On 2/10/2019 11:04 PM, Mike Galbraith wrote:
On Sat, 2019-02-09 at 15:50 -0800, L A Walsh wrote:
On 2/6/2019 7:34 AM, Richard Brown wrote:
CONFIG_PREEMPT_NONE (as seen in SLE/Leap)
Really? the desktop distro Leap uses a config setting
intended for servers and that is documented to give
unreliable response time for interactive use?
Shrug. Yes, worst case latency is higher than alternative models, but
general case latency is fine, as it must must be, else servers couldn't
use PREEMPT_NONE to service human interfacing clients. PREEMPT_NONE is
just one of three trade-offs, each of the three a mixed bag of strength
For a desktop user who might like to user their computer
interactively and use it to play music or stream a video while
they compile the kernel, which would be the recommended
As for using PREEMPT-NONE to service humans who in my parents
generation used slide rules or an abacus, I'm sure tolerating
delays under PREEMPT-NONE is hardly noticeable. But other people
have a lower tolerance, to the point that anything over 100ms
(full round trip) has people complaining about the slow ping
times for a modern PvP game.
In the same light, there would be a 'best' choice for someone
recording live video needing a minimum of latency, and
for computers run servicing storage or web requests or running
as build machines 24/7, the most efficient kernel would
also be a best choice.
It really isn't based on averages over long periods, but in the
case of real-time recording or needing fast response time having
something set for no preemption isn't the best choice.
That said -- if it is known something is causing worst case
performance under PREEMPT_NONE, it should be fixed besides being
run in a SW environment where it won't or can't
show the bad behavior.
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