0x7e8) > : +func -6085 0.826 idle_cpu+0x10 (load_balance+0x180) > : +func -6084 0.892 find_busiest_group+0x14 > (load_balance+0x1a4) > : +func -6084 0.757 update_group_capacity+0x14 > (find_busiest_group+0x128) > : +func -6083+ 1.452 __msecs_to_jiffies+0x10 > (update_group_capacity+0x30) > : +func -6081+ 1.535 idle_cpu+0x10 > (find_busiest_group+0x1e4) > : +func -6080+ 1.410 idle_cpu+0x10 > (find_busiest_group+0x1e4) > : +func -6078 0.967 __msecs_to_jiffies+0x10 > (run_rebalance_domains+0x810) > : +func -6077 0.886 __rcu_read_unlock+0x10 > (run_rebalance_domains+0x648) > : +func -6077 0.820 rcu_bh_qs+0x10 (__do_softirq+0x1b0) > : +func -6076 0.742 ipipe_stall_root+0x10 > (__do_softirq+0x1b4) > : +func -6075 0.766 ipipe_root_only+0x10 > (ipipe_stall_root+0x18) > :| +begin 0x80000001 -6074 0.934 ipipe_trace_begin+0x24 > (ipipe_root_only+0xb8) > :| +end 0x80000001 -6073 0.811 ipipe_trace_end+0x24 > (ipipe_root_only+0xfc) > :| +begin 0x80000001 -6072 0.895 ipipe_trace_begin+0x24 > (ipipe_stall_root+0x78) > :| #end 0x80000001 -6072 0.847 ipipe_trace_end+0x24 > (ipipe_stall_root+0xb8) > : #func -6071 0.814 __local_bh_enable+0x10 > (__do_softirq+0x214) > : #func -6070 0.760 ipipe_test_root+0x10 > (__local_bh_enable+0x1c) > :| #begin 0x80000001 -6069 0.907 ipipe_trace_begin+0x24 > (ipipe_test_root+0x74) > :| #end 0x80000001 -6068 0.898 ipipe_trace_end+0x24 > (ipipe_test_root+0xb8) > : #func -6067 0.811 rcu_irq_exit+0x10 (irq_exit+0x84) > : #func -6067 0.781 ipipe_test_and_stall_root+0x10 > (rcu_irq_exit+0x18) > : #func -6066 0.799 ipipe_root_only+0x10 > (ipipe_test_and_stall_root+0x18) > :| #begin 0x80000001 -6065+ 1.041 ipipe_trace_begin+0x24 > (ipipe_root_only+0xb8) > :| #end 0x80000001 -6064 0.769 ipipe_trace_end+0x24 > (ipipe_root_only+0xfc) > :| #begin 0x80000001 -6063 0.895 ipipe_trace_begin+0x24 > (ipipe_test_and_stall_root+0x80) > :| #end 0x80000001 -6062 0.841 ipipe_trace_end+0x24 > (ipipe_test_and_stall_root+0xc4) > : #func -6061+ 1.197 rcu_eqs_enter_common.constprop.21+0x10 > (rcu_irq_exit+0x80) > :| #begin 0x80000000 -6060+ 1.413 ipipe_trace_begin+0x24 > (__ipipe_do_sync_stage+0x2b8) > :| +end 0x00000012 -6059+ 1.044 ipipe_trace_end+0x24 > (__ipipe_grab_irq+0x84) > :| +func -6058 0.988 > __ipipe_check_root_interruptible+0x10 (__irq_svc+0x70) > :| +func -6057 0.976 ipipe_test_root+0x10 > (__ipipe_check_root_interruptible+0x68) > :| +func -6056 0.829 __ipipe_bugon_irqs_enabled+0x10 > (__ipipe_fast_svc_irq_exit+0x4) > :| +end 0x90000000 -6055 0.913 __ipipe_fast_svc_irq_exit+0x20 > (ipipe_unstall_root+0x88) > : +func -6054 0.781 ipipe_test_root+0x10 > (cpu_startup_entry+0x12c) > :| +begin 0x80000001 -6053 0.868 ipipe_trace_begin+0x24 > (ipipe_test_root+0x74) > :| +end 0x80000001 -6052 0.781 ipipe_trace_end+0x24 > (ipipe_test_root+0xb8) > : +func -6052 0.748 rcu_idle_exit+0x10 > (cpu_startup_entry+0x138) > : +func -6051 0.739 ipipe_test_and_stall_root+0x10 > (rcu_idle_exit+0x18) > : +func -6050 0.775 ipipe_root_only+0x10 > (ipipe_test_and_stall_root+0x18) > :| +begin 0x80000001 -6049+ 1.011 ipipe_trace_begin+0x24 > (ipipe_root_only+0xb8) > :| +end 0x80000001 -6048 0.742 ipipe_trace_end+0x24 > (ipipe_root_only+0xfc) > :| +begin 0x80000001 -6048 0.940 ipipe_trace_begin+0x24 > (ipipe_test_and_stall_root+0x80) > :| #end 0x80000001 -6047 0.790 ipipe_trace_end+0x24 > (ipipe_test_and_stall_root+0xc4) > : #func -6046 0.859 > rcu_eqs_exit_common.constprop.19+0x10 (rcu_idle_exit+0x8c) > : #func -6045 0.772 ipipe_unstall_root+0x10 > (rcu_idle_exit+0x78) > :| #begin 0x80000000 -6044 0.814 ipipe_trace_begin+0x24 > (ipipe_unstall_root+0x98) > :| #func -6043+ 1.077 ipipe_root_only+0x10 > (ipipe_unstall_root+0x24) > :| +end 0x80000000 -6042 0.835 ipipe_trace_end+0x24 > (ipipe_unstall_root+0x84) > : +func -6042 0.922 arch_cpu_idle_exit+0x10 > (cpu_startup_entry+0xfc) > : +func -6041 0.793 ipipe_stall_root+0x10 > (cpu_startup_entry+0xc4) > : +func -6040 0.724 ipipe_root_only+0x10 > (ipipe_stall_root+0x18) > :| +begin 0x80000001 -6039+ 1.098 ipipe_trace_begin+0x24 > (ipipe_root_only+0xb8) > :| +end 0x80000001 -6038 0.772 ipipe_trace_end+0x24 > (ipipe_root_only+0xfc) > :| +begin 0x80000001 -6037 0.841 ipipe_trace_begin+0x24 > (ipipe_stall_root+0x78) > :| #end 0x80000001 -6036 0.763 ipipe_trace_end+0x24 > (ipipe_stall_root+0xb8) > : #func -6036 0.838 arch_cpu_idle_enter+0x10 > (cpu_startup_entry+0xc8) > : #func -6035 0.745 arm_heavy_mb+0x10 > (arch_cpu_idle_enter+0x1c) > : #func -6034 0.916 l2c210_sync+0x10 (arm_heavy_mb+0x2c) > : #func -6033+ 1.062 tick_check_broadcast_expired+0x10 > (cpu_startup_entry+0xd8) > : #func -6032 0.787 rcu_idle_enter+0x10 > (cpu_startup_entry+0x124) > : #func -6031 0.745 ipipe_test_and_stall_root+0x10 > (rcu_idle_enter+0x18) > : #func -6031 0.751 ipipe_root_only+0x10 > (ipipe_test_and_stall_root+0x18) > :| #begin 0x80000001 -6030 0.991 ipipe_trace_begin+0x24 > (ipipe_root_only+0xb8) > :| #end 0x80000001 -6029 0.772 ipipe_trace_end+0x24 > (ipipe_root_only+0xfc) > :| #begin 0x80000001 -6028 0.892 ipipe_trace_begin+0x24 > (ipipe_test_and_stall_root+0x80) > :| #end 0x80000001 -6027 0.847 ipipe_trace_end+0x24 > (ipipe_test_and_stall_root+0xc4) > : #func -6026 0.922 > rcu_eqs_enter_common.constprop.21+0x10 (rcu_idle_enter+0x90) > : #func -6025 0.862 default_idle_call+0x10 > (cpu_startup_entry+0x128) > : #func -6024 0.877 arch_cpu_idle+0x10 > (default_idle_call+0x38) > :| #begin 0x80000000 -6024! 5992.167 ipipe_trace_begin+0x24 > (arch_cpu_idle+0xb8)
