[PATCH v3 0/7] hugetlb: parallelize hugetlb page init on boot

[PATCH v3 0/7] hugetlb: parallelize hugetlb page init on boot

[Gang Li]

Hi all, hugetlb init parallelization has now been updated to v3.

This series is tested on next-20240102 and can not be applied to v6.7-rc8.

Update Summary:
- Select CONFIG_PADATA as we use padata_do_multithreaded
- Fix a race condition in h->next_nid_to_alloc
- Fix local variable initialization issues
- Remove RFC tag

Thanks to the testing by David Rientjes, we now know that this patch reduce
hugetlb 1G initialization time from 77s to 18.3s on a 12T machine[4].

# Introduction
Hugetlb initialization during boot takes up a considerable amount of time.
For instance, on a 2TB system, initializing 1,800 1GB huge pages takes 1-2
seconds out of 10 seconds. Initializing 11,776 1GB pages on a 12TB Intel
host takes more than 1 minute[1]. This is a noteworthy figure.

Inspired by [2] and [3], hugetlb initialization can also be accelerated
through parallelization. Kernel already has infrastructure like
padata_do_multithreaded, this patch uses it to achieve effective results
by minimal modifications.

[1] https://lore.kernel.org/all/783f8bac-55b8-5b95-eb6a-11a583675000@google.com/
[2] https://lore.kernel.org/all/20200527173608.2885243-1-daniel.m.jordan@oracle.com/
[3] https://lore.kernel.org/all/20230906112605.2286994-1-usama.arif@bytedance.com/
[4] https://lore.kernel.org/all/76becfc1-e609-e3e8-2966-4053143170b6@google.com/

# Test result
        test          no patch(ms)   patched(ms)   saved   
 ------------------- -------------- ------------- -------- 
  256c2t(4 node) 1G           4745          2024   57.34%
  128c1t(2 node) 1G           3358          1712   49.02%
      12t        1G          77000         18300   76.23%

  256c2t(4 node) 2M           3336          1051   68.52%
  128c1t(2 node) 2M           1943           716   63.15%

# Change log
Changes in v3:
- Select CONFIG_PADATA as we use padata_do_multithreaded
- Fix a race condition in h->next_nid_to_alloc
- Fix local variable initialization issues
- Remove RFC tag

Changes in v2:
- https://lore.kernel.org/all/20231208025240.4744-1-gang.li@linux.dev/
- Reduce complexity with `padata_do_multithreaded`
- Support 1G hugetlb

v1:
- https://lore.kernel.org/all/20231123133036.68540-1-gang.li@linux.dev/
- parallelize 2M hugetlb initialization with workqueue

Gang Li (7):
  hugetlb: code clean for hugetlb_hstate_alloc_pages
  hugetlb: split hugetlb_hstate_alloc_pages
  padata: dispatch works on different nodes
  hugetlb: pass *next_nid_to_alloc directly to
    for_each_node_mask_to_alloc
  hugetlb: have CONFIG_HUGETLBFS select CONFIG_PADATA
  hugetlb: parallelize 2M hugetlb allocation and initialization
  hugetlb: parallelize 1G hugetlb initialization

 fs/Kconfig              |   1 +
 include/linux/hugetlb.h |   2 +-
 include/linux/padata.h  |   3 +
 kernel/padata.c         |   8 +-
 mm/hugetlb.c            | 224 +++++++++++++++++++++++++++-------------
 mm/mm_init.c            |   1 +
 6 files changed, 163 insertions(+), 76 deletions(-)

-- 
2.20.1

[PATCH v3 1/7] hugetlb: code clean for hugetlb_hstate_alloc_pages

[Gang Li]

The readability of `hugetlb_hstate_alloc_pages` is poor. By cleaning the
code, its readability can be improved, facilitating future modifications.

This patch extracts two functions to reduce the complexity of
`hugetlb_hstate_alloc_pages` and has no functional changes.

- hugetlb_hstate_alloc_pages_node_specific() to handle iterates through
  each online node and performs allocation if necessary.
- hugetlb_hstate_alloc_pages_report() report error during allocation.
  And the value of h->max_huge_pages is updated accordingly.

Signed-off-by: Gang Li <gang.li@linux.dev>
---
 mm/hugetlb.c | 46 +++++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ed1581b670d42..2606135ec55e6 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3482,6 +3482,33 @@ static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
 	h->max_huge_pages_node[nid] = i;
 }
 
+static bool __init hugetlb_hstate_alloc_pages_node_specific(struct hstate *h)
+{
+	int i;
+	bool node_specific_alloc = false;
+
+	for_each_online_node(i) {
+		if (h->max_huge_pages_node[i] > 0) {
+			hugetlb_hstate_alloc_pages_onenode(h, i);
+			node_specific_alloc = true;
+		}
+	}
+
+	return node_specific_alloc;
+}
+
+static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, struct hstate *h)
+{
+	if (allocated < h->max_huge_pages) {
+		char buf[32];
+
+		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
+		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
+			h->max_huge_pages, buf, allocated);
+		h->max_huge_pages = allocated;
+	}
+}
+
 /*
  * NOTE: this routine is called in different contexts for gigantic and
  * non-gigantic pages.
@@ -3499,7 +3526,6 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 	struct folio *folio;
 	LIST_HEAD(folio_list);
 	nodemask_t *node_alloc_noretry;
-	bool node_specific_alloc = false;
 
 	/* skip gigantic hugepages allocation if hugetlb_cma enabled */
 	if (hstate_is_gigantic(h) && hugetlb_cma_size) {
@@ -3508,14 +3534,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 	}
 
