Add a topology flag to the sched_domain hierarchy indicating the lowest domain level where the full range of cpu capacities is represented by the domain members for asymmetric capacity topologies (e.g. ARM big.LITTLE).
The flag is intended to indicate that extra care should be taken when placing tasks on cpus and this level spans all the different types of cpus found in the system (no need to look further up the domain hierarchy). This information is currently only available through iterating through the capacities of all the cpus at parent levels in the sched_domain hierarchy. SD 2 [ 0 1 2 3] SD_ASYM_CPUCAPACITY SD 1 [ 0 1] [ 2 3] !SD_ASYM_CPUCAPACITY cpu: 0 1 2 3 capacity: 756 756 1024 1024 If the topology in the example above is duplicated to create an eight cpu example with third sched_domain level on top (SD 3), this level should not have the flag set (!SD_ASYM_CPUCAPACITY) as its two group would both have all cpu capacities represented within them. cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- include/linux/sched.h | 1 + kernel/sched/core.c | 6 +++++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 930784dd7cd8..4e0c47af9b05 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1021,6 +1021,7 @@ extern void wake_up_q(struct wake_q_head *head); #define SD_BALANCE_FORK 0x0008 /* Balance on fork, clone */ #define SD_BALANCE_WAKE 0x0010 /* Balance on wakeup */ #define SD_WAKE_AFFINE 0x0020 /* Wake task to waking CPU */ +#define SD_ASYM_CPUCAPACITY 0x0040 /* Groups have different max cpu capacities */ #define SD_SHARE_CPUCAPACITY 0x0080 /* Domain members share cpu capacity */ #define SD_SHARE_POWERDOMAIN 0x0100 /* Domain members share power domain */ #define SD_SHARE_PKG_RESOURCES 0x0200 /* Domain members share cpu pkg resources */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0a40beb46841..1a22fc9e3788 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5692,6 +5692,7 @@ static int sd_degenerate(struct sched_domain *sd) SD_BALANCE_FORK | SD_BALANCE_EXEC | SD_SHARE_CPUCAPACITY | + SD_ASYM_CPUCAPACITY | SD_SHARE_PKG_RESOURCES | SD_SHARE_POWERDOMAIN)) { if (sd->groups != sd->groups->next) @@ -5722,6 +5723,7 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent) SD_BALANCE_NEWIDLE | SD_BALANCE_FORK | SD_BALANCE_EXEC | + SD_ASYM_CPUCAPACITY | SD_SHARE_CPUCAPACITY | SD_SHARE_PKG_RESOURCES | SD_PREFER_SIBLING | @@ -6336,14 +6338,16 @@ static int sched_domains_curr_level; * SD_NUMA - describes NUMA topologies * SD_SHARE_POWERDOMAIN - describes shared power domain * - * Odd one out: + * Odd ones out: * SD_ASYM_PACKING - describes SMT quirks + * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies */ #define TOPOLOGY_SD_FLAGS \ (SD_SHARE_CPUCAPACITY | \ SD_SHARE_PKG_RESOURCES | \ SD_NUMA | \ SD_ASYM_PACKING | \ + SD_ASYM_CPUCAPACITY | \ SD_SHARE_POWERDOMAIN) static struct sched_domain * -- 1.9.1
