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Date:   Thu, 10 Jan 2019 17:30:30 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Oleksij Rempel <o.rempel@pengutronix.de>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Jiri Slaby <jslaby@suse.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 3/3] drivers/tty: increase priority for
 tty_buffer_worker
Message-ID: <20190110163030.GB19693@kroah.com>
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On Thu, Jan 10, 2019 at 04:19:53PM +0100, Oleksij Rempel wrote:
> > My gut feel is that if somebody still cares deeply about serial line
> > latency, they should look at trying to see if they can do some of the
> > work directly without the bounce to the workqueue. We use workqueues
> > for a reason, but it's possible that some of it could be avoided at
> > least in special cases... And yours sounds like a special case.
> 
> It is for industrial low latency RS-422 based application. The loopback
> test is just easy way to test/reproduce it without additional hardware.
> 
> What is good, mainlineable way to implement it? 

What is the real problem your systems are having?  Are they serial-port
limited?  Is latency a big issue?  Trying to tune for a fake workload
isn't the best way to solve anything :)

thanks,
greg k-h