kernel/sched/fair.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+)
Optimize update_numa_stats() by leveraging pre-calculated node
statistics cached during the load balancing process. This reduces the
complexity of NUMA balancing overhead from O(CPUs_per_node) to O(1)
when statistics for the source node are fresh.
Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>
---
kernel/sched/fair.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e71302282671..070b61f65b6d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2094,6 +2094,17 @@ static inline int numa_idle_core(int idle_core, int cpu)
* borrows code and logic from update_sg_lb_stats but sharing a
* common implementation is impractical.
*/
+struct numa_stats_cache {
+ unsigned long load;
+ unsigned long runnable;
+ unsigned long util;
+ unsigned long nr_running;
+ unsigned long capacity;
+ unsigned long last_update;
+};
+
+static struct numa_stats_cache node_stats_cache[MAX_NUMNODES];
+
static void update_numa_stats(struct task_numa_env *env,
struct numa_stats *ns, int nid,
bool find_idle)
@@ -2104,6 +2115,24 @@ static void update_numa_stats(struct task_numa_env *env,
ns->idle_cpu = -1;
rcu_read_lock();
+ /*
+ * Algorithmic Optimization: Avoid O(N) scan by using cached stats.
+ * Only applicable for the source node where we don't need to find
+ * an idle CPU.
+ */
+ if (!find_idle && nid == env->src_nid) {
+ struct numa_stats_cache *cache = &node_stats_cache[nid];
+
+ if (time_before(jiffies, cache->last_update + msecs_to_jiffies(10))) {
+ ns->load = READ_ONCE(cache->load);
+ ns->runnable = READ_ONCE(cache->runnable);
+ ns->util = READ_ONCE(cache->util);
+ ns->nr_running = READ_ONCE(cache->nr_running);
+ ns->compute_capacity = READ_ONCE(cache->capacity);
+ goto skip_scan;
+ }
+ }
+
for_each_cpu(cpu, cpumask_of_node(nid)) {
struct rq *rq = cpu_rq(cpu);
@@ -2124,6 +2153,8 @@ static void update_numa_stats(struct task_numa_env *env,
idle_core = numa_idle_core(idle_core, cpu);
}
}
+
+skip_scan:
rcu_read_unlock();
ns->weight = cpumask_weight(cpumask_of_node(nid));
@@ -10488,6 +10519,19 @@ static inline void update_sg_lb_stats(struct lb_env *env,
if (sgs->group_type == group_overloaded)
sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
sgs->group_capacity;
+
+ /* Algorithmic Optimization: Cache node stats for O(1) NUMA lookups */
+ if (env->sd->flags & SD_NUMA) {
+ int nid = cpu_to_node(cpumask_first(sched_group_span(group)));
+ struct numa_stats_cache *cache = &node_stats_cache[nid];
+
+ WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
+ WRITE_ONCE(cache->load, sgs->group_load);
+ WRITE_ONCE(cache->util, sgs->group_util);
+ WRITE_ONCE(cache->runnable, sgs->group_runnable);
+ WRITE_ONCE(cache->capacity, sgs->group_capacity);
+ WRITE_ONCE(cache->last_update, jiffies);
+ }
}
/**
--
2.51.0Hello Qiliang,
On 1/26/2026 4:32 PM, Qiliang Yuan wrote:
> Optimize update_numa_stats() by leveraging pre-calculated node
> statistics cached during the load balancing process. This reduces the
> complexity of NUMA balancing overhead from O(CPUs_per_node) to O(1)
> when statistics for the source node are fresh.
>
> Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
> Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>
> ---
Missing a changelog and the performance numbers that justify this
change.
> kernel/sched/fair.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e71302282671..070b61f65b6d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2094,6 +2094,17 @@ static inline int numa_idle_core(int idle_core, int cpu)
> * borrows code and logic from update_sg_lb_stats but sharing a
> * common implementation is impractical.
