[RFC PATCH v2 4/5] hugetlb: parallelize 2M hugetlb allocation and initialization

[Gang Li <gang.li@linux.dev>]

By distributing both the allocation and the initialization tasks across
multiple threads, the initialization of 2M hugetlb will be faster,
thereby improving the boot speed.

This patch can achieve 60% improvement in performance.

        test          no patch(ms)   patched(ms)   saved
 ------------------- -------------- ------------- --------
  256c2t(4 node) 2M           2624           956   63.57%
  128c1t(2 node) 2M           1788           684   61.74%

Signed-off-by: Gang Li <gang.li@linux.dev>
---
 mm/hugetlb.c | 71 ++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 52 insertions(+), 19 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8de1653fc4c4f..033e359fdb86b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -35,6 +35,7 @@
 #include <linux/delayacct.h>
 #include <linux/memory.h>
 #include <linux/mm_inline.h>
+#include <linux/padata.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
@@ -3502,6 +3503,37 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
 	}
 }
 
+static void __init hugetlb_alloc_node(unsigned long start, unsigned long end, void *arg)
+{
+	struct hstate *h = (struct hstate *)arg;
+	int i, num = end - start;
+	nodemask_t node_alloc_noretry;
+	unsigned long flags;
+
+	/* Bit mask controlling how hard we retry per-node allocations.*/
+	nodes_clear(node_alloc_noretry);
+
+	for (i = 0; i < num; ++i) {
+		struct folio *folio = alloc_pool_huge_folio(h, &node_states[N_MEMORY],
+						&node_alloc_noretry);
+		if (!folio)
+			break;
+		spin_lock_irqsave(&hugetlb_lock, flags);
+		__prep_account_new_huge_page(h, folio_nid(folio));
+		enqueue_hugetlb_folio(h, folio);
+		spin_unlock_irqrestore(&hugetlb_lock, flags);
+		cond_resched();
+	}
+}
+
+static void __init hugetlb_vmemmap_optimize_node(unsigned long start, unsigned long end, void *arg)
+{
+	struct hstate *h = (struct hstate *)arg;
+	int nid = start;
+
+	hugetlb_vmemmap_optimize_folios(h, &h->hugepage_freelists[nid]);
+}
+
 static unsigned long __init hugetlb_hstate_alloc_pages_gigantic(struct hstate *h)
 {
 	unsigned long i;
@@ -3521,26 +3553,27 @@ static unsigned long __init hugetlb_hstate_alloc_pages_gigantic(struct hstate *h
 
 static unsigned long __init hugetlb_hstate_alloc_pages_non_gigantic(struct hstate *h)
 {
-	unsigned long i;
-	struct folio *folio;
-	LIST_HEAD(folio_list);
-	nodemask_t node_alloc_noretry;
-
-	/* Bit mask controlling how hard we retry per-node allocations.*/
-	nodes_clear(node_alloc_noretry);
-
-	for (i = 0; i < h->max_huge_pages; ++i) {
-		folio = alloc_pool_huge_folio(h, &node_states[N_MEMORY],
-						&node_alloc_noretry);
-		if (!folio)
-			break;
-		list_add(&folio->lru, &folio_list);
-		cond_resched();
-	}
-
-	prep_and_add_allocated_folios(h, &folio_list);
+	struct padata_mt_job job = {
+		.fn_arg		= h,
+		.align		= 1,
+		.numa_aware	= true,
+	};
 
-	return i;
+	job.thread_fn	= hugetlb_alloc_node,
+	job.start	= 0,
+	job.size	= h->max_huge_pages,
+	job.min_chunk	= h->max_huge_pages / num_node_state(N_MEMORY) / 2,
+	job.max_threads	= num_node_state(N_MEMORY) * 2,
+	padata_do_multithreaded(&job);
+
+	job.thread_fn	= hugetlb_vmemmap_optimize_node,
+	job.start	= 0,
+	job.size	= num_node_state(N_MEMORY),
+	job.min_chunk	= 1,
+	job.max_threads	= num_node_state(N_MEMORY),
+	padata_do_multithreaded(&job);
+
+	return h->nr_huge_pages;
 }
 
 /*
-- 
2.30.2