From nobody Tue Mar 21 22:52:16 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 4Ph6Lp2Ty2z40x53 for ; Tue, 21 Mar 2023 22:52:34 +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 4Ph6Ln2RYYz4HDR for ; Tue, 21 Mar 2023 22:52:33 +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 32LMqG2A096172 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO) for ; Tue, 21 Mar 2023 18:52:21 -0400 (EDT) (envelope-from george+freebsd@m5p.com) Message-ID: Date: Tue, 21 Mar 2023 18:52:16 -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 Content-Language: en-US To: FreeBSD Hackers From: George Mitchell Subject: Periodic rant about SCHED_ULE Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=0.0 required=10.0 tests=HELO_NO_DOMAIN 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 [-3.16 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.86)[-0.857]; R_SPF_ALLOW(-0.20)[+a]; MIME_GOOD(-0.10)[text/plain]; FROM_EQ_ENVFROM(0.00)[]; ASN(0.00)[asn:701, ipnet:74.104.0.0/16, country:US]; MIME_TRACE(0.00)[0:+]; MLMMJ_DEST(0.00)[freebsd-hackers@FreeBSD.org]; TO_DN_ALL(0.00)[]; R_DKIM_NA(0.00)[]; DMARC_NA(0.00)[m5p.com]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_HAS_DN(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; TO_MATCH_ENVRCPT_ALL(0.00)[]; ARC_NA(0.00)[]; TAGGED_FROM(0.00)[freebsd] X-Rspamd-Queue-Id: 4Ph6Ln2RYYz4HDR X-Spamd-Bar: --- X-ThisMailContainsUnwantedMimeParts: N Yes, you've all heard it before, but I've just reverified on FreeBSD 13.1-RELEASE-p7 that SCHED_ULE gives terrible performance for "make buildworld" in the presence of a totally compute-bound job (misc/dnetc from ports) running at nice 20. World builds in: 15597 seconds with SCHED_4BSD without dnetc 20477 seconds with SCHED_4BSD with dnetc 16006 seconds with SCHED_ULE without dnetc 50290 seconds with SCHED_ULE with dnetc. When I ask why SCHED_ULE is the default scheduler, I have been told more than once that there is some circumstance in which it gives superior performance. But no one seems to know what circumstance that is. Guess what! I propose that SCHED_4BSD be the default scheduler. -- George