* low_latency flag has gone missing
@ 2021-03-02 14:49 Grant Edwards
2021-03-03 7:12 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: Grant Edwards @ 2021-03-02 14:49 UTC (permalink / raw)
To: linux-serial
Some of the serial drivers that I maintain can make a tradeoff between
CPU usage, throughput, and rx data latency. For the past 20 years,
I've based that tradeoff on the tty struct's "low_latency" flag. This
allowed the user to choose between high-throughput with low CPU usage,
or higher CPU usage with lower latency and lower total throughput.
That low_latency flag appears to have "gone away" in v5.12.
How are users now supposed to indicate their desire for low-latency
operation for a serial port?
--
Grant
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: low_latency flag has gone missing
2021-03-02 14:49 low_latency flag has gone missing Grant Edwards
@ 2021-03-03 7:12 ` Greg KH
0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2021-03-03 7:12 UTC (permalink / raw)
To: Grant Edwards; +Cc: linux-serial
On Tue, Mar 02, 2021 at 02:49:31PM -0000, Grant Edwards wrote:
> Some of the serial drivers that I maintain can make a tradeoff between
> CPU usage, throughput, and rx data latency. For the past 20 years,
> I've based that tradeoff on the tty struct's "low_latency" flag. This
> allowed the user to choose between high-throughput with low CPU usage,
> or higher CPU usage with lower latency and lower total throughput.
>
> That low_latency flag appears to have "gone away" in v5.12.
>
> How are users now supposed to indicate their desire for low-latency
> operation for a serial port?
Given that there are no in-kernel users of this "option", perhaps
hardware has caught up to the fact that it really wasn't doing anything
:)
Do you have proof that it was working as expected somehow?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-03-02 14:49 low_latency flag has gone missing Grant Edwards
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