Re: [PATCH v2] kbuild: use -flive-patching when CONFIG_LIVEPATCH is enabled

[Josh Poimboeuf <jpoimboe@redhat.com>]

On Thu, Apr 04, 2019 at 08:44:11PM +0200, Miroslav Benes wrote:
> GCC 9 introduces a new option, -flive-patching. It disables certain
> optimizations which could make a compilation unsafe for later live
> patching of the running kernel.
> 
> The option is used only if CONFIG_LIVEPATCH is enabled and $(CC)
> supports it.
> 
> Performance impact of the option was measured on three different
> Intel machines - two bigger NUMA boxes and one smaller UMA box. Kernel
> intensive (IO, scheduling, networking) benchmarks were selected, plus a
> set of HPC workloads from NAS Parallel Benchmark. The tests were done on
> upstream kernel 5.0-rc8 with openSUSE Leap 15.0 userspace.
> 
> The majority of the tests is unaffected. The only significant exception
> is the scheduler section which suffers 1-3% degradation.
> 
> Evaluated-by: Giovanni Gherdovich <ggherdovich@suse.cz>
> Signed-off-by: Miroslav Benes <mbenes@suse.cz>
> ---
> The patch is based on master branch of the livepatching tree on
> git.kernel.org.
> 
> Many thanks to Giovanni who ran the whole testing campaign and analyzed
> the results. I archived the dashboard and detailed data. If anyone is
> interested, we could probably set up a public website somewhere.

Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>

While we're on the subject, I'm glad to see ongoing activity on
klp-convert (though I haven't had a chance to follow the discussions).
What's the status of the rest of the needed bits?

- kgraft-analysis-tool - will this also be submitted for inclusion in
  the kernel tree?

- Documentation about how to create a patch

- The other bits I think Nicolai has been working on to eliminate all
  the manual steps

-- 
Josh