Re: [PATCH v5 2/6] sched/topology: Introduce sched_group::flags
From: Vincent Guittot <vincent.guittot@linaro.org>
Date: 2021-09-17 15:26:17
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On Sat, 11 Sept 2021 at 03:19, Ricardo Neri [off-list ref] wrote:
There exist situations in which the load balance needs to know the properties of the CPUs in a scheduling group. When using asymmetric packing, for instance, the load balancer needs to know not only the state of dst_cpu but also of its SMT siblings, if any. Use the flags of the child scheduling domains to initialize scheduling group flags. This will reflect the properties of the CPUs in the group. A subsequent changeset will make use of these new flags. No functional changes are introduced. Cc: Aubrey Li <redacted> Cc: Ben Segall <bsegall@google.com> Cc: Daniel Bristot de Oliveira <redacted> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Quentin Perret <redacted> Cc: Rafael J. Wysocki <redacted> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tim Chen <redacted> Reviewed-by: Joel Fernandes (Google) <redacted> Reviewed-by: Len Brown <redacted> Originally-by: Peter Zijlstra (Intel) [off-list ref] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ricardo Neri <redacted>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
quoted hunk ↗ jump to hunk
--- Changes since v4: * None Changes since v3: * Clear the flags of the scheduling groups of a domain if its child is destroyed. * Minor rewording of the commit message. Changes since v2: * Introduced this patch. Changes since v1: * N/A --- kernel/sched/sched.h | 1 + kernel/sched/topology.c | 21 ++++++++++++++++++--- 2 files changed, 19 insertions(+), 3 deletions(-)diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 3d3e5793e117..86ab33ce529d 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h@@ -1809,6 +1809,7 @@ struct sched_group { unsigned int group_weight; struct sched_group_capacity *sgc; int asym_prefer_cpu; /* CPU of highest priority in group */ + int flags; /* * The CPUs this group covers.diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 4e8698e62f07..c56faae461d9 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c@@ -716,8 +716,20 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu) tmp = sd; sd = sd->parent; destroy_sched_domain(tmp); - if (sd) + if (sd) { + struct sched_group *sg = sd->groups; + + /* + * sched groups hold the flags of the child sched + * domain for convenience. Clear such flags since + * the child is being destroyed. + */ + do { + sg->flags = 0; + } while (sg != sd->groups); + sd->child = NULL; + } } for (tmp = sd; tmp; tmp = tmp->parent)@@ -916,10 +928,12 @@ build_group_from_child_sched_domain(struct sched_domain *sd, int cpu) return NULL; sg_span = sched_group_span(sg); - if (sd->child) + if (sd->child) { cpumask_copy(sg_span, sched_domain_span(sd->child)); - else + sg->flags = sd->child->flags; + } else { cpumask_copy(sg_span, sched_domain_span(sd)); + } atomic_inc(&sg->ref); return sg;@@ -1169,6 +1183,7 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd) if (child) { cpumask_copy(sched_group_span(sg), sched_domain_span(child)); cpumask_copy(group_balance_mask(sg), sched_group_span(sg)); + sg->flags = child->flags; } else { cpumask_set_cpu(cpu, sched_group_span(sg)); cpumask_set_cpu(cpu, group_balance_mask(sg)); --2.17.1