When a group of tasks that access different nodes are scheduled on the
same node, they may encounter bandwidth bottlenecks and access latency.
Thus, numa_aware flag is introduced here, allowing tasks to be
distributed across different nodes to fully utilize the advantage of
multi-node systems.
Signed-off-by: Gang Li <gang.li@xxxxxxxxx>
Tested-by: David Rientjes <rientjes@xxxxxxxxxx>
---
include/linux/padata.h | 3 +++
kernel/padata.c | 14 ++++++++++++--
mm/mm_init.c | 1 +
3 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/include/linux/padata.h b/include/linux/padata.h
index 495b16b6b4d7..f79ccd50e7f4 100644
--- a/include/linux/padata.h
+++ b/include/linux/padata.h
@@ -137,6 +137,8 @@ struct padata_shell {
* appropriate for one worker thread to do at once.
* @max_threads: Max threads to use for the job, actual number may be less
* depending on task size and minimum chunk size.
+ * @numa_aware: Dispatch jobs to different nodes. If a node only has memory but
+ * no CPU, dispatch its jobs to a random CPU.
*/
struct padata_mt_job {
void (*thread_fn)(unsigned long start, unsigned long end, void *arg);
@@ -146,6 +148,7 @@ struct padata_mt_job {
unsigned long align;
unsigned long min_chunk;
int max_threads;
+ bool numa_aware;
};
/**
diff --git a/kernel/padata.c b/kernel/padata.c
index 179fb1518070..10eae3f59203 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -485,7 +485,8 @@ void __init padata_do_multithreaded(struct padata_mt_job *job)
struct padata_work my_work, *pw;
struct padata_mt_job_state ps;
LIST_HEAD(works);
- int nworks;
+ int nworks, nid;
+ static atomic_t last_used_nid = ATOMIC_INIT(0);
if (job->size == 0)
return;
@@ -517,7 +518,16 @@ void __init padata_do_multithreaded(struct padata_mt_job *job)
ps.chunk_size = roundup(ps.chunk_size, job->align);
list_for_each_entry(pw, &works, pw_list)
- queue_work(system_unbound_wq, &pw->pw_work);
+ if (job->numa_aware) {
+ int old_node = atomic_read(&last_used_nid);
+
+ do {
+ nid = next_node_in(old_node, node_states[N_CPU]);
+ } while (!atomic_try_cmpxchg(&last_used_nid, &old_node, nid));
+ queue_work_node(nid, system_unbound_wq, &pw->pw_work);
+ } else {
+ queue_work(system_unbound_wq, &pw->pw_work);
+ }
/* Use the current thread, which saves starting a workqueue worker. */
padata_work_init(&my_work, padata_mt_helper, &ps, PADATA_WORK_ONSTACK);
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 2c19f5515e36..549e76af8f82 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2231,6 +2231,7 @@ static int __init deferred_init_memmap(void *data)
.align = PAGES_PER_SECTION,
.min_chunk = PAGES_PER_SECTION,
.max_threads = max_threads,
+ .numa_aware = false,
};
padata_do_multithreaded(&job);
--
2.20.1
