Thanks Johan, you save my day. Indeed, soft irq coming from ftdi_sio updates, with very high rate. (dyndbg='file drivers/usb/* +p') reducing latency timer = reducing sofirq. Problem solved. Antoine Aubert a.aubert@xxxxxxxxxxx Le 16/01/2017 à 15:47, Johan Hovold a écrit : > [ +CC: linux-usb ] > > On Mon, Jan 16, 2017 at 12:14:03PM +0100, Boris Brezillon wrote: >> On Mon, 16 Jan 2017 11:54:23 +0100 >> Antoine Aubert <a.aubert@xxxxxxxxxxx> wrote: >> >>> Also, I made a big misunderstanding >>> >>> With EHCI + OHCI = high level of softirq (USB2.0) >> Well, the number of irqs and softirqs are likely to be related (you >> usually trigger a softirq after you received an hardirq). >> >>> OHCI only = normal level >> What about EHCI only? And what happens if you only plug 1 device? >> Please share the content of /proc/interrupts (and everything you think >> is relevant) for each of these cases. >> >>> Le 16/01/2017 à 11:31, Antoine Aubert a écrit : >>>> Thx for your answer Boris >>>> >>>> Le 16/01/2017 à 10:02, Boris Brezillon a écrit : >>>>> Hi Antoine, >>>>> >>>>> On Mon, 16 Jan 2017 08:45:58 +0100 >>>>> Antoine Aubert <a.aubert@xxxxxxxxxxx> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> Im working on a AT91SAM9G25cu board >>>>>> (arch/arm/boot/dts/at91-kizboxmini.dts). We use linux-4.1.31, and when >>>>>> OHCI is enabled, I got some wired effects. >>>>> Can you test on a more recent kernel (4.9 or 4.10-rc4)? >>>> I'll give a try, just need little time ;) >>>>>> eg with 3 FTDI pluged, interrupts: more than 3.5k/s, cpu softirq > 24%, >>>>>> loadavg > 0.5 >>>>> Can you check which interrupt is triggered (cat /proc/interrupts), >>>> cat /proc/interrupts >>>> CPU0 >>>> 16: 2286 atmel-aic 1 Level pmc, at91_tick, at91_rtc, ttyS0 >>>> 17: 0 PMC 17 Level main_rc_osc >>>> 18: 0 PMC 0 Level main_osc >>>> 19: 0 PMC 16 Level mainck >>>> 20: 0 PMC 1 Level clk-plla >>>> 21: 0 PMC 6 Level clk-utmi >>>> 22: 0 PMC 3 Level clk-master >>>> 23: 945527 atmel-aic 17 Level tc_clkevt >>>> 24: 21815 atmel-aic 20 Level at_hdmac >>>> 25: 0 atmel-aic 21 Level at_hdmac >>>> 30: 120299 atmel-aic 24 Level eth0 >>>> 31: 22783651 atmel-aic 22 Level ehci_hcd:usb1, ohci_hcd:usb2 >>>> 99: 0 GPIO 16 Edge PB_RST >>>> 100: 0 GPIO 17 Edge PB_PROG >>>> Err: 0 > Note that the ftdi driver uses a low-latency setting by default which > implies that the device sends a status update every millisecond. Hence, > the 1k interrupts per second (per device) while the port is open is > expected. > > You can disable the low-latency behaviour using setserial: > > setserial /dev/ttyUSB0 ^low_latency > > and see the number of interrupts drop to 1/16th. This can then be > reduced further by changing the latency_timer from its > (non-low-latency) default of 16 ms, for example: > > echo 64 >/sys/bus/usb-serial/devices/ttyUSB0/latency_timer > > Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
