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=-13.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 0B403C433DF for ; Mon, 22 Jun 2020 12:17:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8FF7206FA for ; Mon, 22 Jun 2020 12:17:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728132AbgFVMRw (ORCPT ); Mon, 22 Jun 2020 08:17:52 -0400 Received: from foss.arm.com ([217.140.110.172]:49294 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728103AbgFVMRw (ORCPT ); Mon, 22 Jun 2020 08:17:52 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1C5A91F1; Mon, 22 Jun 2020 05:17:51 -0700 (PDT) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.195.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 02FD73F71E; Mon, 22 Jun 2020 05:17:49 -0700 (PDT) Date: Mon, 22 Jun 2020 13:17:47 +0100 From: Qais Yousef To: Phil Auld Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Vincent Guittot , Steven Rostedt , Juri Lelli , Mel Gorman Subject: Re: [PATCH] Sched: Add a tracepoint to track rq->nr_running Message-ID: <20200622121746.b43ziyjq2eqsseym@e107158-lin.cambridge.arm.com> References: <20200619141120.1476-1-pauld@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200619141120.1476-1-pauld@redhat.com> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/19/20 10:11, Phil Auld wrote: > Add a bare tracepoint trace_sched_update_nr_running_tp which tracks > ->nr_running CPU's rq. This is used to accurately trace this data and > provide a visualization of scheduler imbalances in, for example, the > form of a heat map. The tracepoint is accessed by loading an external > kernel module. An example module (forked from Qais' module and including > the pelt related tracepoints) can be found at: > > https://github.com/auldp/tracepoints-helpers.git > > A script to turn the trace-cmd report output into a heatmap plot can be > found at: > > https://github.com/jirvoz/plot-nr-running > > The tracepoints are added to add_nr_running() and sub_nr_running() which > are in kernel/sched/sched.h. Since sched.h includes trace/events/tlb.h > via mmu_context.h we had to limit when CREATE_TRACE_POINTS is defined. > > Signed-off-by: Phil Auld > CC: Qais Yousef > CC: Ingo Molnar > CC: Peter Zijlstra > CC: Vincent Guittot > CC: linux-kernel@vger.kernel.org > --- > include/trace/events/sched.h | 4 ++++ > kernel/sched/core.c | 9 ++++----- > kernel/sched/fair.c | 2 -- > kernel/sched/pelt.c | 2 -- > kernel/sched/sched.h | 12 ++++++++++++ > 5 files changed, 20 insertions(+), 9 deletions(-) > > diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h > index ed168b0e2c53..a6d9fe5a68cf 100644 > --- a/include/trace/events/sched.h > +++ b/include/trace/events/sched.h > @@ -634,6 +634,10 @@ DECLARE_TRACE(sched_overutilized_tp, > TP_PROTO(struct root_domain *rd, bool overutilized), > TP_ARGS(rd, overutilized)); > > +DECLARE_TRACE(sched_update_nr_running_tp, > + TP_PROTO(int cpu, int change, unsigned int nr_running), > + TP_ARGS(cpu, change, nr_running)); > + > #endif /* _TRACE_SCHED_H */ > > /* This part must be outside protection */ > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 9a2fbf98fd6f..6f28fdff1d48 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6,7 +6,10 @@ > * > * Copyright (C) 1991-2002 Linus Torvalds > */ > + > +#define SCHED_CREATE_TRACE_POINTS > #include "sched.h" > +#undef SCHED_CREATE_TRACE_POINTS > > #include > > @@ -21,9 +24,6 @@ > > #include "pelt.h" > > -#define CREATE_TRACE_POINTS > -#include > - > /* > * Export tracepoints that act as a bare tracehook (ie: have no trace event > * associated with them) to allow external modules to probe them. > @@ -34,6 +34,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp); > EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp); > EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp); > EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp); > +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp); > > DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); > > @@ -7969,5 +7970,3 @@ const u32 sched_prio_to_wmult[40] = { > /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717, > /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, > }; > - > -#undef CREATE_TRACE_POINTS > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index da3e5b54715b..fe5d9b6db8f7 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -22,8 +22,6 @@ > */ > #include "sched.h" > > -#include > - > /* > * Targeted preemption latency for CPU-bound tasks: > * > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > index b647d04d9c8b..bb69a0ae8d6c 100644 > --- a/kernel/sched/pelt.c > +++ b/kernel/sched/pelt.c > @@ -28,8 +28,6 @@ > #include "sched.h" > #include "pelt.h" > > -#include > - > /* > * Approximate: > * val * y^n, where y^32 ~= 0.5 (~1 scheduling period) > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index db3a57675ccf..6ae96679c169 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -75,6 +75,15 @@ > #include "cpupri.h" > #include "cpudeadline.h" > > +#ifdef SCHED_CREATE_TRACE_POINTS > +#define CREATE_TRACE_POINTS > +#endif > +#include > + > +#ifdef SCHED_CREATE_TRACE_POINTS > +#undef CREATE_TRACE_POINTS > +#endif > + > #ifdef CONFIG_SCHED_DEBUG > # define SCHED_WARN_ON(x) WARN_ONCE(x, #x) > #else > @@ -1959,6 +1968,7 @@ static inline void add_nr_running(struct rq *rq, unsigned count) > unsigned prev_nr = rq->nr_running; > > rq->nr_running = prev_nr + count; > + trace_sched_update_nr_running_tp(cpu_of(rq), count, rq->nr_running); This is a very specific call site, so I guess it looks fine to pass very specific info too. But I think we can do better by just passing struct rq and add a new helper sched_trace_rq_nr_running() (see the bottom of fair.c for a similar helper functions for tracepoints). This will allow the user to extract, cpu, nr_running and potentially other info while only pass a single argument to the tracepoint. Potentially extending its future usefulness. The count can be inferred by storing the last nr_running and taking the diff when a new call happens. ... cpu = sched_trace_rq_cpu(rq); nr_running = sched_trace_rq_nr_running(rq); count = last_nr_running[cpu] - nr_running; last_nr_running[cpu] = nr_running; ... I haven't looked at BTF, but it could potentially allow us to access members of unexported structs reliably without having to export all these helper functions. It's been something I wanted to look into but no time yet. Thanks -- Qais Yousef > > #ifdef CONFIG_SMP > if (prev_nr < 2 && rq->nr_running >= 2) { > @@ -1973,6 +1983,8 @@ static inline void add_nr_running(struct rq *rq, unsigned count) > static inline void sub_nr_running(struct rq *rq, unsigned count) > { > rq->nr_running -= count; > + trace_sched_update_nr_running_tp(cpu_of(rq), -count, rq->nr_running); > + > /* Check if we still need preemption */ > sched_update_tick_dependency(rq); > } > -- > 2.18.0 >