Date: Thu, 23 Mar 2023 14:55:22 -0400 From: George Mitchell <george+freebsd@m5p.com> To: freebsd-hackers@freebsd.org Subject: Re: Periodic rant about SCHED_ULE Message-ID: <4831cdf2-57d7-a699-4ece-7f1f07b05845@m5p.com> In-Reply-To: <ec4212aa-6afa-d294-1a2a-5d84c4c2398e@FreeBSD.org> References: <202303221710.32MHAhe9047582@gndrsh.dnsmgr.net> <27f46bc2-54f8-f5aa-79ca-184e86d185d8@m5p.com> <b29444be-1146-185b-d4cc-d422f9bcdd8c@denninger.net> <a4d511bc-5d1a-4859-0dcb-d24a2185ef20@m5p.com> <ec4212aa-6afa-d294-1a2a-5d84c4c2398e@FreeBSD.org>
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On 3/23/23 06:03, David Chisnall wrote: > On 22/03/2023 18:03, George Mitchell wrote: >> Rebuilding the kernel is the only way I know. In an ideal world, the >> scheduler would be a loadable kernel module (if that's even possible), > > Solaris supports multiple schedulers, as I believe does Linux, but I > think in both cases it's a boot-time option. It's been too long since I > looked at the early boot order to know if there's anything that handles > linking the loader-provided modules that depends on any scheduler data > structures. Doing that audit and ensuring that there aren't would be > the first step. From there, it should be mostly build-system > infrastructure to allow building the two schedulers as modules and > switching between them at boot. > > Allowing switching schedulers after boot time is a much harder problem. > I know some microkernels have done it, but even there (where the > scheduler is a separate service) it's far from easy. > > David I never expected to be able to switch schedulers after boot time, but I assume even switching at boot time would require the scheduler to be a kernel loadable module. -- George
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