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    Subject[PATCH 12/19] sched:numa Remove numa_has_capacity
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    task_numa_find_cpu helps to find the cpu to swap/move the task.
    Its guarded by numa_has_capacity(). However node not having capacity
    shouldn't deter a task swapping if it helps numa placement.

    Further load_too_imbalanced, which evaluates possibilities of move/swap,
    provides similar checks as numa_has_capacity.

    Hence remove numa_has_capacity() to enhance possibilities of task
    swapping even if load is imbalanced.

    Testcase Time: Min Max Avg StdDev
    numa01.sh Real: 674.61 997.71 785.01 115.95
    numa01.sh Sys: 180.87 318.88 270.13 51.32
    numa01.sh User: 54001.30 71936.50 60495.48 6237.55
    numa02.sh Real: 60.62 62.30 61.46 0.62
    numa02.sh Sys: 15.01 33.63 24.38 6.81
    numa02.sh User: 5234.20 5325.60 5276.23 38.85
    numa03.sh Real: 827.62 946.85 914.48 44.58
    numa03.sh Sys: 135.55 172.40 158.46 12.75
    numa03.sh User: 64839.42 73195.44 70805.96 3061.20
    numa04.sh Real: 481.01 608.76 521.14 47.28
    numa04.sh Sys: 329.59 373.15 353.20 14.20
    numa04.sh User: 37649.09 40722.94 38806.32 1072.32
    numa05.sh Real: 399.21 415.38 409.88 5.54
    numa05.sh Sys: 319.46 418.57 363.31 37.62
    numa05.sh User: 33727.77 34732.68 34127.41 447.11

    Testcase Time: Min Max Avg StdDev %Change
    numa01.sh Real: 435.67 707.28 527.49 97.85 48.81%
    numa01.sh Sys: 76.41 231.19 162.49 56.13 66.24%
    numa01.sh User: 38247.36 59033.52 45129.31 7642.69 34.04%
    numa02.sh Real: 60.35 62.09 61.09 0.69 0.605%
    numa02.sh Sys: 15.01 30.20 20.64 5.56 18.12%
    numa02.sh User: 5195.93 5294.82 5240.99 40.55 0.672%
    numa03.sh Real: 752.04 919.89 836.81 63.29 9.281%
    numa03.sh Sys: 115.10 133.35 125.46 7.78 26.30%
    numa03.sh User: 58736.44 70084.26 65103.67 4416.10 8.758%
    numa04.sh Real: 418.43 709.69 512.53 104.17 1.679%
    numa04.sh Sys: 242.99 370.47 297.39 42.20 18.76%
    numa04.sh User: 34916.14 48429.54 38955.65 4928.05 -0.38%
    numa05.sh Real: 379.27 434.05 403.70 17.79 1.530%
    numa05.sh Sys: 145.94 344.50 268.72 68.53 35.20%
    numa05.sh User: 32679.32 35449.75 33989.10 913.19 0.406%

    Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    ---
    kernel/sched/fair.c | 37 +++----------------------------------
    1 file changed, 3 insertions(+), 34 deletions(-)

    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index 259c343..709c77c 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -1417,7 +1417,6 @@ struct numa_stats {
    unsigned long compute_capacity;

    unsigned int nr_running;
    - int has_free_capacity;
    };

    /*
    @@ -1444,8 +1443,7 @@ static void update_numa_stats(struct numa_stats *ns, int nid)
    * the @ns structure is NULL'ed and task_numa_compare() will
    * not find this node attractive.
    *
    - * We'll either bail at !has_free_capacity, or we'll detect a huge
    - * imbalance and bail there.
    + * We'll detect a huge imbalance and bail there.
    */
    if (!cpus)
    return;
    @@ -1456,7 +1454,6 @@ static void update_numa_stats(struct numa_stats *ns, int nid)

    capacity = min_t(unsigned, capacity,
    DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
    - ns->has_free_capacity = (ns->nr_running < capacity);
    }

    struct task_numa_env {
    @@ -1672,7 +1669,6 @@ static void task_numa_find_cpu(struct task_numa_env *env,
    * than swapping tasks around, check if a move is possible.
    */
    move = !load_too_imbalanced(src_load, dst_load, env);
    -
    for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
    /* Skip this CPU if the source task cannot migrate */
    if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
    @@ -1683,31 +1679,6 @@ static void task_numa_find_cpu(struct task_numa_env *env,
    }
    }

    -/* Only move tasks to a NUMA node less busy than the current node. */
    -static bool numa_has_capacity(struct task_numa_env *env)
    -{
    - struct numa_stats *src = &env->src_stats;
    - struct numa_stats *dst = &env->dst_stats;
    -
    - if (src->has_free_capacity && !dst->has_free_capacity)
    - return false;
    -
    - /*
    - * Only consider a task move if the source has a higher load
    - * than the destination, corrected for CPU capacity on each node.
    - *
    - * src->load dst->load
    - * --------------------- vs ---------------------
    - * src->compute_capacity dst->compute_capacity
    - */
    - if (src->load * dst->compute_capacity * env->imbalance_pct >
    -
    - dst->load * src->compute_capacity * 100)
    - return true;
    -
    - return false;
    -}
    -
    static int task_numa_migrate(struct task_struct *p)
    {
    struct task_numa_env env = {
    @@ -1764,8 +1735,7 @@ static int task_numa_migrate(struct task_struct *p)
    update_numa_stats(&env.dst_stats, env.dst_nid);

    /* Try to find a spot on the preferred nid. */
    - if (numa_has_capacity(&env))
    - task_numa_find_cpu(&env, taskimp, groupimp);
    + task_numa_find_cpu(&env, taskimp, groupimp);

    /*
    * Look at other nodes in these cases:
    @@ -1795,8 +1765,7 @@ static int task_numa_migrate(struct task_struct *p)
    env.dist = dist;
    env.dst_nid = nid;
    update_numa_stats(&env.dst_stats, env.dst_nid);
    - if (numa_has_capacity(&env))
    - task_numa_find_cpu(&env, taskimp, groupimp);
    + task_numa_find_cpu(&env, taskimp, groupimp);
    }
    }

    --
    1.8.3.1
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