> */
> +struct numa_stats_cache {
> + unsigned long load;
> + unsigned long runnable;
> + unsigned long util;
> + unsigned long nr_running;
> + unsigned long capacity;
> + unsigned long last_update;
> +};
> +
> +static struct numa_stats_cache node_stats_cache[MAX_NUMNODES];
MAX_NUMNODES is a very large value. Why do you need to have this
all up front and not dynamically allocate it during sched domain
build.
Speaking of sched domains, partitioning the system can make it
so that the NUMA domain is split across multiple partition which
makes these numbers partition specific. Tasks running in one
partition cannot use the cached values from another partition.
If there is really a noticeable benefit, I would suggest using
the previous method to cache it somewhere in the sched domain
hierarchy - but only if there is a noticeable benefit.
> +
> static void update_numa_stats(struct task_numa_env *env,
> struct numa_stats *ns, int nid,
> bool find_idle)
> @@ -2104,6 +2115,24 @@ static void update_numa_stats(struct task_numa_env *env,
> ns->idle_cpu = -1;
>
> rcu_read_lock();
> + /*
> + * Algorithmic Optimization: Avoid O(N) scan by using cached stats.
> + * Only applicable for the source node where we don't need to find
> + * an idle CPU.
> + */
> + if (!find_idle && nid == env->src_nid) {
> + struct numa_stats_cache *cache = &node_stats_cache[nid];
> +
> + if (time_before(jiffies, cache->last_update + msecs_to_jiffies(10))) {
> + ns->load = READ_ONCE(cache->load);
> + ns->runnable = READ_ONCE(cache->runnable);
> + ns->util = READ_ONCE(cache->util);
> + ns->nr_running = READ_ONCE(cache->nr_running);
> + ns->compute_capacity = READ_ONCE(cache->capacity);
So READ_ONCE()/WRITE_ONCE() doesn't solve the issue I was highlighting
in the last version. Say the following happens:
CPU0 CPU1
==== ====
update_numa_stats()
/* Working on current numa_stats_cache */
ns->load = READ_ONCE(cache->load);
ns->runnable = READ_ONCE(cache->runnable);
... interrupted update_sg_lb_stats()
... ... updates the entire numa_stats_cache
...
ns->util = READ_ONCE(cache->util); /* Sees new data. */
Can this cause an issue? If not, please highlight in the commit log why
it is not an issue. There can be cases where we see util > capacity,
util > runnable, etc. which might lead to incorrect calculations later
on.
> + goto skip_scan;
> + }
> + }
> +
> for_each_cpu(cpu, cpumask_of_node(nid)) {
> struct rq *rq = cpu_rq(cpu);
>
> @@ -2124,6 +2153,8 @@ static void update_numa_stats(struct task_numa_env *env,
> idle_core = numa_idle_core(idle_core, cpu);
> }
> }
> +
> +skip_scan:
> rcu_read_unlock();
>
> ns->weight = cpumask_weight(cpumask_of_node(nid));
> @@ -10488,6 +10519,19 @@ static inline void update_sg_lb_stats(struct lb_env *env,
> if (sgs->group_type == group_overloaded)
> sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
> sgs->group_capacity;
> +
> + /* Algorithmic Optimization: Cache node stats for O(1) NUMA lookups */
> + if (env->sd->flags & SD_NUMA) {
Also you'll need to think about partitions.