 	/* do node specific alloc */
-	for_each_online_node(i) {
-		if (h->max_huge_pages_node[i] > 0) {
-			hugetlb_hstate_alloc_pages_onenode(h, i);
-			node_specific_alloc = true;
-		}
-	}
-
-	if (node_specific_alloc)
+	if (hugetlb_hstate_alloc_pages_node_specific(h))
 		return;
 
 	/* below will do all node balanced alloc */
@@ -3558,14 +3577,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 	/* list will be empty if hstate_is_gigantic */
 	prep_and_add_allocated_folios(h, &folio_list);
 
-	if (i < h->max_huge_pages) {
-		char buf[32];
-
-		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
-		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
-			h->max_huge_pages, buf, i);
-		h->max_huge_pages = i;
-	}
+	hugetlb_hstate_alloc_pages_report(i, h);
 	kfree(node_alloc_noretry);
 }
 
-- 
2.20.1

[PATCH v3 2/7] hugetlb: split hugetlb_hstate_alloc_pages

[Gang Li]

1G and 2M huge pages have different allocation and initialization logic,
which leads to subtle differences in parallelization. Therefore, it is
appropriate to split hugetlb_hstate_alloc_pages into gigantic and
non-gigantic.

This patch has no functional changes.

Signed-off-by: Gang Li <gang.li@linux.dev>
---
 mm/hugetlb.c | 86 +++++++++++++++++++++++++++-------------------------
 1 file changed, 45 insertions(+), 41 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2606135ec55e6..92448e747991d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3509,6 +3509,47 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
 	}
 }
 
+static unsigned long __init hugetlb_hstate_alloc_pages_gigantic(struct hstate *h)
+{
+	unsigned long i;
+
+	for (i = 0; i < h->max_huge_pages; ++i) {
+		/*
+		 * gigantic pages not added to list as they are not
+		 * added to pools now.
+		 */
+		if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
+			break;
+		cond_resched();
+	}
+
+	return i;
+}
+
+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);
+
+	return i;
+}
+
 /*
  * NOTE: this routine is called in different contexts for gigantic and
  * non-gigantic pages.
@@ -3522,10 +3563,7 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
  */
 static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 {
-	unsigned long i;
-	struct folio *folio;
-	LIST_HEAD(folio_list);
-	nodemask_t *node_alloc_noretry;
+	unsigned long allocated;
 
 	/* skip gigantic hugepages allocation if hugetlb_cma enabled */
 	if (hstate_is_gigantic(h) && hugetlb_cma_size) {
@@ -3539,46 +3577,12 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 
 	/* below will do all node balanced alloc */
 	if (!hstate_is_gigantic(h)) {
-		/*
-		 * Bit mask controlling how hard we retry per-node allocations.
-		 * Ignore errors as lower level routines can deal with
-		 * node_alloc_noretry == NULL.  If this kmalloc fails at boot
-		 * time, we are likely in bigger trouble.
-		 */
-		node_alloc_noretry = kmalloc(sizeof(*node_alloc_noretry),
-						GFP_KERNEL);
+		allocated = hugetlb_hstate_alloc_pages_non_gigantic(h);
 	} else {
-		/* allocations done at boot time */
-		node_alloc_noretry = NULL;
-	}
-
-	/* bit mask controlling how hard we retry per-node allocations */
-	if (node_alloc_noretry)
-		nodes_clear(*node_alloc_noretry);
-
-	for (i = 0; i < h->max_huge_pages; ++i) {
-		if (hstate_is_gigantic(h)) {
-			/*
-			 * gigantic pages not added to list as they are not
-			 * added to pools now.
-			 */
-			if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
-				break;
-		} else {
-			folio = alloc_pool_huge_folio(h, &node_states[N_MEMORY],
-							node_alloc_noretry);
-			if (!folio)
-				break;
-			list_add(&folio->lru, &folio_list);
-		}
-		cond_resched();
+		allocated = hugetlb_hstate_alloc_pages_gigantic(h);
 	}
 
-	/* list will be empty if hstate_is_gigantic */
-	prep_and_add_allocated_folios(h, &folio_list);
-
-	hugetlb_hstate_alloc_pages_report(i, h);
-	kfree(node_alloc_noretry);
+	hugetlb_hstate_alloc_pages_report(allocated, h);
 }
 
 static void __init hugetlb_init_hstates(void)
-- 
2.20.1

[PATCH v3 3/7] padata: dispatch works on different nodes

[Gang Li]

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@linux.dev>
---
 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 (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);
+		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 89dc29f1e6c6f..59fcffddf65a3 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2225,6 +2225,7 @@ 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

[PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to_alloc

[Gang Li]

The parallelization of hugetlb allocation leads to errors when sharing
h->next_nid_to_alloc across different threads. To address this, it's
necessary to assign a separate next_nid_to_alloc for each thread.

Consequently, the hstate_next_node_to_alloc and for_each_node_mask_to_alloc
have been modified to directly accept a *next_nid_to_alloc parameter,
ensuring thread-specific allocation and avoiding concurrent access issues.

