Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | [PATCH v4 09/10] sched/topology: Introduce SD metaflag for flags needing > 1 groups | Date | Fri, 31 Jul 2020 12:55:01 +0100 |
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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@infradead.org> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- include/linux/sched/sd_flags.h | 69 ++++++++++++++++++++++------------ include/linux/sched/topology.h | 7 ++++ 2 files changed, 53 insertions(+), 23 deletions(-)
diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h index 9d0fb8924181..6c70af066995 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. @@ -71,63 +85,72 @@ 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). + * NEEDS_GROUPS: No point in preserving domain if it has a single group. */ -SD_FLAG(SD_SERIALIZE, 8, SDF_SHARED_PARENT) +SD_FLAG(SD_SERIALIZE, 8, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) /* * 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()). + * NEEDS_GROUPS: Load balancing flag. */ -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) +SD_FLAG(SD_PREFER_SIBLING, 10, SDF_NEEDS_GROUPS) /* * 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 * * SHARED_PARENT: Set for all NUMA levels above NODE. + * NEEDS_GROUPS: No point in preserving domain if it has a single group. */ -SD_FLAG(SD_NUMA, 12, SDF_SHARED_PARENT) +SD_FLAG(SD_NUMA, 12, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 99b16d4c03f2..74e6ec32a413 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)) | +static const unsigned 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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