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mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate

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The PTE scanning rate and fault rates are two of the biggest sources of
system CPU overhead with automatic NUMA placement.  Ideally a proper policy
would detect if a workload was properly placed, schedule and adjust the
PTE scanning rate accordingly. We do not track the necessary information
to do that but we at least know if we migrated or not.

This patch scans slower if a page was not migrated as the result of a
NUMA hinting fault up to sysctl_numa_balancing_scan_period_max which is
now higher than the previous default. Once every minute it will reset
the scanner in case of phase changes.

This is hilariously crude and the numbers are arbitrary. Workloads will
converge quite slowly in comparison to what a proper policy should be able
to do. On the plus side, we will chew up less CPU for workloads that have
no need for automatic balancing.

Signed-off-by: Mel Gorman <mgorman@suse.de>
This commit is contained in:
Mel Gorman
2012-11-21 01:18:23 +00:00
parent e42c8ff299
commit b8593bfda1
7 changed files with 44 additions and 15 deletions
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5
include/linux/sched.h
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@@ -1562,9 +1562,9 @@ struct task_struct {
#define tsk_cpus_allowed(tsk) (&(tsk)->cpus_allowed)
#ifdef CONFIG_NUMA_BALANCING
extern void task_numa_fault(int node, int pages);
extern void task_numa_fault(int node, int pages, bool migrated);
#else
static inline void task_numa_fault(int node, int pages)
static inline void task_numa_fault(int node, int pages, bool migrated)
{
}
#endif
@@ -2009,6 +2009,7 @@ extern enum sched_tunable_scaling sysctl_sched_tunable_scaling;
extern unsigned int sysctl_numa_balancing_scan_delay;
extern unsigned int sysctl_numa_balancing_scan_period_min;
extern unsigned int sysctl_numa_balancing_scan_period_max;
extern unsigned int sysctl_numa_balancing_scan_period_reset;
extern unsigned int sysctl_numa_balancing_scan_size;
extern unsigned int sysctl_numa_balancing_settle_count;