--
Thanks and Regards,
Prateek
Hi Qiliang,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/sched/core]
[also build test ERROR on linus/master v6.19-rc7 next-20260123]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Qiliang-Yuan/sched-fair-Cache-NUMA-node-statistics-to-avoid-O-N-scanning/20260126-190546
base: tip/sched/core
patch link: https://lore.kernel.org/r/20260126110250.1060512-1-realwujing%40gmail.com
patch subject: [PATCH v3] sched/fair: Cache NUMA node statistics to avoid O(N) scanning
config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20260127/202601270016.PIXAItvH-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260127/202601270016.PIXAItvH-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601270016.PIXAItvH-lkp@intel.com/
All errors (new ones prefixed by >>):
>> kernel/sched/fair.c:10524:37: error: use of undeclared identifier 'node_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:610:10: note: expanded from macro '__native_word'
610 | (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:610:39: note: expanded from macro '__native_word'
610 | (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:611:10: note: expanded from macro '__native_word'
611 | sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:611:38: note: expanded from macro '__native_word'
611 | sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:48: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:61:15: note: expanded from macro 'WRITE_ONCE'
61 | __WRITE_ONCE(x, val); \
| ^
include/asm-generic/rwonce.h:55:20: note: expanded from macro '__WRITE_ONCE'
55 | *(volatile typeof(x) *)&(x) = (val); \
| ^
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
>> kernel/sched/fair.c:10526:19: error: incomplete definition of type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ~~~~~^
include/asm-generic/rwonce.h:61:15: note: expanded from macro 'WRITE_ONCE'
61 | __WRITE_ONCE(x, val); \
| ^
include/asm-generic/rwonce.h:55:27: note: expanded from macro '__WRITE_ONCE'
55 | *(volatile typeof(x) *)&(x) = (val); \
| ^
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
kernel/sched/fair.c:10527:19: error: incomplete definition of type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:610:10: note: expanded from macro '__native_word'
610 | (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
kernel/sched/fair.c:10527:19: error: incomplete definition of type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:610:39: note: expanded from macro '__native_word'
610 | (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
kernel/sched/fair.c:10527:19: error: incomplete definition of type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:611:10: note: expanded from macro '__native_word'
611 | sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
| ^~~~~~~~~
include/linux/compiler_types.h:629:9: note: expanded from macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
kernel/sched/fair.c:10524:10: note: forward declaration of 'struct numa_stats_cache'
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^
kernel/sched/fair.c:10527:19: error: incomplete definition of type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ~~~~~^
include/asm-generic/rwonce.h:60:33: note: expanded from macro 'WRITE_ONCE'
60 | compiletime_assert_rwonce_type(x); \
| ^
include/asm-generic/rwonce.h:36:35: note: expanded from macro 'compiletime_assert_rwonce_type'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^
include/linux/compiler_types.h:611:38: note: expanded from macro '__native_word'
611 | sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
| ^
include/linux/compiler_types.h:649:22: note: expanded from macro 'compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~
include/linux/compiler_types.h:637:23: note: expanded from macro '_compiletime_assert'
637 | __compiletime_assert(condition, msg, prefix, suffix)
vim +/node_stats_cache +10524 kernel/sched/fair.c
10426
10427 /**
10428 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
10429 * @env: The load balancing environment.
10430 * @sds: Load-balancing data with statistics of the local group.
10431 * @group: sched_group whose statistics are to be updated.
10432 * @sgs: variable to hold the statistics for this group.
