On Wed, 2019-02-06 at 16:34 +0100, Richard Brown wrote:
Hi all,
I was talking to Takashi lately about the saga that is bug 1112824
http://bugzilla.opensuse.org/show_bug.cgi?id=1112824
In that bug a kernel with CONFIG_PREEMPT_VOLUNTARY=y was provided, and a user reported that it did not improve the situation for them
However, as a heavy GNOME user, in my own testing, I have found the following results
CONFIG_PREEMPT_NONE (as seen in SLE/Leap) 'feels' slower, but is usable without the sort of stalls/hangs/inputs being dropped that are described in 1112824
CONFIG_PREEMPT (as in Tumbleweed right now) 'feels' faster than _NONE, mostly, but then interactive processes like many functions in GNOME randomly stall/hang with keyboard entries being dropped, as described in 1112824. IOW - I can reproduce the issues reported to a perceptible degree
CONFIG_PREEMPT_VOLUNTARY (as used in 'other distros) 'feels' just as fast as _PREEMPT, without the stalls in GNOME
Hm, what distros use PREEMPT_VOLUNTARY? While PREEMPT_VOLUNTARY is my personal preference as a compromise between throughput and latency (PREEMPT injures throughput way too much for my taste), I have for years been under the impression that most if not all distros were shipping PREEMPT kernels.
I can understand the reluctance to change a kernel config option just because of a bug, and I do understand the argument than this bug could/should be fixed by GNOME doing less stupid stuff in userspace.
That said, I also think it's important that we should aim for defaults somewhat defensively - if _PREEMPT can cause such disruption due to badly written userspace behaviour, but _VOLUNTARY does not, then I think VOLUNTARY is a better option.
Scanning through the BNC, I don't see any reason to consider changing the long used preemption model. It looks to me like something simply went broke recently (as things occasionally do), and that something needs to be hunted down and fixed up. -Mike -- To unsubscribe, e-mail: opensuse-kernel+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-kernel+owner@opensuse.org