On 2024/1/12 01:50, Tim Chen wrote:
On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
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>
---
include/linux/padata.h | 3 +++
kernel/padata.c | 8 ++++++--
mm/mm_init.c | 1 +
3 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/linux/padata.h b/include/linux/padata.h
index 495b16b6b4d72..f79ccd50e7f40 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 179fb1518070c..1c2b3a337479e 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -485,7 +485,7 @@ 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 = 0;
If we always start from 0, we may be biased towards the low numbered node,
and not use high numbered nodes at all. Suggest you do
static nid = 0;
When we use `static`, if there are multiple parallel calls to
`padata_do_multithreaded`, it may result in an uneven distribution of
tasks for each padata_do_multithreaded.
We can make the following modifications to address this issue.
```
diff --git a/kernel/padata.c b/kernel/padata.c
index 1c2b3a337479e..925e48df6dd8d 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, nid = 0;
+ int nworks, nid;
+ static volatile int global_nid = 0;
if (job->size == 0)
return;
@@ -516,12 +517,15 @@ void __init padata_do_multithreaded(struct
padata_mt_job *job)
ps.chunk_size = max(ps.chunk_size, job->min_chunk);
ps.chunk_size = roundup(ps.chunk_size, job->align);
+ nid = global_nid;
list_for_each_entry(pw, &works, pw_list)
- if (job->numa_aware)
- queue_work_node((++nid % num_node_state(N_MEMORY)),
- system_unbound_wq, &pw->pw_work);
- else
+ if (job->numa_aware) {
+ queue_work_node(nid, system_unbound_wq,
&pw->pw_work);
+ nid = next_node(nid, node_states[N_CPU]);
+ } else
queue_work(system_unbound_wq, &pw->pw_work);
+ if (job->numa_aware)
+ global_nid = nid;
/* Use the current thread, which saves starting a workqueue
worker. */
padata_work_init(&my_work, padata_mt_helper, &ps,
PADATA_WORK_ONSTACK);
```
if (job->size == 0)
return;
@@ -517,7 +517,11 @@ 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)
+ queue_work_node((++nid % num_node_state(N_MEMORY)),
+ system_unbound_wq, &pw->pw_work);
I think we should use nid = next_node(nid, node_states[N_CPU]) instead of
++nid % num_node_state(N_MEMORY). You are picking the next node with CPU
to handle the job.
Tim
I agree.