10433 * @sg_overloaded: sched_group is overloaded
10434 * @sg_overutilized: sched_group is overutilized
10435 */
10436 static inline void update_sg_lb_stats(struct lb_env *env,
10437 struct sd_lb_stats *sds,
10438 struct sched_group *group,
10439 struct sg_lb_stats *sgs,
10440 bool *sg_overloaded,
10441 bool *sg_overutilized)
10442 {
10443 int i, nr_running, local_group, sd_flags = env->sd->flags;
10444 bool balancing_at_rd = !env->sd->parent;
10445
10446 memset(sgs, 0, sizeof(*sgs));
10447
10448 local_group = group == sds->local;
10449
10450 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
10451 struct rq *rq = cpu_rq(i);
10452 unsigned long load = cpu_load(rq);
10453
10454 sgs->group_load += load;
10455 sgs->group_util += cpu_util_cfs(i);
10456 sgs->group_runnable += cpu_runnable(rq);
10457 sgs->sum_h_nr_running += rq->cfs.h_nr_runnable;
10458
10459 nr_running = rq->nr_running;
10460 sgs->sum_nr_running += nr_running;
10461
10462 if (cpu_overutilized(i))
10463 *sg_overutilized = 1;
10464
10465 /*
10466 * No need to call idle_cpu() if nr_running is not 0
10467 */
10468 if (!nr_running && idle_cpu(i)) {
10469 sgs->idle_cpus++;
10470 /* Idle cpu can't have misfit task */
10471 continue;
10472 }
10473
10474 /* Overload indicator is only updated at root domain */
10475 if (balancing_at_rd && nr_running > 1)
10476 *sg_overloaded = 1;
10477
10478 #ifdef CONFIG_NUMA_BALANCING
10479 /* Only fbq_classify_group() uses this to classify NUMA groups */
10480 if (sd_flags & SD_NUMA) {
10481 sgs->nr_numa_running += rq->nr_numa_running;
10482 sgs->nr_preferred_running += rq->nr_preferred_running;
10483 }
10484 #endif
10485 if (local_group)
10486 continue;
10487
10488 if (sd_flags & SD_ASYM_CPUCAPACITY) {
10489 /* Check for a misfit task on the cpu */
10490 if (sgs->group_misfit_task_load < rq->misfit_task_load) {
10491 sgs->group_misfit_task_load = rq->misfit_task_load;
10492 *sg_overloaded = 1;
10493 }
10494 } else if (env->idle && sched_reduced_capacity(rq, env->sd)) {
10495 /* Check for a task running on a CPU with reduced capacity */
10496 if (sgs->group_misfit_task_load < load)
10497 sgs->group_misfit_task_load = load;
10498 }
10499 }
10500
10501 sgs->group_capacity = group->sgc->capacity;
10502
10503 sgs->group_weight = group->group_weight;
10504
10505 /* Check if dst CPU is idle and preferred to this group */
10506 if (!local_group && env->idle && sgs->sum_h_nr_running &&
10507 sched_group_asym(env, sgs, group))
10508 sgs->group_asym_packing = 1;
10509
10510 /* Check for loaded SMT group to be balanced to dst CPU */
10511 if (!local_group && smt_balance(env, sgs, group))
10512 sgs->group_smt_balance = 1;
10513
10514 sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
10515
10516 /* Computing avg_load makes sense only when group is overloaded */
10517 if (sgs->group_type == group_overloaded)
10518 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
10519 sgs->group_capacity;
10520
10521 /* Algorithmic Optimization: Cache node stats for O(1) NUMA lookups */
10522 if (env->sd->flags & SD_NUMA) {
10523 int nid = cpu_to_node(cpumask_first(sched_group_span(group)));
10524 struct numa_stats_cache *cache = &node_stats_cache[nid];
10525
10526 WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
10527 WRITE_ONCE(cache->load, sgs->group_load);
10528 WRITE_ONCE(cache->util, sgs->group_util);
10529 WRITE_ONCE(cache->runnable, sgs->group_runnable);
10530 WRITE_ONCE(cache->capacity, sgs->group_capacity);
10531 WRITE_ONCE(cache->last_update, jiffies);
10532 }
10533 }
10534
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Qiliang,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/sched/core]
[also build test ERROR on linus/master v6.19-rc7 next-20260123]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Qiliang-Yuan/sched-fair-Cache-NUMA-node-statistics-to-avoid-O-N-scanning/20260126-190546
base: tip/sched/core
patch link: https://lore.kernel.org/r/20260126110250.1060512-1-realwujing%40gmail.com
patch subject: [PATCH v3] sched/fair: Cache NUMA node statistics to avoid O(N) scanning
config: nios2-allnoconfig (https://download.01.org/0day-ci/archive/20260126/202601262359.B2LmQ3KH-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260126/202601262359.B2LmQ3KH-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601262359.B2LmQ3KH-lkp@intel.com/
All errors (new ones prefixed by >>):
kernel/sched/fair.c: In function 'update_sg_lb_stats':
>> kernel/sched/fair.c:10524:51: error: 'node_stats_cache' undeclared (first use in this function); did you mean 'numa_stats_cache'?