Signed-off-by: Gang Li <gang.li@linux.dev>
---
This patch seems not elegant, but I can't come up with anything better.
Any suggestions will be highly appreciated!
---
 mm/hugetlb.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 92448e747991d..a71bc1622b53b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1464,15 +1464,15 @@ static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
  * next node from which to allocate, handling wrap at end of node
  * mask.
  */
-static int hstate_next_node_to_alloc(struct hstate *h,
+static int hstate_next_node_to_alloc(int *next_nid_to_alloc,
 					nodemask_t *nodes_allowed)
 {
 	int nid;
 
 	VM_BUG_ON(!nodes_allowed);
 
-	nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
-	h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
+	nid = get_valid_node_allowed(*next_nid_to_alloc, nodes_allowed);
+	*next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
 
 	return nid;
 }
@@ -1495,10 +1495,10 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
 	return nid;
 }
 
-#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask)		\
+#define for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, mask)		\
 	for (nr_nodes = nodes_weight(*mask);				\
 		nr_nodes > 0 &&						\
-		((node = hstate_next_node_to_alloc(hs, mask)) || 1);	\
+		((node = hstate_next_node_to_alloc(next_nid_to_alloc, mask)) || 1);	\
 		nr_nodes--)
 
 #define for_each_node_mask_to_free(hs, nr_nodes, node, mask)		\
@@ -2350,12 +2350,13 @@ static void prep_and_add_allocated_folios(struct hstate *h,
  */
 static struct folio *alloc_pool_huge_folio(struct hstate *h,
 					nodemask_t *nodes_allowed,
-					nodemask_t *node_alloc_noretry)
+					nodemask_t *node_alloc_noretry,
+					int *next_nid_to_alloc)
 {
 	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
 	int nr_nodes, node;
 
-	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
+	for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
 		struct folio *folio;
 
 		folio = only_alloc_fresh_hugetlb_folio(h, gfp_mask, node,
@@ -3310,7 +3311,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid)
 		goto found;
 	}
 	/* allocate from next node when distributing huge pages */
-	for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
+	for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
 		m = memblock_alloc_try_nid_raw(
 				huge_page_size(h), huge_page_size(h),
 				0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
@@ -3684,7 +3685,7 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
 	VM_BUG_ON(delta != -1 && delta != 1);
 
 	if (delta < 0) {
-		for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
+		for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
 			if (h->surplus_huge_pages_node[node])
 				goto found;
 		}
@@ -3799,7 +3800,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 		cond_resched();
 
 		folio = alloc_pool_huge_folio(h, nodes_allowed,
-						node_alloc_noretry);
+						node_alloc_noretry,
+						&h->next_nid_to_alloc);
 		if (!folio) {
 			prep_and_add_allocated_folios(h, &page_list);
 			spin_lock_irq(&hugetlb_lock);
-- 
2.20.1

[PATCH v3 5/7] hugetlb: have CONFIG_HUGETLBFS select CONFIG_PADATA

[Gang Li]

Now hugetlb uses padata_do_multithreaded for parallel initialization,
so select CONFIG_PADATA.

Signed-off-by: Gang Li <gang.li@linux.dev>
---
 fs/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/Kconfig b/fs/Kconfig
index 89fdbefd1075f..a57d6e6c41e6f 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -262,6 +262,7 @@ menuconfig HUGETLBFS
 	depends on X86 || SPARC64 || ARCH_SUPPORTS_HUGETLBFS || BROKEN
 	depends on (SYSFS || SYSCTL)
 	select MEMFD_CREATE
+	select PADATA
 	help
 	  hugetlbfs is a filesystem backing for HugeTLB pages, based on
 	  ramfs. For architectures that support it, say Y here and read
-- 
2.20.1

[PATCH v3 6/7] hugetlb: parallelize 2M hugetlb allocation and initialization

[Gang Li]

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.

Here are some test results:
        test          no patch(ms)   patched(ms)   saved
 ------------------- -------------- ------------- --------
  256c2t(4 node) 2M           3336          1051   68.52%
  128c1t(2 node) 2M           1943           716   63.15%

Signed-off-by: Gang Li <gang.li@linux.dev>
---
 mm/hugetlb.c | 72 ++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 53 insertions(+), 19 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a71bc1622b53b..d1629df5f399f 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>
@@ -3510,6 +3511,38 @@ 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;
+	int next_nid_to_alloc = 0;
+
+	/* 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, &next_nid_to_alloc);
+		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;
@@ -3529,26 +3562,27 @@ 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;
 }
 
 /*
-- 
2.20.1

[PATCH v3 7/7] hugetlb: parallelize 1G hugetlb initialization

[Gang Li]

Optimizing the initialization speed of 1G huge pages through
parallelization.

1G hugetlbs are allocated from bootmem, a process that is already
very fast and does not currently require optimization. Therefore,
we focus on parallelizing only the initialization phase in
`gather_bootmem_prealloc`.

Here are some test results:
        test          no patch(ms)   patched(ms)   saved
 ------------------- -------------- ------------- --------
  256c2t(4 node) 1G           4745          2024   57.34%
  128c1t(2 node) 1G           3358          1712   49.02%
      12t        1G          77000         18300   76.23%

Signed-off-by: Gang Li <gang.li@linux.dev>
---
 include/linux/hugetlb.h |  2 +-
 mm/hugetlb.c            | 40 +++++++++++++++++++++++++++++++++-------
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index c1ee640d87b11..77b30a8c6076b 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -178,7 +178,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
 struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage);
 
 extern int sysctl_hugetlb_shm_group;
-extern struct list_head huge_boot_pages;
+extern struct list_head huge_boot_pages[MAX_NUMNODES];
 
 /* arch callbacks */
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d1629df5f399f..e5a55707f8814 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -69,7 +69,7 @@ static bool hugetlb_cma_folio(struct folio *folio, unsigned int order)
 #endif
 static unsigned long hugetlb_cma_size __initdata;
 
-__initdata LIST_HEAD(huge_boot_pages);
+__initdata struct list_head huge_boot_pages[MAX_NUMNODES];
 
 /* for command line parsing */
 static struct hstate * __initdata parsed_hstate;
@@ -3339,7 +3339,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid)
 		huge_page_size(h) - PAGE_SIZE);
 	/* Put them into a private list first because mem_map is not up yet */
 	INIT_LIST_HEAD(&m->list);
-	list_add(&m->list, &huge_boot_pages);
+	list_add(&m->list, &huge_boot_pages[node]);
 	m->hstate = h;
 	return 1;
 }
@@ -3390,8 +3390,6 @@ static void __init prep_and_add_bootmem_folios(struct hstate *h,
 	/* Send list for bulk vmemmap optimization processing */
 	hugetlb_vmemmap_optimize_folios(h, folio_list);
 
