Messages in this thread Patch in this message |  | | From | Morten Rasmussen <> | Subject | [PATCH] sched/topology: Set SD_PREFER_SIBLING consistently on non-NUMA levels | Date | Mon, 27 Nov 2017 17:29:27 +0000 |
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SD_PREFER_SIBLING adds an additional bias towards spreading tasks on the _parent_ sched_domain even if a sched_group isn't overloaded. It is currently set on:
1. SMT level to promote spreading to sibling cores rather than using sibling HW-threads (caff37ef96eac7fe96a).
2. Non-NUMA levels which don't have the SD_SHARE_PKG_RESOURCES flag set (= DIE level in the default topology) as it was found to improve benchmarks on certain NUMA systems (6956dc568f34107f1d02b).
3. Any non-NUMA level that inherits the flag due to elimination of its parent sched_domain level in the de-generate step of the sched_domain hierarchy set up (= MC level in the default topology).
Preferring siblings seems to be a useful tweak for all non-NUMA levels, so we should enable it on all non-NUMA levels. As it is, it is possible to have it SMT and DIE, but not MC in between when using the default topology.
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> cc: Ingo Molnar <mingo@redhat.com> cc: Peter Zijlstra <peterz@infradead.org> --- kernel/sched/topology.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 6798276d29af..7f70806bfa0f 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1122,7 +1122,7 @@ sd_init(struct sched_domain_topology_level *tl, | 0*SD_SHARE_CPUCAPACITY | 0*SD_SHARE_PKG_RESOURCES | 0*SD_SERIALIZE - | 0*SD_PREFER_SIBLING + | 1*SD_PREFER_SIBLING | 0*SD_NUMA | sd_flags , @@ -1153,7 +1153,6 @@ sd_init(struct sched_domain_topology_level *tl, } if (sd->flags & SD_SHARE_CPUCAPACITY) { - sd->flags |= SD_PREFER_SIBLING; sd->imbalance_pct = 110; sd->smt_gain = 1178; /* ~15% */ @@ -1168,6 +1167,7 @@ sd_init(struct sched_domain_topology_level *tl, sd->busy_idx = 3; sd->idle_idx = 2; + sd->flags &= ~SD_PREFER_SIBLING; sd->flags |= SD_SERIALIZE; if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) { sd->flags &= ~(SD_BALANCE_EXEC | @@ -1177,7 +1177,6 @@ sd_init(struct sched_domain_topology_level *tl, #endif } else { - sd->flags |= SD_PREFER_SIBLING; sd->cache_nice_tries = 1; sd->busy_idx = 2; sd->idle_idx = 1; -- 2.7.4
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