10524 | struct numa_stats_cache *cache = &node_stats_cache[nid];
| ^~~~~~~~~~~~~~~~
| numa_stats_cache
kernel/sched/fair.c:10524:51: note: each undeclared identifier is reported only once for each function it appears in
In file included from <command-line>:
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
In file included from ./arch/nios2/include/generated/asm/rwonce.h:1,
from include/linux/compiler.h:380,
from include/linux/cleanup.h:5,
from include/linux/irqflags.h:17,
from include/asm-generic/cmpxchg.h:15,
from ./arch/nios2/include/generated/asm/cmpxchg.h:1,
from include/asm-generic/atomic.h:12,
from ./arch/nios2/include/generated/asm/atomic.h:1,
from include/linux/atomic.h:7,
from include/linux/cpumask.h:10,
from include/linux/energy_model.h:4,
from kernel/sched/fair.c:23:
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/asm-generic/rwonce.h:55:27: note: in definition of macro '__WRITE_ONCE'
55 | *(volatile typeof(x) *)&(x) = (val); \
| ^
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
>> kernel/sched/fair.c:10526:33: error: invalid use of undefined type 'struct numa_stats_cache'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~
include/asm-generic/rwonce.h:55:34: note: in definition of macro '__WRITE_ONCE'
55 | *(volatile typeof(x) *)&(x) = (val); \
| ^
kernel/sched/fair.c:10526:17: note: in expansion of macro 'WRITE_ONCE'
10526 | WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
| ^~~~~~~~~~
In file included from <command-line>:
kernel/sched/fair.c:10527:33: error: invalid use of undefined type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10527:17: note: in expansion of macro 'WRITE_ONCE'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~~~~~~~~~
kernel/sched/fair.c:10527:33: error: invalid use of undefined type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10527:17: note: in expansion of macro 'WRITE_ONCE'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~~~~~~~~~
kernel/sched/fair.c:10527:33: error: invalid use of undefined type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10527:17: note: in expansion of macro 'WRITE_ONCE'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~~~~~~~~~
kernel/sched/fair.c:10527:33: error: invalid use of undefined type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
649 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:9: note: in expansion of macro 'compiletime_assert'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:36:28: note: in expansion of macro '__native_word'
36 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~
include/asm-generic/rwonce.h:60:9: note: in expansion of macro 'compiletime_assert_rwonce_type'
60 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/sched/fair.c:10527:17: note: in expansion of macro 'WRITE_ONCE'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~~~~~~~~~
kernel/sched/fair.c:10527:33: error: invalid use of undefined type 'struct numa_stats_cache'
10527 | WRITE_ONCE(cache->load, sgs->group_load);
| ^~
include/linux/compiler_types.h:629:23: note: in definition of macro '__compiletime_assert'
629 | if (!(condition)) \
| ^~~~~~~~~
include/linux/compiler_types.h:649:9: note: in expansion of macro '_compiletime_assert'
vim +10524 kernel/sched/fair.c
10426
10427 /**
10428 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
10429 * @env: The load balancing environment.
10430 * @sds: Load-balancing data with statistics of the local group.
10431 * @group: sched_group whose statistics are to be updated.
10432 * @sgs: variable to hold the statistics for this group.