-	/* Add all new pool pages to free lists in one lock cycle */
-	spin_lock_irqsave(&hugetlb_lock, flags);
 	list_for_each_entry_safe(folio, tmp_f, folio_list, lru) {
 		if (!folio_test_hugetlb_vmemmap_optimized(folio)) {
 			/*
@@ -3404,23 +3402,27 @@ static void __init prep_and_add_bootmem_folios(struct hstate *h,
 					HUGETLB_VMEMMAP_RESERVE_PAGES,
 					pages_per_huge_page(h));
 		}
+		/* Subdivide locks to achieve better parallel performance */
+		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);
 	}
-	spin_unlock_irqrestore(&hugetlb_lock, flags);
 }
 
 /*
  * Put bootmem huge pages into the standard lists after mem_map is up.
  * Note: This only applies to gigantic (order > MAX_PAGE_ORDER) pages.
  */
-static void __init gather_bootmem_prealloc(void)
+static void __init __gather_bootmem_prealloc(unsigned long start, unsigned long end, void *arg)
+
 {
+	int nid = start;
 	LIST_HEAD(folio_list);
 	struct huge_bootmem_page *m;
 	struct hstate *h = NULL, *prev_h = NULL;
 
-	list_for_each_entry(m, &huge_boot_pages, list) {
+	list_for_each_entry(m, &huge_boot_pages[nid], list) {
 		struct page *page = virt_to_page(m);
 		struct folio *folio = (void *)page;
 
@@ -3453,6 +3455,22 @@ static void __init gather_bootmem_prealloc(void)
 	prep_and_add_bootmem_folios(h, &folio_list);
 }
 
+static void __init gather_bootmem_prealloc(void)
+{
+	struct padata_mt_job job = {
+		.thread_fn	= __gather_bootmem_prealloc,
+		.fn_arg		= NULL,
+		.start		= 0,
+		.size		= num_node_state(N_MEMORY),
+		.align		= 1,
+		.min_chunk	= 1,
+		.max_threads	= num_node_state(N_MEMORY),
+		.numa_aware	= true,
+	};
+
+	padata_do_multithreaded(&job);
+}
+
 static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
 {
 	unsigned long i;
@@ -3606,6 +3624,14 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 		return;
 	}
 
+	/* hugetlb_hstate_alloc_pages will be called many times, init huge_boot_pages once*/
+	if (huge_boot_pages[0].next == NULL) {
+		int i = 0;
+
+		for (i = 0; i < MAX_NUMNODES; i++)
+			INIT_LIST_HEAD(&huge_boot_pages[i]);
+	}
+
 	/* do node specific alloc */
 	if (hugetlb_hstate_alloc_pages_node_specific(h))
 		return;
-- 
2.20.1

Re: [PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to_alloc

[David Rientjes]

On Tue, 2 Jan 2024, Gang Li wrote:

> The parallelization of hugetlb allocation leads to errors when sharing
> h->next_nid_to_alloc across different threads. To address this, it's
> necessary to assign a separate next_nid_to_alloc for each thread.
> 
> Consequently, the hstate_next_node_to_alloc and for_each_node_mask_to_alloc
> have been modified to directly accept a *next_nid_to_alloc parameter,
> ensuring thread-specific allocation and avoiding concurrent access issues.
> 
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
> This patch seems not elegant, but I can't come up with anything better.
> Any suggestions will be highly appreciated!

Same error as v2:

mm/hugetlb.c:3315:53: warning: variable 'node' is used uninitialized whenever '&&' condition is false [-Wsometimes-uninitialized]
        for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/hugetlb.c:1501:3: note: expanded from macro 'for_each_node_mask_to_alloc'
                nr_nodes > 0 &&                                         \
                ^~~~~~~~~~~~
mm/hugetlb.c:3342:38: note: uninitialized use occurs here
        list_add(&m->list, &huge_boot_pages[node]);
                                            ^~~~
mm/hugetlb.c:3315:53: note: remove the '&&' if its condition is always true
        for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
                                                           ^
mm/hugetlb.c:3310:7: warning: variable 'node' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
                if (!m)
                    ^~
mm/hugetlb.c:3342:38: note: uninitialized use occurs here
        list_add(&m->list, &huge_boot_pages[node]);
                                            ^~~~
mm/hugetlb.c:3310:3: note: remove the 'if' if its condition is always true
                if (!m)
                ^~~~~~~
mm/hugetlb.c:3304:20: note: initialize the variable 'node' to silence this warning
        int nr_nodes, node;
                          ^
                           = 0
2 warnings generated.

