From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 684E7C4742C for ; Fri, 13 Nov 2020 12:15:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 159EF22249 for ; Fri, 13 Nov 2020 12:15:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726963AbgKMMPs (ORCPT ); Fri, 13 Nov 2020 07:15:48 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:7191 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726867AbgKMMPj (ORCPT ); Fri, 13 Nov 2020 07:15:39 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4CXcMH2JbLz15TF6; Fri, 13 Nov 2020 19:54:19 +0800 (CST) Received: from SWX921481.china.huawei.com (10.126.202.143) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.487.0; Fri, 13 Nov 2020 19:54:21 +0800 From: Barry Song To: , , CC: , Barry Song , "Ingo Molnar" , Peter Zijlstra , Mel Gorman , Adrian Freund , Valentin Schneider Subject: [PATCH v3] Documentation: scheduler: fix information on arch SD flags, sched_domain and sched_debug Date: Sat, 14 Nov 2020 00:50:18 +1300 Message-ID: <20201113115018.1628-1-song.bao.hua@hisilicon.com> X-Mailer: git-send-email 2.21.0.windows.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.126.202.143] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This document seems to be out of date for many, many years. Even it has misspelled from the first day. ARCH_HASH_SCHED_TUNE should be ARCH_HAS_SCHED_TUNE ARCH_HASH_SCHED_DOMAIN should be ARCH_HAS_SCHED_DOMAIN Since v2.6.14, kernel completely deleted the relevant code and even arch_init_sched_domains() was deleted. Right now, kernel is asking architectures to call set_sched_topology() to override the default sched domains. On the other hand, to print the schedule debug information, users need to set sched_debug cmdline or enable it by sysfs entry. So this patch also adds the description for sched_debug. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Mel Gorman Cc: Adrian Freund Reviewed-by: Valentin Schneider Signed-off-by: Barry Song --- -v3: * add Reviewed-by of Valentin Schneider * add description of sched_debug Documentation/scheduler/sched-domains.rst | 26 ++++++++++------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git a/Documentation/scheduler/sched-domains.rst b/Documentation/scheduler/sched-domains.rst index 5c4b7f4f0062..8582fa5e9170 100644 --- a/Documentation/scheduler/sched-domains.rst +++ b/Documentation/scheduler/sched-domains.rst @@ -65,21 +65,17 @@ of the SMP domain will span the entire machine, with each group having the cpumask of a node. Or, you could do multi-level NUMA or Opteron, for example, might have just one domain covering its one NUMA level. -The implementor should read comments in include/linux/sched.h: -struct sched_domain fields, SD_FLAG_*, SD_*_INIT to get an idea of -the specifics and what to tune. +The implementor should read comments in include/linux/sched/sd_flags.h: +SD_* to get an idea of the specifics and what to tune for the SD flags +of a sched_domain. -Architectures may retain the regular override the default SD_*_INIT flags -while using the generic domain builder in kernel/sched/core.c if they wish to -retain the traditional SMT->SMP->NUMA topology (or some subset of that). This -can be done by #define'ing ARCH_HASH_SCHED_TUNE. - -Alternatively, the architecture may completely override the generic domain -builder by #define'ing ARCH_HASH_SCHED_DOMAIN, and exporting your -arch_init_sched_domains function. This function will attach domains to all -CPUs using cpu_attach_domain. +Architectures may override the generic domain builder and the default SD flags +for a given topology level by creating a sched_domain_topology_level array and +calling set_sched_topology() with this array as the parameter. The sched-domains debugging infrastructure can be enabled by enabling -CONFIG_SCHED_DEBUG. This enables an error checking parse of the sched domains -which should catch most possible errors (described above). It also prints out -the domain structure in a visual format. +CONFIG_SCHED_DEBUG and adding 'sched_debug' to your cmdline. If you forgot to +tweak your cmdline, you can also flip the /sys/kernel/debug/sched_debug +knob. This enables an error checking parse of the sched domains which should +catch most possible errors (described above). It also prints out the domain +structure in a visual format. -- 2.25.1