diff options
author | Ingo Molnar <mingo@kernel.org> | 2023-10-06 12:25:16 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2023-10-09 12:21:23 +0200 |
commit | 7ef7145a2b26b172ac6885c4cf3272a38bc0979a (patch) | |
tree | 1f2b0b239664ade8b7525b33881b1ec10eed553a /kernel/sched | |
parent | bc87127a45928de5fdf0ec39d7a86e1edd0e179e (diff) |
sched/nohz: Update idle load-balancing (ILB) comments
- Fix incorrect/misleading comments,
- clarify some others,
- fix typos & grammar,
- and use more consistent style throughout.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/r/20231006102518.2452758-2-mingo@kernel.org
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/fair.c | 30 |
1 files changed, 16 insertions, 14 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 52c498fd6c46..2b63a14cd05e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -11503,14 +11503,15 @@ static inline int on_null_domain(struct rq *rq) #ifdef CONFIG_NO_HZ_COMMON /* - * idle load balancing details - * - When one of the busy CPUs notice that there may be an idle rebalancing + * NOHZ idle load balancing (ILB) details: + * + * - When one of the busy CPUs notices that there may be an idle rebalancing * needed, they will kick the idle load balancer, which then does idle * load balancing for all the idle CPUs. - * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED not set + * + * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED is not set * anywhere yet. */ - static inline int find_new_ilb(void) { int ilb; @@ -11531,8 +11532,10 @@ static inline int find_new_ilb(void) } /* - * Kick a CPU to do the nohz balancing, if it is time for it. We pick any - * idle CPU in the HK_TYPE_MISC housekeeping set (if there is one). + * Kick a CPU to do the NOHZ balancing, if it is time for it, via a cross-CPU + * SMP function call (IPI). + * + * We pick the first idle CPU in the HK_TYPE_MISC housekeeping set (if there is one). */ static void kick_ilb(unsigned int flags) { @@ -11560,7 +11563,7 @@ static void kick_ilb(unsigned int flags) /* * This way we generate an IPI on the target CPU which - * is idle. And the softirq performing nohz idle load balance + * is idle, and the softirq performing NOHZ idle load balancing * will be run before returning from the IPI. */ smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd); @@ -11589,7 +11592,7 @@ static void nohz_balancer_kick(struct rq *rq) /* * None are in tickless mode and hence no need for NOHZ idle load - * balancing. + * balancing: */ if (likely(!atomic_read(&nohz.nr_cpus))) return; @@ -11611,9 +11614,8 @@ static void nohz_balancer_kick(struct rq *rq) sd = rcu_dereference(rq->sd); if (sd) { /* - * If there's a CFS task and the current CPU has reduced - * capacity; kick the ILB to see if there's a better CPU to run - * on. + * If there's a runnable CFS task and the current CPU has reduced + * capacity, kick the ILB to see if there's a better CPU to run on: */ if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; @@ -11665,11 +11667,11 @@ static void nohz_balancer_kick(struct rq *rq) if (sds) { /* * If there is an imbalance between LLC domains (IOW we could - * increase the overall cache use), we need some less-loaded LLC - * domain to pull some load. Likewise, we may need to spread + * increase the overall cache utilization), we need a less-loaded LLC + * domain to pull some load from. Likewise, we may need to spread * load within the current LLC domain (e.g. packed SMT cores but * other CPUs are idle). We can't really know from here how busy - * the others are - so just get a nohz balance going if it looks + * the others are - so just get a NOHZ balance going if it looks * like this LLC domain has tasks we could move. */ nr_busy = atomic_read(&sds->nr_busy_cpus); |