> ---
>  mm/hugetlb.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 92448e747991d..a71bc1622b53b 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1464,15 +1464,15 @@ static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
>   * next node from which to allocate, handling wrap at end of node
>   * mask.
>   */
> -static int hstate_next_node_to_alloc(struct hstate *h,
> +static int hstate_next_node_to_alloc(int *next_nid_to_alloc,
>  					nodemask_t *nodes_allowed)
>  {
>  	int nid;
>  
>  	VM_BUG_ON(!nodes_allowed);
>  
> -	nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
> -	h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
> +	nid = get_valid_node_allowed(*next_nid_to_alloc, nodes_allowed);
> +	*next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
>  
>  	return nid;
>  }
> @@ -1495,10 +1495,10 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
>  	return nid;
>  }
>  
> -#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask)		\
> +#define for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, mask)		\
>  	for (nr_nodes = nodes_weight(*mask);				\
>  		nr_nodes > 0 &&						\
> -		((node = hstate_next_node_to_alloc(hs, mask)) || 1);	\
> +		((node = hstate_next_node_to_alloc(next_nid_to_alloc, mask)) || 1);	\
>  		nr_nodes--)
>  
>  #define for_each_node_mask_to_free(hs, nr_nodes, node, mask)		\
> @@ -2350,12 +2350,13 @@ static void prep_and_add_allocated_folios(struct hstate *h,
>   */
>  static struct folio *alloc_pool_huge_folio(struct hstate *h,
>  					nodemask_t *nodes_allowed,
> -					nodemask_t *node_alloc_noretry)
> +					nodemask_t *node_alloc_noretry,
> +					int *next_nid_to_alloc)
>  {
>  	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
>  	int nr_nodes, node;
>  
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +	for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
>  		struct folio *folio;
>  
>  		folio = only_alloc_fresh_hugetlb_folio(h, gfp_mask, node,
> @@ -3310,7 +3311,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid)
>  		goto found;
>  	}
>  	/* allocate from next node when distributing huge pages */
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> +	for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
>  		m = memblock_alloc_try_nid_raw(
>  				huge_page_size(h), huge_page_size(h),
>  				0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
> @@ -3684,7 +3685,7 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
>  	VM_BUG_ON(delta != -1 && delta != 1);
>  
>  	if (delta < 0) {
> -		for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +		for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
>  			if (h->surplus_huge_pages_node[node])
>  				goto found;
>  		}
> @@ -3799,7 +3800,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
>  		cond_resched();
>  
>  		folio = alloc_pool_huge_folio(h, nodes_allowed,
> -						node_alloc_noretry);
> +						node_alloc_noretry,
> +						&h->next_nid_to_alloc);
>  		if (!folio) {
>  			prep_and_add_allocated_folios(h, &page_list);
>  			spin_lock_irq(&hugetlb_lock);
> -- 
> 2.20.1
> 
> 

Re: [PATCH v3 0/7] hugetlb: parallelize hugetlb page init on boot

[David Rientjes]

On Tue, 2 Jan 2024, Gang Li wrote:

> Hi all, hugetlb init parallelization has now been updated to v3.
> 
> This series is tested on next-20240102 and can not be applied to v6.7-rc8.
> 
> Update Summary:
> - Select CONFIG_PADATA as we use padata_do_multithreaded
> - Fix a race condition in h->next_nid_to_alloc
> - Fix local variable initialization issues
> - Remove RFC tag
> 
> Thanks to the testing by David Rientjes, we now know that this patch reduce
> hugetlb 1G initialization time from 77s to 18.3s on a 12T machine[4].
> 
> # Introduction
> Hugetlb initialization during boot takes up a considerable amount of time.
> For instance, on a 2TB system, initializing 1,800 1GB huge pages takes 1-2
> seconds out of 10 seconds. Initializing 11,776 1GB pages on a 12TB Intel
> host takes more than 1 minute[1]. This is a noteworthy figure.
> 
> Inspired by [2] and [3], hugetlb initialization can also be accelerated
> through parallelization. Kernel already has infrastructure like
> padata_do_multithreaded, this patch uses it to achieve effective results
> by minimal modifications.
> 
> [1] https://lore.kernel.org/all/783f8bac-55b8-5b95-eb6a-11a583675000@google.com/
> [2] https://lore.kernel.org/all/20200527173608.2885243-1-daniel.m.jordan@oracle.com/
> [3] https://lore.kernel.org/all/20230906112605.2286994-1-usama.arif@bytedance.com/
> [4] https://lore.kernel.org/all/76becfc1-e609-e3e8-2966-4053143170b6@google.com/
> 
> # Test result
>         test          no patch(ms)   patched(ms)   saved   
>  ------------------- -------------- ------------- -------- 
>   256c2t(4 node) 1G           4745          2024   57.34%
>   128c1t(2 node) 1G           3358          1712   49.02%
>       12t        1G          77000         18300   76.23%
> 
>   256c2t(4 node) 2M           3336          1051   68.52%
>   128c1t(2 node) 2M           1943           716   63.15%
> 

I tested 1GB hugetlb on a smaller AMD host with the following:

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3301,7 +3301,7 @@ int alloc_bootmem_huge_page(struct hstate *h, int nid)
 int __alloc_bootmem_huge_page(struct hstate *h, int nid)
 {
        struct huge_bootmem_page *m = NULL; /* initialize for clang */
-       int nr_nodes, node;
+       int nr_nodes, node = nid;
 
        /* do node specific alloc */
        if (nid != NUMA_NO_NODE) {

After the build error is fixed, feel free to add:

	Tested-by: David Rientjes <rientjes@google.com>

to each patch.  I think Andrew will probably take a build fix up as a
delta on top of patch 4 rather than sending a whole new series unless
there is other feedback that you receive.

Re: [PATCH v3 0/7] hugetlb: parallelize hugetlb page init on boot

[Gang Li]

On 2024/1/3 09:52, David Rientjes wrote:
> 
> I tested 1GB hugetlb on a smaller AMD host with the following:
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3301,7 +3301,7 @@ int alloc_bootmem_huge_page(struct hstate *h, int nid)
>   int __alloc_bootmem_huge_page(struct hstate *h, int nid)
>   {
>          struct huge_bootmem_page *m = NULL; /* initialize for clang */
> -       int nr_nodes, node;
> +       int nr_nodes, node = nid;
>   
>          /* do node specific alloc */
>          if (nid != NUMA_NO_NODE) {
> 

Oh, if nid != NUMA_NO_NODE and memblock_alloc_try_nid_raw succeed,
`node` must take the value of `nid`.

Otherwise, list_add(&m->list, &huge_boot_pages[node]) will not be
executed correctly.

