Hi Marc, On Tue, Jun 15, 2021 at 4:15 AM Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > The imx SPI driver has quite some overhead, when it comes to small SPI > transfers. The mcp251fd driver performs much better with the SPI IP > cores on the raspi, which have quite good optimized drivers. > > Hook up a scope to the SPI's clock and chip select lines of the imx, > you'll see the time between end of transfer until the chip select is > inactive is longer than the SPI transfer itself. > > I expect most bang for the buck can be archived by adding an IRQ less > busy polling transfer mode, which kicks in below a certain SPI transfer > length. > > On the mcp251xfd driver side, there is some room for optimization. The > basic idea is to reduce the number of SPI transfers by combining several > reads into one transfer. This can be done in some places. > > For peak loads in CAN-2.0 mode it would be interesting to make use of > the remaining RAM for a 2nd FIFO. Thanks for your reply. I do see some RCU related errors every time the application is launched: # ./cantest.sh start root@verdin-imx8mm:~# interface = can1, family = 29, ty[ 17.484220] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! [ 17.484240] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! pe = 3, proto = 1 interface = ca[ 17.502870] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! n0, family = 29, type = 3, proto [ 17.502912] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! = 1 interface = can1, family = 2[ 17.524457] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! 9, type = 3, proto = 1 interface[ 17.524476] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! = can0, family = 29, type = 3, p[ 17.535223] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! roto = 1 [ 17.557284] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! [ 17.557284] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! [ 17.574035] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! [ 17.574037] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! [ 18.435652] sched: RT throttling activated After some time: [ 292.197058] rcu: 0-....: (1 GPs behind) idle=6db/1/0x4000000000000002 softirq=2974/2975 fqs=7882 [ 292.206039] (t=21003 jiffies g=1249 q=1317) [ 292.210316] Task dump for CPU 0: [ 292.213549] task:cansequence state:R running task stack: 0 pid: 374 ppid: 1 flags:0x00000202 [ 292.223485] Call trace: [ 292.225932] dump_backtrace+0x0/0x1a8 [ 292.229613] show_stack+0x18/0x28 [ 292.232936] sched_show_task+0x150/0x170 [ 292.236869] dump_cpu_task+0x44/0x54 [ 292.240453] rcu_dump_cpu_stacks+0xf4/0x13c [ 292.244648] rcu_sched_clock_irq+0x844/0xdc0 [ 292.248929] update_process_times+0x98/0xe8 [ 292.253125] tick_nohz_handler+0xac/0x110 [ 292.257142] arch_timer_handler_phys+0x34/0x48 [ 292.261598] handle_percpu_devid_irq+0x84/0x148 [ 292.266138] handle_domain_irq+0x60/0x90 [ 292.270071] gic_handle_irq+0x54/0x120 [ 292.273833] call_on_irq_stack+0x28/0x50 [ 292.277767] do_interrupt_handler+0x54/0x60 [ 292.281964] el1_interrupt+0x30/0x78 [ 292.285550] el1h_64_irq_handler+0x18/0x28 [ 292.289653] el1h_64_irq+0x78/0x7c [ 292.293061] __audit_syscall_exit+0x8/0x238 [ 292.297256] el0_svc_common+0x60/0xd8 [ 292.300927] do_el0_svc+0x28/0x90 [ 292.304249] el0_svc+0x24/0x38 [ 292.307312] el0t_64_sync_handler+0xb0/0xb8 [ 292.311502] el0t_64_sync+0x198/0x19c 2020-02-12 19:28:40:388 sequence CNT: 1586297, RX: 93 expected: 121 missing: 228 skt overfl d: 0 a: 0 delta: 228 incident: 1 seq_wrap RX: 6196 sequ_wrap_expected: 6196 overall lost: 4294967268 2020-02-12 19:28:40:389 sequence CNT: 95, RX: 121 expected: 95 missing: 26 skt overfl d: 0 a: 0 delta: 26 incident: 2 seq_wrap RX: 6196 sequ_wrap_expected: 6196 overall lost: 4294967294 2020-02-12 19:28:40:389 sequence CNT: 125, RX: 127 expected: 125 missing: 2 skt overfl d: 0 a: 0 delta: 2 incident: 3 seq_wrap RX: 6196 sequ_wrap_expected: 6196 overall lost: 0 Any ideas how these RCU errors could be fixed? Thanks, Fabio Estevam
