lkml.org 
[lkml]   [2009]   [Sep]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[RFC][PATCH 08/14] sched: remove reciprocal for cpu_power
    Its a source of fail, also, now that cpu_power is dynamical, its a
    waste of time.

    before:
    <idle>-0 [000] 132.877936: find_busiest_group: avg_load: 0 group_load: 8241 power: 1

    after:
    bash-1689 [001] 137.862151: find_busiest_group: avg_load: 10636288 group_load: 10387 power: 1

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    [andreas.herrmann3@amd.com: remove include]
    ---
    include/linux/sched.h | 10 +----
    kernel/sched.c | 100 +++++++++++++++++---------------------------------
    2 files changed, 36 insertions(+), 74 deletions(-)
    Index: linux-2.6/kernel/sched.c
    ===================================================================
    --- linux-2.6.orig/kernel/sched.c
    +++ linux-2.6/kernel/sched.c
    @@ -120,30 +120,8 @@
    */
    #define RUNTIME_INF ((u64)~0ULL)

    -#ifdef CONFIG_SMP
    -
    static void double_rq_lock(struct rq *rq1, struct rq *rq2);

    -/*
    - * Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
    - * Since cpu_power is a 'constant', we can use a reciprocal divide.
    - */
    -static inline u32 sg_div_cpu_power(const struct sched_group *sg, u32 load)
    -{
    - return reciprocal_divide(load, sg->reciprocal_cpu_power);
    -}
    -
    -/*
    - * Each time a sched group cpu_power is changed,
    - * we must compute its reciprocal value
    - */
    -static inline void sg_inc_cpu_power(struct sched_group *sg, u32 val)
    -{
    - sg->__cpu_power += val;
    - sg->reciprocal_cpu_power = reciprocal_value(sg->__cpu_power);
    -}
    -#endif
    -
    static inline int rt_policy(int policy)
    {
    if (unlikely(policy == SCHED_FIFO || policy == SCHED_RR))
    @@ -2335,8 +2313,7 @@ find_idlest_group(struct sched_domain *s
    }

    /* Adjust by relative CPU power of the group */
    - avg_load = sg_div_cpu_power(group,
    - avg_load * SCHED_LOAD_SCALE);
    + avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;

    if (local_group) {
    this_load = avg_load;
    @@ -3768,7 +3745,6 @@ static void update_cpu_power(struct sche
    unsigned long weight = cpumask_weight(sched_domain_span(sd));
    unsigned long power = SCHED_LOAD_SCALE;
    struct sched_group *sdg = sd->groups;
    - unsigned long old = sdg->__cpu_power;

    /* here we could scale based on cpufreq */

    @@ -3783,33 +3759,26 @@ static void update_cpu_power(struct sche
    if (!power)
    power = 1;

    - if (power != old) {
    - sdg->__cpu_power = power;
    - sdg->reciprocal_cpu_power = reciprocal_value(power);
    - }
    + sdg->cpu_power = power;
    }

    static void update_group_power(struct sched_domain *sd, int cpu)
    {
    struct sched_domain *child = sd->child;
    struct sched_group *group, *sdg = sd->groups;
    - unsigned long power = sdg->__cpu_power;

    if (!child) {
    update_cpu_power(sd, cpu);
    return;
    }

    - sdg->__cpu_power = 0;
    + sdg->cpu_power = 0;

    group = child->groups;
    do {
    - sdg->__cpu_power += group->__cpu_power;
    + sdg->cpu_power += group->cpu_power;
    group = group->next;
    } while (group != child->groups);
    -
    - if (power != sdg->__cpu_power)
    - sdg->reciprocal_cpu_power = reciprocal_value(sdg->__cpu_power);
    }

    /**
    @@ -3889,8 +3858,7 @@ static inline void update_sg_lb_stats(st
    }

    /* Adjust by relative CPU power of the group */
    - sgs->avg_load = sg_div_cpu_power(group,
    - sgs->group_load * SCHED_LOAD_SCALE);
    + sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;