> After the build error is fixed, feel free to add:
> 
> 	Tested-by: David Rientjes <rientjes@google.com>
> 

Thanks!

> to each patch.  I think Andrew will probably take a build fix up as a
> delta on top of patch 4 rather than sending a whole new series unless
> there is other feedback that you receive.

Re: [PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to_alloc

[Gang Li]

On 2024/1/3 09:32, David Rientjes wrote:
> Same error as v2:
> 
> mm/hugetlb.c:3315:53: warning: variable 'node' is used uninitialized whenever '&&' condition is false [-Wsometimes-uninitialized]
>          for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
>          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> mm/hugetlb.c:1501:3: note: expanded from macro 'for_each_node_mask_to_alloc'
>                  nr_nodes > 0 &&                                         \
>                  ^~~~~~~~~~~~
> mm/hugetlb.c:3342:38: note: uninitialized use occurs here
>          list_add(&m->list, &huge_boot_pages[node]);
>                                              ^~~~
> mm/hugetlb.c:3315:53: note: remove the '&&' if its condition is always true
>          for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
>                                                             ^
> mm/hugetlb.c:3310:7: warning: variable 'node' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>                  if (!m)
>                      ^~
> mm/hugetlb.c:3342:38: note: uninitialized use occurs here
>          list_add(&m->list, &huge_boot_pages[node]);
>                                              ^~~~
> mm/hugetlb.c:3310:3: note: remove the 'if' if its condition is always true
>                  if (!m)
>                  ^~~~~~~
> mm/hugetlb.c:3304:20: note: initialize the variable 'node' to silence this warning
>          int nr_nodes, node;
>                            ^
>                             = 0
> 2 warnings generated.
> 

How did you get those warnings? I got nothing in my compilation.

Re: [PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to_alloc

[David Rientjes]

On Wed, 3 Jan 2024, Gang Li wrote:

> On 2024/1/3 09:32, David Rientjes wrote:
> > Same error as v2:
> > 
> > mm/hugetlb.c:3315:53: warning: variable 'node' is used uninitialized
> > whenever '&&' condition is false [-Wsometimes-uninitialized]
> >          for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node,
> > &node_states[N_MEMORY]) {
> >          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > mm/hugetlb.c:1501:3: note: expanded from macro 'for_each_node_mask_to_alloc'
> >                  nr_nodes > 0 &&                                         \
> >                  ^~~~~~~~~~~~
> > mm/hugetlb.c:3342:38: note: uninitialized use occurs here
> >          list_add(&m->list, &huge_boot_pages[node]);
> >                                              ^~~~
> > mm/hugetlb.c:3315:53: note: remove the '&&' if its condition is always true
> >          for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node,
> > &node_states[N_MEMORY]) {
> >                                                             ^
> > mm/hugetlb.c:3310:7: warning: variable 'node' is used uninitialized whenever
> > 'if' condition is false [-Wsometimes-uninitialized]
> >                  if (!m)
> >                      ^~
> > mm/hugetlb.c:3342:38: note: uninitialized use occurs here
> >          list_add(&m->list, &huge_boot_pages[node]);
> >                                              ^~~~
> > mm/hugetlb.c:3310:3: note: remove the 'if' if its condition is always true
> >                  if (!m)
> >                  ^~~~~~~
> > mm/hugetlb.c:3304:20: note: initialize the variable 'node' to silence this
> > warning
> >          int nr_nodes, node;
> >                            ^
> >                             = 0
> > 2 warnings generated.
> > 
> 
> How did you get those warnings? I got nothing in my compilation.
> 

I'm using clang.

You spotted the issue in your earlier reply about the potentially 
uninitialized use of "node" when adding to the list.

Re: [PATCH v3 1/7] hugetlb: code clean for hugetlb_hstate_alloc_pages

[Muchun Song]

On 2024/1/2 21:12, Gang Li wrote:
> The readability of `hugetlb_hstate_alloc_pages` is poor. By cleaning the
> code, its readability can be improved, facilitating future modifications.
>
> This patch extracts two functions to reduce the complexity of
> `hugetlb_hstate_alloc_pages` and has no functional changes.
>
> - hugetlb_hstate_alloc_pages_node_specific() to handle iterates through
>    each online node and performs allocation if necessary.
> - hugetlb_hstate_alloc_pages_report() report error during allocation.
>    And the value of h->max_huge_pages is updated accordingly.
>
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
>   mm/hugetlb.c | 46 +++++++++++++++++++++++++++++-----------------
>   1 file changed, 29 insertions(+), 17 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ed1581b670d42..2606135ec55e6 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3482,6 +3482,33 @@ static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
>   	h->max_huge_pages_node[nid] = i;
>   }
>   
> +static bool __init hugetlb_hstate_alloc_pages_node_specific(struct hstate *h)

I'd like to rename this to hugetlb_hstate_alloc_pages_specific_nodes.

Otherwise, LGTM.

