Hi,
On Thu, Feb 22, 2024 at 10:04:17PM +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 <ligang.bdlg@xxxxxxxxxxxxx>
> Tested-by: David Rientjes <rientjes@xxxxxxxxxx>
> Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
> Reviewed-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> ---
> include/linux/padata.h | 2 ++
> kernel/padata.c | 14 ++++++++++++--
> mm/mm_init.c | 1 +
> 3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/padata.h b/include/linux/padata.h
> index 495b16b6b4d72..8f418711351bc 100644
> --- a/include/linux/padata.h
> +++ b/include/linux/padata.h
> @@ -137,6 +137,7 @@ 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: Distribute jobs to different nodes with CPU in a round robin fashion.
numa_interleave seems more descriptive.
> */
> struct padata_mt_job {
> void (*thread_fn)(unsigned long start, unsigned long end, void *arg);
> @@ -146,6 +147,7 @@ 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..e3f639ff16707 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 __initdata;
nit, move last_used_nid up so it's below load_balance_factor to keep
that nice tree shape
>
> 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));
There aren't concurrent NUMA-aware _do_multithreaded calls now, so an
atomic per work seems like an unnecessary expense for guarding against
possible uneven thread distribution in the future. Non-atomic access
instead?
> + 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 2c19f5515e36c..549e76af8f82a 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
>