    /*
    @@ -3902,14 +3870,14 @@ static inline void update_sg_lb_stats(st
    * normalized nr_running number somewhere that negates
    * the hierarchy?
    */
    - avg_load_per_task = sg_div_cpu_power(group,
    - sum_avg_load_per_task * SCHED_LOAD_SCALE);
    + avg_load_per_task = (sum_avg_load_per_task * SCHED_LOAD_SCALE) /
    + group->cpu_power;

    if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
    sgs->group_imb = 1;

    sgs->group_capacity =
    - DIV_ROUND_CLOSEST(group->__cpu_power, SCHED_LOAD_SCALE);
    + DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
    }

    /**
    @@ -3951,7 +3919,7 @@ static inline void update_sd_lb_stats(st
    return;

    sds->total_load += sgs.group_load;
    - sds->total_pwr += group->__cpu_power;
    + sds->total_pwr += group->cpu_power;

    /*
    * In case the child domain prefers tasks go to siblings
    @@ -4016,28 +3984,28 @@ static inline void fix_small_imbalance(s
    * moving them.
    */

    - pwr_now += sds->busiest->__cpu_power *
    + pwr_now += sds->busiest->cpu_power *
    min(sds->busiest_load_per_task, sds->max_load);
    - pwr_now += sds->this->__cpu_power *
    + pwr_now += sds->this->cpu_power *
    min(sds->this_load_per_task, sds->this_load);
    pwr_now /= SCHED_LOAD_SCALE;

    /* Amount of load we'd subtract */
    - tmp = sg_div_cpu_power(sds->busiest,
    - sds->busiest_load_per_task * SCHED_LOAD_SCALE);
    + tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
    + sds->busiest->cpu_power;
    if (sds->max_load > tmp)
    - pwr_move += sds->busiest->__cpu_power *
    + pwr_move += sds->busiest->cpu_power *
    min(sds->busiest_load_per_task, sds->max_load - tmp);

    /* Amount of load we'd add */
    - if (sds->max_load * sds->busiest->__cpu_power <
    + if (sds->max_load * sds->busiest->cpu_power <
    sds->busiest_load_per_task * SCHED_LOAD_SCALE)
    - tmp = sg_div_cpu_power(sds->this,
    - sds->max_load * sds->busiest->__cpu_power);
    + tmp = (sds->max_load * sds->busiest->cpu_power) /
    + sds->this->cpu_power;
    else
    - tmp = sg_div_cpu_power(sds->this,
    - sds->busiest_load_per_task * SCHED_LOAD_SCALE);
    - pwr_move += sds->this->__cpu_power *
    + tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
    + sds->this->cpu_power;
    + pwr_move += sds->this->cpu_power *
    min(sds->this_load_per_task, sds->this_load + tmp);
    pwr_move /= SCHED_LOAD_SCALE;

    @@ -4072,8 +4040,8 @@ static inline void calculate_imbalance(s
    sds->max_load - sds->busiest_load_per_task);

    /* How much load to actually move to equalise the imbalance */
    - *imbalance = min(max_pull * sds->busiest->__cpu_power,
    - (sds->avg_load - sds->this_load) * sds->this->__cpu_power)
    + *imbalance = min(max_pull * sds->busiest->cpu_power,
    + (sds->avg_load - sds->this_load) * sds->this->cpu_power)
    / SCHED_LOAD_SCALE;

    /*
    @@ -4208,7 +4176,7 @@ static unsigned long power_of(int cpu)
    if (!group)
    return SCHED_LOAD_SCALE;

    - return group->__cpu_power;
    + return group->cpu_power;
    }

    /*
    @@ -7934,7 +7902,7 @@ static int sched_domain_debug_one(struct
    break;
    }

