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Message-Id: <20200701190656.10126-7-valentin.schneider@arm.com>
Date: Wed, 1 Jul 2020 20:06:54 +0100
From: Valentin Schneider <valentin.schneider@....com>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
morten.rasmussen@....com
Subject: [PATCH v3 6/7] sched/topology: Introduce SD metaflag for flags needing > 1 groups
In preparation of cleaning up the sd_degenerate*() functions, mark flags
that are only relevant when their associated domain has more than a single
group. With this, build a compile-time mask of those SD flags.
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
include/linux/sched/sd_flags.h | 60 ++++++++++++++++++++++------------
include/linux/sched/topology.h | 7 ++++
2 files changed, 47 insertions(+), 20 deletions(-)
diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h
index c0003b252d48..408832193a94 100644
--- a/include/linux/sched/sd_flags.h
+++ b/include/linux/sched/sd_flags.h
@@ -8,7 +8,7 @@
#endif
/*
- * Expected flag uses
+ * Hierarchical metaflags
*
* SHARED_CHILD: These flags are meant to be set from the base domain upwards.
* If a domain has this flag set, all of its children should have it set. This
@@ -29,36 +29,50 @@
* certain level (e.g. domain starts spanning CPUs outside of the base CPU's
* socket).
*/
-#define SDF_SHARED_CHILD 0x1
-#define SDF_SHARED_PARENT 0x2
+#define SDF_SHARED_CHILD 0x1
+#define SDF_SHARED_PARENT 0x2
+
+/*
+ * Behavioural metaflags
+ *
+ * NEEDS_GROUPS: These flags are only relevant if the domain they are set on has
+ * more than one group. This is usually for balancing flags (load balancing
+ * involves equalizing a metric between groups), or for flags describing some
+ * shared resource (which would be shared between groups).
+ */
+#define SDF_NEEDS_GROUPS 0x4
/*
* Balance when about to become idle
*
* SHARED_CHILD: Set from the base domain up to cpuset.sched_relax_domain_level.
+ * NEEDS_GROUPS: Load balancing flag.
*/
-SD_FLAG(SD_BALANCE_NEWIDLE, 0, SDF_SHARED_CHILD)
+SD_FLAG(SD_BALANCE_NEWIDLE, 0, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Balance on exec
*
* SHARED_CHILD: Set from the base domain up to the NUMA reclaim level.
+ * NEEDS_GROUPS: Load balancing flag.
*/
-SD_FLAG(SD_BALANCE_EXEC, 1, SDF_SHARED_CHILD)
+SD_FLAG(SD_BALANCE_EXEC, 1, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Balance on fork, clone
*
* SHARED_CHILD: Set from the base domain up to the NUMA reclaim level.
+ * NEEDS_GROUPS: Load balancing flag.
*/
-SD_FLAG(SD_BALANCE_FORK, 2, SDF_SHARED_CHILD)
+SD_FLAG(SD_BALANCE_FORK, 2, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Balance on wakeup
*
* SHARED_CHILD: Set from the base domain up to cpuset.sched_relax_domain_level.
+ * NEEDS_GROUPS: Load balancing flag.
*/
-SD_FLAG(SD_BALANCE_WAKE, 3, SDF_SHARED_CHILD)
+SD_FLAG(SD_BALANCE_WAKE, 3, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Consider waking task on waking CPU.
@@ -71,33 +85,36 @@ SD_FLAG(SD_WAKE_AFFINE, 4, SDF_SHARED_CHILD)
* Domain members have different CPU capacities
*
* SHARED_PARENT: Set from the topmost domain down to the first domain where
- * asymmetry is detected.
+ * asymmetry is detected.
+ * NEEDS_GROUPS: Per-CPU capacity is asymmetric between groups.
*/
-SD_FLAG(SD_ASYM_CPUCAPACITY, 5, SDF_SHARED_PARENT)
+SD_FLAG(SD_ASYM_CPUCAPACITY, 5, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)
/*
* Domain members share CPU capacity (i.e. SMT)
*
* SHARED_CHILD: Set from the base domain up until spanned CPUs no longer share
- * CPU capacity.
+ * CPU capacity.
+ * NEEDS_GROUPS: Capacity is shared between groups.
*/
-SD_FLAG(SD_SHARE_CPUCAPACITY, 6, SDF_SHARED_CHILD)
+SD_FLAG(SD_SHARE_CPUCAPACITY, 6, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Domain members share CPU package resources (i.e. caches)
*
* SHARED_CHILD: Set from the base domain up until spanned CPUs no longer share
- * the same cache(s).
+ * the same cache(s).
+ * NEEDS_GROUPS: Caches are shared between groups.
*/
-SD_FLAG(SD_SHARE_PKG_RESOURCES, 7, SDF_SHARED_CHILD)
+SD_FLAG(SD_SHARE_PKG_RESOURCES, 7, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Only a single load balancing instance
*
* SHARED_PARENT: Set for all NUMA levels above NODE. Could be set from a
- * different level upwards, but it doesn't change that if a domain has this flag
- * set, then all of its parents need to have it too (otherwise the serialization
- * doesn't make sense).
+ * different level upwards, but it doesn't change that if a
+ * domain has this flag set, then all of its parents need to have
+ * it too (otherwise the serialization doesn't make sense).
*/
SD_FLAG(SD_SERIALIZE, 8, SDF_SHARED_PARENT)
@@ -105,16 +122,18 @@ SD_FLAG(SD_SERIALIZE, 8, SDF_SHARED_PARENT)
* Place busy tasks earlier in the domain
*
* SHARED_CHILD: Usually set on the SMT level. Technically could be set further
- * up, but currently assumed to be set from the base domain upwards (see
- * update_top_cache_domain()).
+ * up, but currently assumed to be set from the base domain
+ * upwards (see update_top_cache_domain()).
*/
-SD_FLAG(SD_ASYM_PACKING, 9, SDF_SHARED_CHILD)
+SD_FLAG(SD_ASYM_PACKING, 9, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
/*
* Prefer to place tasks in a sibling domain
*
* Set up until domains start spanning NUMA nodes. Close to being a SHARED_CHILD
* flag, but cleared below domains with SD_ASYM_CPUCAPACITY.
+ *
+ * NEEDS_GROUPS: Load balancing flag.
*/
SD_FLAG(SD_PREFER_SIBLING, 10, 0)
@@ -122,8 +141,9 @@ SD_FLAG(SD_PREFER_SIBLING, 10, 0)
* sched_groups of this level overlap
*
* SHARED_PARENT: Set for all NUMA levels above NODE.
+ * NEEDS_GROUPS: Overlaps can only exist with more than one group.
*/
-SD_FLAG(SD_OVERLAP, 11, SDF_SHARED_PARENT)
+SD_FLAG(SD_OVERLAP, 11, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)
/*
* cross-node balancing
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index fce64dae09af..a6761d5d66dd 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -16,6 +16,13 @@
#include <linux/sched/sd_flags.h>
#undef SD_FLAG
+/* Generate a mask of SD flags with the SDF_NEEDS_GROUPS metaflag */
+#define SD_FLAG(name, idx, mflags) (BIT(idx) * (((mflags) & SDF_NEEDS_GROUPS) / SDF_NEEDS_GROUPS)) |
+static const int SD_DEGENERATE_GROUPS_MASK =
+#include<linux/sched/sd_flags.h>
+0;
+#undef SD_FLAG
+
#ifdef CONFIG_SCHED_DEBUG
#define SD_FLAG(_name, idx, mflags) [idx] = {.meta_flags = mflags, .name = #_name},
static const struct {
--
2.27.0
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