10433 * @sg_overloaded: sched_group is overloaded
10434 * @sg_overutilized: sched_group is overutilized
10435 */
10436 static inline void update_sg_lb_stats(struct lb_env *env,
10437 struct sd_lb_stats *sds,
10438 struct sched_group *group,
10439 struct sg_lb_stats *sgs,
10440 bool *sg_overloaded,
10441 bool *sg_overutilized)
10442 {
10443 int i, nr_running, local_group, sd_flags = env->sd->flags;
10444 bool balancing_at_rd = !env->sd->parent;
10445
10446 memset(sgs, 0, sizeof(*sgs));
10447
10448 local_group = group == sds->local;
10449
10450 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
10451 struct rq *rq = cpu_rq(i);
10452 unsigned long load = cpu_load(rq);
10453
10454 sgs->group_load += load;
10455 sgs->group_util += cpu_util_cfs(i);
10456 sgs->group_runnable += cpu_runnable(rq);
10457 sgs->sum_h_nr_running += rq->cfs.h_nr_runnable;
10458
10459 nr_running = rq->nr_running;
10460 sgs->sum_nr_running += nr_running;
10461
10462 if (cpu_overutilized(i))
10463 *sg_overutilized = 1;
10464
10465 /*
10466 * No need to call idle_cpu() if nr_running is not 0
10467 */
10468 if (!nr_running && idle_cpu(i)) {
10469 sgs->idle_cpus++;
10470 /* Idle cpu can't have misfit task */
10471 continue;
10472 }
10473
10474 /* Overload indicator is only updated at root domain */
10475 if (balancing_at_rd && nr_running > 1)
10476 *sg_overloaded = 1;
10477
10478 #ifdef CONFIG_NUMA_BALANCING
10479 /* Only fbq_classify_group() uses this to classify NUMA groups */
10480 if (sd_flags & SD_NUMA) {
10481 sgs->nr_numa_running += rq->nr_numa_running;
10482 sgs->nr_preferred_running += rq->nr_preferred_running;
10483 }
10484 #endif
10485 if (local_group)
10486 continue;
10487
10488 if (sd_flags & SD_ASYM_CPUCAPACITY) {
10489 /* Check for a misfit task on the cpu */
10490 if (sgs->group_misfit_task_load < rq->misfit_task_load) {
10491 sgs->group_misfit_task_load = rq->misfit_task_load;
10492 *sg_overloaded = 1;
10493 }
10494 } else if (env->idle && sched_reduced_capacity(rq, env->sd)) {
10495 /* Check for a task running on a CPU with reduced capacity */
10496 if (sgs->group_misfit_task_load < load)
10497 sgs->group_misfit_task_load = load;
10498 }
10499 }
10500
10501 sgs->group_capacity = group->sgc->capacity;
10502
10503 sgs->group_weight = group->group_weight;
10504
10505 /* Check if dst CPU is idle and preferred to this group */
10506 if (!local_group && env->idle && sgs->sum_h_nr_running &&
10507 sched_group_asym(env, sgs, group))
10508 sgs->group_asym_packing = 1;
10509
10510 /* Check for loaded SMT group to be balanced to dst CPU */
10511 if (!local_group && smt_balance(env, sgs, group))
10512 sgs->group_smt_balance = 1;
10513
10514 sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
10515
10516 /* Computing avg_load makes sense only when group is overloaded */
10517 if (sgs->group_type == group_overloaded)
10518 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
10519 sgs->group_capacity;
10520
10521 /* Algorithmic Optimization: Cache node stats for O(1) NUMA lookups */
10522 if (env->sd->flags & SD_NUMA) {
10523 int nid = cpu_to_node(cpumask_first(sched_group_span(group)));
10524 struct numa_stats_cache *cache = &node_stats_cache[nid];
10525
10526 WRITE_ONCE(cache->nr_running, sgs->sum_h_nr_running);
10527 WRITE_ONCE(cache->load, sgs->group_load);
10528 WRITE_ONCE(cache->util, sgs->group_util);
10529 WRITE_ONCE(cache->runnable, sgs->group_runnable);
10530 WRITE_ONCE(cache->capacity, sgs->group_capacity);
10531 WRITE_ONCE(cache->last_update, jiffies);
10532 }
10533 }
10534
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
© 2016 - 2026 Red Hat, Inc.