Here your system (or this core) went idle, waiting for the next event. > :| +func -31 0.760 ipipe_unstall_root+0x10 > (arch_cpu_idle+0x30) Comming back from idle. > :| +func -31+ 1.116 ipipe_root_only+0x10 > (ipipe_unstall_root+0x24) > :| +end 0x80000000 -30 0.931 ipipe_trace_end+0x24 > (ipipe_unstall_root+0x84) > :| +begin 0x90000000 -29 0.844 __irq_svc+0x58 > (ipipe_unstall_root+0x88) > :| +func -28 0.925 gic_handle_irq+0x10 (__irq_svc+0x6c) > :| +func -27 0.904 irq_find_mapping+0x10 > (gic_handle_irq+0x50) > :| +func -26 0.940 __ipipe_grab_irq+0x10 > (gic_handle_irq+0x58) > :| +begin 0x000000c9 -25 0.826 ipipe_trace_begin+0x24 > (__ipipe_grab_irq+0x58) > :| +func -24 0.814 __ipipe_dispatch_irq+0x10 > (__ipipe_grab_irq+0x7c) > :| +func -23+ 1.275 irq_to_desc+0x10 > (__ipipe_dispatch_irq+0x184) > :| +func -22+ 1.679 irq_to_desc+0x10 > (__ipipe_dispatch_irq+0x198) > :| +func -20+ 2.092 ucc_gpio_irqhandler+0x14 > (__ipipe_dispatch_irq+0x1fc) > :| +func -18+ 1.413 irq_find_mapping+0x10 > (ucc_gpio_irqhandler+0x84) > :| +begin 0x000000e3 -17 0.757 ipipe_trace_begin+0x24 > (ucc_gpio_irqhandler+0x8c) > :| +func -16 0.778 __ipipe_dispatch_irq+0x10 > (ucc_gpio_irqhandler+0x98) > :| +func -15+ 1.023 irq_to_desc+0x10 > (__ipipe_dispatch_irq+0x184) > :| +func -14+ 1.494 irq_to_desc+0x10 > (__ipipe_dispatch_irq+0x198) > :| +func -13+ 1.014 __ipipe_ack_level_irq+0x10 > (__ipipe_dispatch_irq+0x1fc) > :| +func -12 0.763 ucc_gpio_irq_mask+0x10 > (__ipipe_ack_level_irq+0x54) > :| +func -11+ 1.248 __ipipe_spin_lock_irqsave+0x10 > (ucc_gpio_irq_mask+0x2c) > :| #func -10+ 1.619 __ipipe_spin_unlock_irqrestore+0x10 > (ucc_gpio_irq_mask+0x4c) > :| +func -8+ 1.239 __ipipe_set_irq_pending+0x10 > (__ipipe_dispatch_irq+0x3bc) > :| +end 0x000000e3 -7 0.994 ipipe_trace_end+0x24 > (ucc_gpio_irqhandler+0xa0) > :| +func -6+ 1.029 gic_eoi_irq+0x10 > (ucc_gpio_irqhandler+0xd4) > :| +func -5+ 1.353 __ipipe_do_sync_pipeline+0x14 > (__ipipe_dispatch_irq+0x17c) > :|+ func -4+ 1.449 __ipipe_do_sync_stage+0x14 > (__ipipe_do_sync_pipeline+0xf0) > :|# func -2+ 1.191 xnintr_irq_handler+0x14 > (__ipipe_do_sync_stage+0x200) > :|# func -1+ 1.455 ___xnlock_get+0x10 > (xnintr_irq_handler+0xc0) > <|# func 0 1.107 gpio_pin_interrupt+0x10 > (xnintr_irq_handler+0xf4) And here we start to process that GPIO interrupt in the RTDM handler, roughly after 30 µs (which are also due to tracing overhead). So far nothing suspiciuos. > |# func 1 1.236 xnclock_core_read_monotonic+0x10 > (gpio_pin_interrupt+0x1c) > |# func 2 1.224 rtdm_event_signal+0x10 > (gpio_pin_interrupt+0x2c) Here some likely waiting RT task is signalled. Does that one notice a too high latency? Jan > |# func 3 1.032 ___xnlock_get+0x10 > (rtdm_event_signal+0x80) > |# func 4 0.997 xnsynch_flush+0x14 > (rtdm_event_signal+0xa0) > |# func 5 1.835 ___xnlock_get+0x10 > (xnsynch_flush+0x74) > |# func 7 1.083 __xnselect_signal+0x10 > (rtdm_event_signal+0x1e4) > |# func 8 0.856 xnsynch_flush+0x14 > (__xnselect_signal+0x90) > |# func 9 0.958 ___xnlock_get+0x10 > (xnsynch_flush+0x74) > |# func 10 0.886 xnthread_resume+0x14 > (xnsynch_flush+0xe8) > |# func 11 0.000 ___xnlock_get+0x10 > (xnthread_resume+0x7c) > > > >> Jan >> >> -- >> Siemens AG, T RDA IOT >> Corporate Competence Center Embedded Linux > -- Siemens AG, T RDA IOT Corporate Competence Center Embedded Linux
