Re: [External] : Re: data throttling under load when serial to usb adapter is used

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Dec 20, 2021 at 11:19:03AM +0100, Filip Žaludek wrote:
> 
> > 
> > Using 'cat' is not a good way to ever use a serial port.  Please use a
> > tool that can properly detect and use the serial port flow control
> > settings, which should prevent the issues you are seeing here.
> > 
> > Is socat using flow control?  If so, which settings, hardware or
> > software flow control?
> > 
> > Also please note that the usb-serial devices you are using here are
> > _very_ cheap and not good for huge amounts of data like you seem to want
> > to use here.  I would recommend a much more robust usb-serial device if
> > you need high data rates and good hardware flow control handling.  Most
> > of the time, the devices you have here do not even have any hardware
> > flow control support as the manufacturers do not hook up those lines.
> > So be careful.
> > 
> > thanks,
> > 
> > greg k-h
> > 
> 
> 
> 
>  Yes, you are right! Such gadget hardware is without hw flow control. I am using
> serial line only to capture console logs. I've tested both commands also with
> sw flow control ixon, ixoff with similar results.
> 
>  Hopefully somebody sitting on scarce big iron with both usb port and serial port
> with proper hw flow control from this list gets attracted to kindly re-test.
> 
> Interesting part for me is that only serial to usb direction is failing..

Makes sense, these devices are not designed for lots of high-speed data
being sent to them.  Please use a device that is designed for that if
you wish to do this.

thanks,

greg k-h