Reviewed-by: Muchun Song <muchun.song@linux.dev>

> +{
> +	int i;
> +	bool node_specific_alloc = false;
> +
> +	for_each_online_node(i) {
> +		if (h->max_huge_pages_node[i] > 0) {
> +			hugetlb_hstate_alloc_pages_onenode(h, i);
> +			node_specific_alloc = true;
> +		}
> +	}
> +
> +	return node_specific_alloc;
> +}
> +
> +static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, struct hstate *h)
> +{
> +	if (allocated < h->max_huge_pages) {
> +		char buf[32];
> +
> +		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
> +		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
> +			h->max_huge_pages, buf, allocated);
> +		h->max_huge_pages = allocated;
> +	}
> +}
> +
>   /*
>    * NOTE: this routine is called in different contexts for gigantic and
>    * non-gigantic pages.
> @@ -3499,7 +3526,6 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   	struct folio *folio;
>   	LIST_HEAD(folio_list);
>   	nodemask_t *node_alloc_noretry;
> -	bool node_specific_alloc = false;
>   
>   	/* skip gigantic hugepages allocation if hugetlb_cma enabled */
>   	if (hstate_is_gigantic(h) && hugetlb_cma_size) {
> @@ -3508,14 +3534,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   	}
>   
>   	/* do node specific alloc */
> -	for_each_online_node(i) {
> -		if (h->max_huge_pages_node[i] > 0) {
> -			hugetlb_hstate_alloc_pages_onenode(h, i);
> -			node_specific_alloc = true;
> -		}
> -	}
> -
> -	if (node_specific_alloc)
> +	if (hugetlb_hstate_alloc_pages_node_specific(h))
>   		return;
>   
>   	/* below will do all node balanced alloc */
> @@ -3558,14 +3577,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   	/* list will be empty if hstate_is_gigantic */
>   	prep_and_add_allocated_folios(h, &folio_list);
>   
> -	if (i < h->max_huge_pages) {
> -		char buf[32];
> -
> -		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
> -		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
> -			h->max_huge_pages, buf, i);
> -		h->max_huge_pages = i;
> -	}
> +	hugetlb_hstate_alloc_pages_report(i, h);
>   	kfree(node_alloc_noretry);
>   }
>   

Re: [PATCH v3 1/7] hugetlb: code clean for hugetlb_hstate_alloc_pages

[Tim Chen]

On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
> The readability of `hugetlb_hstate_alloc_pages` is poor. By cleaning the
> code, its readability can be improved, facilitating future modifications.
> 
> This patch extracts two functions to reduce the complexity of
> `hugetlb_hstate_alloc_pages` and has no functional changes.
> 
> - hugetlb_hstate_alloc_pages_node_specific() to handle iterates through
>   each online node and performs allocation if necessary.
> - hugetlb_hstate_alloc_pages_report() report error during allocation.
>   And the value of h->max_huge_pages is updated accordingly.

Minor nit, I think hugetlb_hstate_alloc_pages_errcheck() is more
descriptive than hugetlb_hstate_alloc_pages_report().

Otherwise

Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>

> 
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
>  mm/hugetlb.c | 46 +++++++++++++++++++++++++++++-----------------
>  1 file changed, 29 insertions(+), 17 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ed1581b670d42..2606135ec55e6 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3482,6 +3482,33 @@ static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
>  	h->max_huge_pages_node[nid] = i;
>  }
>  
> +static bool __init hugetlb_hstate_alloc_pages_node_specific(struct hstate *h)
> +{
> +	int i;
> +	bool node_specific_alloc = false;
> +
> +	for_each_online_node(i) {
> +		if (h->max_huge_pages_node[i] > 0) {
> +			hugetlb_hstate_alloc_pages_onenode(h, i);
> +			node_specific_alloc = true;
> +		}
> +	}
> +
> +	return node_specific_alloc;
> +}
> +
> +static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, struct hstate *h)
> +{
> +	if (allocated < h->max_huge_pages) {
> +		char buf[32];
> +
> +		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
> +		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
> +			h->max_huge_pages, buf, allocated);
> +		h->max_huge_pages = allocated;
> +	}
> +}
> +
>  /*
>   * NOTE: this routine is called in different contexts for gigantic and
>   * non-gigantic pages.
> @@ -3499,7 +3526,6 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  	struct folio *folio;
>  	LIST_HEAD(folio_list);
>  	nodemask_t *node_alloc_noretry;
> -	bool node_specific_alloc = false;
>  
>  	/* skip gigantic hugepages allocation if hugetlb_cma enabled */
>  	if (hstate_is_gigantic(h) && hugetlb_cma_size) {
> @@ -3508,14 +3534,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  	}
>  
>  	/* do node specific alloc */
> -	for_each_online_node(i) {
> -		if (h->max_huge_pages_node[i] > 0) {
> -			hugetlb_hstate_alloc_pages_onenode(h, i);
> -			node_specific_alloc = true;
> -		}
> -	}
> -
> -	if (node_specific_alloc)
> +	if (hugetlb_hstate_alloc_pages_node_specific(h))
>  		return;
>  
>  	/* below will do all node balanced alloc */
> @@ -3558,14 +3577,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  	/* list will be empty if hstate_is_gigantic */
>  	prep_and_add_allocated_folios(h, &folio_list);
>  
> -	if (i < h->max_huge_pages) {
> -		char buf[32];
> -
> -		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
> -		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
> -			h->max_huge_pages, buf, i);
> -		h->max_huge_pages = i;
> -	}
> +	hugetlb_hstate_alloc_pages_report(i, h);
>  	kfree(node_alloc_noretry);
>  }
>  

Re: [PATCH v3 2/7] hugetlb: split hugetlb_hstate_alloc_pages

[Tim Chen]

On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
> 1G and 2M huge pages have different allocation and initialization logic,
> which leads to subtle differences in parallelization. Therefore, it is
> appropriate to split hugetlb_hstate_alloc_pages into gigantic and
> non-gigantic.
> 
> This patch has no functional changes.
> 
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
>  mm/hugetlb.c | 86 +++++++++++++++++++++++++++-------------------------
>  1 file changed, 45 insertions(+), 41 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2606135ec55e6..92448e747991d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3509,6 +3509,47 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
>  	}
>  }
>  
> +static unsigned long __init hugetlb_hstate_alloc_pages_gigantic(struct hstate *h)
> +{
> +	unsigned long i;
> +
> +	for (i = 0; i < h->max_huge_pages; ++i) {
> +		/*
> +		 * gigantic pages not added to list as they are not
> +		 * added to pools now.
> +		 */

This comment unnecessary as now we don't have mix gigantic and non-gigantic code,
which uses foilio list.  And folio_list is not in this routine.

