* Mel Gorman <mgor...@suse.de> [2013-06-26 15:38:01]:
> This patch tracks what nodes numa hinting faults were incurred on. Greater
> weight is given if the pages were to be migrated on the understanding
> that such faults cost significantly more. If a task has paid the cost to
> migrating data to that node then in the future it would be preferred if the
> task did not migrate the data again unnecessarily. This information is later
> used to schedule a task on the node incurring the most NUMA hinting faults.
>
> Signed-off-by: Mel Gorman <mgor...@suse.de>
> ---
> include/linux/sched.h | 2 ++
> kernel/sched/core.c | 3 +++
> kernel/sched/fair.c | 12 +++++++++++-
> kernel/sched/sched.h | 12 ++++++++++++
> 4 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e692a02..72861b4 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1505,6 +1505,8 @@ struct task_struct {
> unsigned int numa_scan_period;
> u64 node_stamp; /* migration stamp */
> struct callback_head numa_work;
> +
> + unsigned long *numa_faults;
> #endif /* CONFIG_NUMA_BALANCING */
>
> struct rcu_head rcu;
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 67d0465..f332ec0 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1594,6 +1594,7 @@ static void __sched_fork(struct task_struct *p)
> p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0;
> p->numa_scan_period = sysctl_numa_balancing_scan_delay;
> p->numa_work.next = &p->numa_work;
> + p->numa_faults = NULL;
> #endif /* CONFIG_NUMA_BALANCING */
> }
>
> @@ -1853,6 +1854,8 @@ static void finish_task_switch(struct rq *rq, struct
> task_struct *prev)
> if (mm)
> mmdrop(mm);
> if (unlikely(prev_state == TASK_DEAD)) {
> + task_numa_free(prev);
> +
> /*
> * Remove function-return probe instances associated with this
> * task and put them back on the free list.
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 7a33e59..904fd6f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -815,7 +815,14 @@ void task_numa_fault(int node, int pages, bool migrated)
> if (!sched_feat_numa(NUMA))
> return;
>
> - /* FIXME: Allocate task-specific structure for placement policy here */
> + /* Allocate buffer to track faults on a per-node basis */
> + if (unlikely(!p->numa_faults)) {
> + int size = sizeof(*p->numa_faults) * nr_node_ids;
> +
> + p->numa_faults = kzalloc(size, GFP_KERNEL);
> + if (!p->numa_faults)
> + return;
> + }
>
> /*
> * If pages are properly placed (did not migrate) then scan slower.
> @@ -826,6 +833,9 @@ void task_numa_fault(int node, int pages, bool migrated)
> p->numa_scan_period + jiffies_to_msecs(10));
>
> task_numa_placement(p);
> +
> + /* Record the fault, double the weight if pages were migrated */
> + p->numa_faults[node] += pages << migrated;
Why are we doing this after the placement.
I mean we should probably be doing this in the task_numa_placement,
Since doubling the pages can have an effect on the preferred node. If we
do it here, wont it end up in a case where the numa_faults on one node
is actually higher but it may end up being not the preferred node?
> }
>
> static void reset_ptenuma_scan(struct task_struct *p)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index cc03cfd..9c26d88 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -503,6 +503,18 @@ DECLARE_PER_CPU(struct rq, runqueues);
> #define cpu_curr(cpu) (cpu_rq(cpu)->curr)
> #define raw_rq() (&__raw_get_cpu_var(runqueues))
>
> +#ifdef CONFIG_NUMA_BALANCING
> +extern void sched_setnuma(struct task_struct *p, int node, int shared);
> +static inline void task_numa_free(struct task_struct *p)
> +{
> + kfree(p->numa_faults);
> +}
> +#else /* CONFIG_NUMA_BALANCING */
> +static inline void task_numa_free(struct task_struct *p)
> +{
> +}
> +#endif /* CONFIG_NUMA_BALANCING */
> +
> #ifdef CONFIG_SMP
>
> #define rcu_dereference_check_sched_domain(p) \
> --
> 1.8.1.4
>
> --
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--
Thanks and Regards
Srikar Dronamraju
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