| Message ID | 1406569906-9763-9-git-send-email-vincent.guittot@linaro.org |
|---|---|
| State | New |
| Headers | show |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/28/2014 01:51 PM, Vincent Guittot wrote: > If the CPU is used for handling lot of IRQs, trig a load balance to > check if it's worth moving its tasks on another CPU that has more > capacity. > > As a sidenote, this will note generate more spurious ilb because we > already trig an ilb if there is more than 1 busy cpu. If this cpu > is the only one that has a task, we will trig the ilb once for > migrating the task. > > The nohz_kick_needed function has been cleaned up a bit while > adding the new test > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> --- > kernel/sched/fair.c | 69 > +++++++++++++++++++++++++++++++++++++---------------- 1 file > changed, 49 insertions(+), 20 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index > 6843016..1cde8dd 100644 --- a/kernel/sched/fair.c +++ > b/kernel/sched/fair.c @@ -5969,6 +5969,14 @@ static bool > update_sd_pick_busiest(struct lb_env *env, return true; } > > + /* + * The group capacity is reduced probably because of > activity from other + * sched class or interrupts which use part > of the available capacity + */ + if ((sg->sgc->capacity_orig * > 100) > (sgs->group_capacity * + env->sd->imbalance_pct)) + > return true; + return false; } Isn't this already reflected in avg_load, by having avg_load increase due to the capacity decreasing when a cpu is busy with non-CFS loads? Also, this part of update_sd_pick_busiest will not be reached in the !SD_ASYM_PACKING case once my patch is applied, so this is a small conflict between our series :) - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJT1pm+AAoJEM553pKExN6DysEH/1/s2dY0EWM4mVctRAcyASc+ qD5yQgDZEbnIzuUldtTRNwlAxHSaexLI7oF418RAaUV3oue+OQIesJPhKDVrR2+J fLo4fhtutuF1SHJ5Zo2fiGBIUI+GuLspT2fXiG2UxXQXtYioVdDeB+cjo6H3xQ3D R2hR+WeSsLznwFhRnufI1neleIRpqk/Nw1wfdXCyE03kM478rCQjlygMUx6eqURn jblr7GY7jmtzhYFPY9qnE0za/WHWUVAf4RXSjCcuYwZqdhbzmHPKpJyiC3cl9XGz kNzAjqVzvSyCBblaOnJfrRyCWmBdatp5eZQCzZK9/l+YpbkkzQJNlUMAAVV1eNw= =qD2A -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 28 July 2014 20:43, Rik van Riel <riel@redhat.com> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 07/28/2014 01:51 PM, Vincent Guittot wrote: >> If the CPU is used for handling lot of IRQs, trig a load balance to >> check if it's worth moving its tasks on another CPU that has more >> capacity. >> >> As a sidenote, this will note generate more spurious ilb because we >> already trig an ilb if there is more than 1 busy cpu. If this cpu >> is the only one that has a task, we will trig the ilb once for >> migrating the task. >> >> The nohz_kick_needed function has been cleaned up a bit while >> adding the new test >> >> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> --- >> kernel/sched/fair.c | 69 >> +++++++++++++++++++++++++++++++++++++---------------- 1 file >> changed, 49 insertions(+), 20 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index >> 6843016..1cde8dd 100644 --- a/kernel/sched/fair.c +++ >> b/kernel/sched/fair.c @@ -5969,6 +5969,14 @@ static bool >> update_sd_pick_busiest(struct lb_env *env, return true; } >> >> + /* + * The group capacity is reduced probably because of >> activity from other + * sched class or interrupts which use part >> of the available capacity + */ + if ((sg->sgc->capacity_orig * >> 100) > (sgs->group_capacity * + env->sd->imbalance_pct)) + >> return true; + return false; } > > Isn't this already reflected in avg_load, by having avg_load increase > due to the capacity decreasing when a cpu is busy with non-CFS loads? Yes, the avg_load should probably increase but it doesn't mean that it will be selected for a load balancing. > > Also, this part of update_sd_pick_busiest will not be reached in the > !SD_ASYM_PACKING case once my patch is applied, so this is a small > conflict between our series :) yes, this will conflict with your change but the conflict should be obvious to solve as it only adds a new condition for picking the group > > - -- > All rights reversed > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1 > Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ > > iQEcBAEBAgAGBQJT1pm+AAoJEM553pKExN6DysEH/1/s2dY0EWM4mVctRAcyASc+ > qD5yQgDZEbnIzuUldtTRNwlAxHSaexLI7oF418RAaUV3oue+OQIesJPhKDVrR2+J > fLo4fhtutuF1SHJ5Zo2fiGBIUI+GuLspT2fXiG2UxXQXtYioVdDeB+cjo6H3xQ3D > R2hR+WeSsLznwFhRnufI1neleIRpqk/Nw1wfdXCyE03kM478rCQjlygMUx6eqURn > jblr7GY7jmtzhYFPY9qnE0za/WHWUVAf4RXSjCcuYwZqdhbzmHPKpJyiC3cl9XGz > kNzAjqVzvSyCBblaOnJfrRyCWmBdatp5eZQCzZK9/l+YpbkkzQJNlUMAAVV1eNw= > =qD2A > -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6843016..1cde8dd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5969,6 +5969,14 @@ static bool update_sd_pick_busiest(struct lb_env *env, return true; } + /* + * The group capacity is reduced probably because of activity from other + * sched class or interrupts which use part of the available capacity + */ + if ((sg->sgc->capacity_orig * 100) > (sgs->group_capacity * + env->sd->imbalance_pct)) + return true; + return false; } @@ -6455,13 +6463,23 @@ static int need_active_balance(struct lb_env *env) struct sched_domain *sd = env->sd; if (env->idle == CPU_NEWLY_IDLE) { + int src_cpu = env->src_cpu; /* * ASYM_PACKING needs to force migrate tasks from busy but * higher numbered CPUs in order to pack all tasks in the * lowest numbered CPUs. */ - if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) + if ((sd->flags & SD_ASYM_PACKING) && src_cpu > env->dst_cpu) + return 1; + + /* + * If the CPUs share their cache and the src_cpu's capacity is + * reduced because of other sched_class or IRQs, we trig an + * active balance to move the task + */ + if ((capacity_orig_of(src_cpu) * 100) > (capacity_of(src_cpu) * + sd->imbalance_pct)) return 1; } @@ -6563,6 +6581,8 @@ static int load_balance(int this_cpu, struct rq *this_rq, schedstat_add(sd, lb_imbalance[idle], env.imbalance); + env.src_cpu = busiest->cpu; + ld_moved = 0; if (busiest->nr_running > 1) { /* @@ -6572,7 +6592,6 @@ static int load_balance(int this_cpu, struct rq *this_rq, * correctly treated as an imbalance. */ env.flags |= LBF_ALL_PINNED; - env.src_cpu = busiest->cpu; env.src_rq = busiest; env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); @@ -7262,10 +7281,12 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) /* * Current heuristic for kicking the idle load balancer in the presence - * of an idle cpu is the system. + * of an idle cpu in the system. * - This rq has more than one task. - * - At any scheduler domain level, this cpu's scheduler group has multiple - * busy cpu's exceeding the group's capacity. + * - This rq has at least one CFS task and the capacity of the CPU is + * significantly reduced because of RT tasks or IRQs. + * - At parent of LLC scheduler domain level, this cpu's scheduler group has + * multiple busy cpu. * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler * domain span are idle. */ @@ -7275,9 +7296,10 @@ static inline int nohz_kick_needed(struct rq *rq) struct sched_domain *sd; struct sched_group_capacity *sgc; int nr_busy, cpu = rq->cpu; + bool kick = false; if (unlikely(rq->idle_balance)) - return 0; + return false; /* * We may be recently in ticked or tickless idle mode. At the first @@ -7291,38 +7313,45 @@ static inline int nohz_kick_needed(struct rq *rq) * balancing. */ if (likely(!atomic_read(&nohz.nr_cpus))) - return 0; + return false; if (time_before(now, nohz.next_balance)) - return 0; + return false; if (rq->nr_running >= 2) - goto need_kick; + return true; rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_busy, cpu)); - if (sd) { sgc = sd->groups->sgc; nr_busy = atomic_read(&sgc->nr_busy_cpus); - if (nr_busy > 1) - goto need_kick_unlock; + if (nr_busy > 1) { + kick = true; + goto unlock; + } + } - sd = rcu_dereference(per_cpu(sd_asym, cpu)); + sd = rcu_dereference(rq->sd); + if (sd) { + if ((rq->cfs.h_nr_running >= 1) && + ((rq->cpu_capacity * sd->imbalance_pct) < + (rq->cpu_capacity_orig * 100))) { + kick = true; + goto unlock; + } + } + sd = rcu_dereference(per_cpu(sd_asym, cpu)); if (sd && (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)) - goto need_kick_unlock; + kick = true; +unlock: rcu_read_unlock(); - return 0; - -need_kick_unlock: - rcu_read_unlock(); -need_kick: - return 1; + return kick; } #else static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
If the CPU is used for handling lot of IRQs, trig a load balance to check if it's worth moving its tasks on another CPU that has more capacity. As a sidenote, this will note generate more spurious ilb because we already trig an ilb if there is more than 1 busy cpu. If this cpu is the only one that has a task, we will trig the ilb once for migrating the task. The nohz_kick_needed function has been cleaned up a bit while adding the new test Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> --- kernel/sched/fair.c | 69 +++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 49 insertions(+), 20 deletions(-)