Re: CONFIG_PREEMPT_DYNAMIC=y?
On Tue, Oct 10, 2023 at 12:32:22PM +0200, Emanuele Rocca wrote:
> On 2023-10-10 12:14, Johannes Schauer Marin Rodrigues wrote:
> > Quoting Emanuele Rocca (2023-10-10 12:10:07)
> > > Setting CONFIG_HAVE_PREEMPT_DYNAMIC=y on arm64 is likely safe for us too, but
> > > we may want to run some benchmark first to see if there are any noticeable
> > > slowdowns.
> >
> > I have a couple of arm64 boards here that I can run benchmarks on. What would
> > you recommend to run to test the effect of CONFIG_HAVE_PREEMPT_DYNAMIC=y?
>
> I'm not sure what the best benchmark would be, but maybe you could start
> with something generic like timing a kernel build with and without
> PREEMPT_DYNAMIC and throwing 'hey' at your favorite web server?
> https://github.com/rakyll/hey
Whatever you do, check whether having a serial console still works with
that setting. I had trouble with that in kernel 6.5, had some fruitless
discussions on the LKML and developer interest abruptly died when I
found out that the bug I encountered could be worked around by having
those settings:
[1/4998]mh@fan:~ $ grep PREEMPT /boot/config-6.5.6-zgws1
CONFIG_PREEMPT_BUILD=y
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set
CONFIG_PREEMPT_COUNT=y
CONFIG_PREEMPTION=y
CONFIG_PREEMPT_DYNAMIC=y
CONFIG_PREEMPT_RCU=y
CONFIG_HAVE_PREEMPT_DYNAMIC=y
CONFIG_HAVE_PREEMPT_DYNAMIC_CALL=y
CONFIG_PREEMPT_NOTIFIERS=y
CONFIG_DRM_I915_PREEMPT_TIMEOUT=640
CONFIG_DRM_I915_PREEMPT_TIMEOUT_COMPUTE=7500
# CONFIG_DEBUG_PREEMPT is not set
# CONFIG_PREEMPT_TRACER is not set
# CONFIG_PREEMPTIRQ_DELAY_TEST is not set
Greetings
Marc
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