    - if (!group->__cpu_power) {
    + if (!group->cpu_power) {
    printk(KERN_CONT "\n");
    printk(KERN_ERR "ERROR: domain->cpu_power not "
    "set\n");
    @@ -7958,9 +7926,9 @@ static int sched_domain_debug_one(struct
    cpulist_scnprintf(str, sizeof(str), sched_group_cpus(group));

    printk(KERN_CONT " %s", str);
    - if (group->__cpu_power != SCHED_LOAD_SCALE) {
    - printk(KERN_CONT " (__cpu_power = %d)",
    - group->__cpu_power);
    + if (group->cpu_power != SCHED_LOAD_SCALE) {
    + printk(KERN_CONT " (cpu_power = %d)",
    + group->cpu_power);
    }

    group = group->next;
    @@ -8245,7 +8213,7 @@ init_sched_build_groups(const struct cpu
    continue;

    cpumask_clear(sched_group_cpus(sg));
    - sg->__cpu_power = 0;
    + sg->cpu_power = 0;

    for_each_cpu(j, span) {
    if (group_fn(j, cpu_map, NULL, tmpmask) != group)
    @@ -8503,7 +8471,7 @@ static void init_numa_sched_groups_power
    continue;
    }

    - sg_inc_cpu_power(sg, sd->groups->__cpu_power);
    + sg->cpu_power += sd->groups->cpu_power;
    }
    sg = sg->next;
    } while (sg != group_head);
    @@ -8540,7 +8508,7 @@ static int build_numa_sched_groups(struc
    sd->groups = sg;
    }

    - sg->__cpu_power = 0;
    + sg->cpu_power = 0;
    cpumask_copy(sched_group_cpus(sg), d->nodemask);
    sg->next = sg;
    cpumask_or(d->covered, d->covered, d->nodemask);
    @@ -8563,7 +8531,7 @@ static int build_numa_sched_groups(struc
    "Can not alloc domain group for node %d\n", j);
    return -ENOMEM;
    }
    - sg->__cpu_power = 0;
    + sg->cpu_power = 0;
    cpumask_copy(sched_group_cpus(sg), d->tmpmask);
    sg->next = prev->next;
    cpumask_or(d->covered, d->covered, d->tmpmask);
    @@ -8641,7 +8609,7 @@ static void init_sched_groups_power(int

    child = sd->child;

    - sd->groups->__cpu_power = 0;
    + sd->groups->cpu_power = 0;

    if (!child) {
    power = SCHED_LOAD_SCALE;
    @@ -8657,7 +8625,7 @@ static void init_sched_groups_power(int
    power /= weight;
    power >>= SCHED_LOAD_SHIFT;
    }
    - sg_inc_cpu_power(sd->groups, power);
    + sd->groups->cpu_power += power;
    return;
    }

    @@ -8666,7 +8634,7 @@ static void init_sched_groups_power(int
    */
    group = child->groups;
    do {
    - sg_inc_cpu_power(sd->groups, group->__cpu_power);
    + sd->groups->cpu_power += group->cpu_power;
    group = group->next;
    } while (group != child->groups);
    }
    Index: linux-2.6/include/linux/sched.h
    ===================================================================
    --- linux-2.6.orig/include/linux/sched.h
    +++ linux-2.6/include/linux/sched.h
    @@ -870,15 +870,9 @@ struct sched_group {

    /*
    * CPU power of this group, SCHED_LOAD_SCALE being max power for a
    - * single CPU. This is read only (except for setup, hotplug CPU).
    - * Note : Never change cpu_power without recompute its reciprocal
    + * single CPU.
    */
    - unsigned int __cpu_power;
    - /*
    - * reciprocal value of cpu_power to avoid expensive divides
    - * (see include/linux/reciprocal_div.h)
    - */
    - u32 reciprocal_cpu_power;
    + unsigned int cpu_power;

    /*
    * The CPUs this group covers.
    --



    \
     
     \ /
      Last update: 2009-09-03 15:27    [from the cache]
    ©2003-2011 Jasper Spaans