From nobody Thu Mar 23 18:55:22 2023 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4PjF0L4MZ8z41gjx for ; Thu, 23 Mar 2023 18:55:30 +0000 (UTC) (envelope-from george+freebsd@m5p.com) Received: from mailhost.m5p.com (mailhost.m5p.com [74.104.188.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "m5p.com", Issuer "R3" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4PjF0K6qqVz3mmv for ; Thu, 23 Mar 2023 18:55:29 +0000 (UTC) (envelope-from george+freebsd@m5p.com) Authentication-Results: mx1.freebsd.org; dkim=none; spf=pass (mx1.freebsd.org: domain of george+freebsd@m5p.com designates 74.104.188.4 as permitted sender) smtp.mailfrom=george+freebsd@m5p.com; dmarc=none Received: from [IPV6:2001:470:1f07:15ff::26] (court.m5p.com [IPv6:2001:470:1f07:15ff:0:0:0:26]) (authenticated bits=0) by mailhost.m5p.com (8.16.1/8.15.2) with ESMTPSA id 32NItMdK009403 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO) for ; Thu, 23 Mar 2023 14:55:28 -0400 (EDT) (envelope-from george+freebsd@m5p.com) Message-ID: <4831cdf2-57d7-a699-4ece-7f1f07b05845@m5p.com> Date: Thu, 23 Mar 2023 14:55:22 -0400 List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: Periodic rant about SCHED_ULE To: freebsd-hackers@freebsd.org References: <202303221710.32MHAhe9047582@gndrsh.dnsmgr.net> <27f46bc2-54f8-f5aa-79ca-184e86d185d8@m5p.com> Content-Language: en-US From: George Mitchell In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=0.0 required=10.0 tests=HELO_NO_DOMAIN,NICE_REPLY_A autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on mattapan.m5p.com X-Spamd-Result: default: False [-3.22 / 15.00]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_LONG(-0.99)[-0.987]; NEURAL_HAM_SHORT(-0.93)[-0.929]; R_SPF_ALLOW(-0.20)[+a]; MIME_GOOD(-0.10)[text/plain]; R_DKIM_NA(0.00)[]; TAGGED_FROM(0.00)[freebsd]; MLMMJ_DEST(0.00)[freebsd-hackers@freebsd.org]; FROM_EQ_ENVFROM(0.00)[]; ASN(0.00)[asn:701, ipnet:74.104.0.0/16, country:US]; MIME_TRACE(0.00)[0:+]; DMARC_NA(0.00)[m5p.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; RCVD_COUNT_TWO(0.00)[2] X-Rspamd-Queue-Id: 4PjF0K6qqVz3mmv X-Spamd-Bar: --- X-ThisMailContainsUnwantedMimeParts: N 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