From: Fabio Estevam <festevam@gmail.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: linux-can@vger.kernel.org,
Oliver Hartkopp <socketcan@hartkopp.net>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: Testing two MCP2518FD's on i.MX8MM
Date: Mon, 21 Jun 2021 09:24:31 -0300 [thread overview]
Message-ID: <CAOMZO5AMP537Qz1MAb-D_27C=WH-5Cf602hichxty95A6db9-A@mail.gmail.com> (raw)
In-Reply-To: <20210615071557.o7fjkleuk777otvm@pengutronix.de>
Hi Marc,
On Tue, Jun 15, 2021 at 4:15 AM Marc Kleine-Budde <mkl@pengutronix.de> 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
next prev parent reply other threads:[~2021-06-21 12:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAOMZO5CwS-cO3W148YHVYFwcL3QC8oFJfeQBb+WN=QgEPU7AsQ@mail.gmail.com>
2021-06-12 15:10 ` Testing two MCP2518FD's on i.MX8MM Fabio Estevam
2021-06-15 7:15 ` Marc Kleine-Budde
2021-06-21 12:24 ` Fabio Estevam [this message]
2021-06-21 12:37 ` Marc Kleine-Budde
2021-06-21 13:07 ` Fabio Estevam
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