printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

poplitard — Tue, 22 Aug 2023 14:24:11 GMT

Hey, so the first screenshot shows a batch of prints at 50s followed by a second batch of prints at 51s. The second screenshot shows printks without buffering.

I think I figured it out, it seems like in ncs 2.2.0 i didnt have to explicitly use CONFIG_LOG_PRINTK=n because it was disabled by default

the newer version of zephyr in ncs 2.4.0 has CONFIG_LOG_PRINTK enabled by default, so you have to disable it to prevent printk buffering

printk and logs share the same output backend according to the documentation, which means that printks will be buffered before they outputting anything

https://docs.zephyrproject.org/latest/services/logging/index.html#printk

the config files in the lesson needs to include CONFIG_LOG_PRINTK= to reflect this change (to print instantly)

im a relatively new dev, and i havent really contributed to opensource projects yet, let me know if I can open a pr for this and contribute, thanks!

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

Menon — Tue, 22 Aug 2023 13:55:11 GMT

Hello Richard,

I was answering to the other person(poplitard) who pasted a screenshot with time stamps. Yes, I tried devacademy sample and I can see the delay that you mentioned (not exactly sure how much). I am still on this case and will try to find the cause of delay happening.

Kind Regards,

Abhijith

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

Richard11115 — Tue, 22 Aug 2023 13:36:19 GMT

Are you using a nrf52840 with the modified Lesson 5 Exercise 1 Solution repo code from the course NRF Connect Fundamentals? Millisecond delays would be fine but these are second delays so are causing serious issues

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

Menon — Tue, 22 Aug 2023 13:15:40 GMT

Hello,

While checking the time stamps I can see some milliseconds delay but isn't that usual? I can't find a delay greater than or equal to 1 second like you pointed out. Please excuse if I missed something.

Kind Regards,

Abhijith

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

poplitard — Mon, 21 Aug 2023 14:58:41 GMT

Im running the following piece of code:

#include <zephyr/kernel.h>

int main(void)
{
 while(1)
 {
 printk("Hello World\n");
 k_sleep(K_MSEC(100));
 }
 return 0;
}

with the following configs:

CONFIG_LOG=y
CONFIG_PRINTK=y
CONFIG_SERIAL=y

and what i see is that is takes about a second before it actually sends anything over uart:

if i include this (or disable logs entirely):

CONFIG_LOG_PRINTK=n

it runs consistently:

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

Richard11115 — Mon, 21 Aug 2023 14:18:18 GMT

Yes, I tested it just roughly with a timer it averages around 1.5 seconds when CONFIG_LOG is enabled while it's virtually instant when CONFIG_LOG is disabled

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

Menon — Mon, 21 Aug 2023 14:14:47 GMT

Hello,

Yes, I can see a very slight delay in printing while enabling the log module. For me, it is very slight; I probably can't say it is 2 seconds because I haven't checked how much difference in time it creates with CONFIG_LOG enabled. But have you tested this and found that it is taking 2 seconds?

Kind Regards,

Abhijith

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

poplitard — Mon, 21 Aug 2023 13:21:01 GMT

Having the same problem over here, except im usnig the uart backend for logs

Enabling config_log holds back some printks and seems to print only when a certain amount of data has accumulated in the buffer

When I print frequently i have a lot of messages that get dropped as a result

RE: printk becomes slow when CONFIG_LOG=y and trying to recieve serial communication over uart

Menon — Fri, 18 Aug 2023 11:43:14 GMT

Hello,

I am letting you know that I have been assigned to this case, and I will try to test this here.

I will get back to you after testing this.

Kind Regards,

Abhijith