Can be removed.

Otherwise Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>

> +		if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
> +			break;
> +		cond_resched();
> +	}
> +
> +	return i;
> +}
> +
> +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);
> +
> +	return i;
> +}
> +
>  /*
>   * NOTE: this routine is called in different contexts for gigantic and
>   * non-gigantic pages.
> @@ -3522,10 +3563,7 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
>   */
>  static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  {
> -	unsigned long i;
> -	struct folio *folio;
> -	LIST_HEAD(folio_list);
> -	nodemask_t *node_alloc_noretry;
> +	unsigned long allocated;
>  
>  	/* skip gigantic hugepages allocation if hugetlb_cma enabled */
>  	if (hstate_is_gigantic(h) && hugetlb_cma_size) {
> @@ -3539,46 +3577,12 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  
>  	/* below will do all node balanced alloc */
>  	if (!hstate_is_gigantic(h)) {
> -		/*
> -		 * Bit mask controlling how hard we retry per-node allocations.
> -		 * Ignore errors as lower level routines can deal with
> -		 * node_alloc_noretry == NULL.  If this kmalloc fails at boot
> -		 * time, we are likely in bigger trouble.
> -		 */
> -		node_alloc_noretry = kmalloc(sizeof(*node_alloc_noretry),
> -						GFP_KERNEL);
> +		allocated = hugetlb_hstate_alloc_pages_non_gigantic(h);
>  	} else {
> -		/* allocations done at boot time */
> -		node_alloc_noretry = NULL;
> -	}
> -
> -	/* bit mask controlling how hard we retry per-node allocations */
> -	if (node_alloc_noretry)
> -		nodes_clear(*node_alloc_noretry);
> -
> -	for (i = 0; i < h->max_huge_pages; ++i) {
> -		if (hstate_is_gigantic(h)) {
> -			/*
> -			 * gigantic pages not added to list as they are not
> -			 * added to pools now.
> -			 */
> -			if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
> -				break;
> -		} else {
> -			folio = alloc_pool_huge_folio(h, &node_states[N_MEMORY],
> -							node_alloc_noretry);
> -			if (!folio)
> -				break;
> -			list_add(&folio->lru, &folio_list);
> -		}
> -		cond_resched();
> +		allocated = hugetlb_hstate_alloc_pages_gigantic(h);
>  	}
>  
> -	/* list will be empty if hstate_is_gigantic */
> -	prep_and_add_allocated_folios(h, &folio_list);
> -
> -	hugetlb_hstate_alloc_pages_report(i, h);
> -	kfree(node_alloc_noretry);
> +	hugetlb_hstate_alloc_pages_report(allocated, h);
>  }
>  
>  static void __init hugetlb_init_hstates(void)

Re: [PATCH v3 1/7] hugetlb: code clean for hugetlb_hstate_alloc_pages

[Gang Li]

On 2024/1/10 18:19, Muchun Song wrote:
> 
> 
> On 2024/1/2 21:12, Gang Li wrote:
>> The readability of `hugetlb_hstate_alloc_pages` is poor. By cleaning the
>> code, its readability can be improved, facilitating future modifications.
>>
>> This patch extracts two functions to reduce the complexity of
>> `hugetlb_hstate_alloc_pages` and has no functional changes.
>>
>> - hugetlb_hstate_alloc_pages_node_specific() to handle iterates through
>>    each online node and performs allocation if necessary.
>> - hugetlb_hstate_alloc_pages_report() report error during allocation.
>>    And the value of h->max_huge_pages is updated accordingly.
>>
>> Signed-off-by: Gang Li <gang.li@linux.dev>
>> ---
>>   mm/hugetlb.c | 46 +++++++++++++++++++++++++++++-----------------
>>   1 file changed, 29 insertions(+), 17 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index ed1581b670d42..2606135ec55e6 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -3482,6 +3482,33 @@ static void __init 
>> hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
>>       h->max_huge_pages_node[nid] = i;
>>   }
>> +static bool __init hugetlb_hstate_alloc_pages_node_specific(struct 
>> hstate *h)
> 
> I'd like to rename this to hugetlb_hstate_alloc_pages_specific_nodes.
> 
> Otherwise, LGTM.
> 
> Reviewed-by: Muchun Song <muchun.song@linux.dev>
> 

Thanks! I will adjust it in the next version.

Re: [PATCH v3 1/7] hugetlb: code clean for hugetlb_hstate_alloc_pages

[Gang Li]

On 2024/1/11 05:55, Tim Chen wrote:
> On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
>> The readability of `hugetlb_hstate_alloc_pages` is poor. By cleaning the
>> code, its readability can be improved, facilitating future modifications.
>>
>> This patch extracts two functions to reduce the complexity of
>> `hugetlb_hstate_alloc_pages` and has no functional changes.
>>
>> - hugetlb_hstate_alloc_pages_node_specific() to handle iterates through
>>    each online node and performs allocation if necessary.
>> - hugetlb_hstate_alloc_pages_report() report error during allocation.
>>    And the value of h->max_huge_pages is updated accordingly.
> 
> Minor nit, I think hugetlb_hstate_alloc_pages_errcheck() is more
> descriptive than hugetlb_hstate_alloc_pages_report().

Thanks! This looks more intuitive.

> 
> Otherwise
> 
> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
> 

Re: [PATCH v3 2/7] hugetlb: split hugetlb_hstate_alloc_pages

[Gang Li]

On 2024/1/11 07:12, Tim Chen wrote:
> On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
>> +static unsigned long __init hugetlb_hstate_alloc_pages_gigantic(struct hstate *h)
>> +{
>> +	unsigned long i;
>> +
>> +	for (i = 0; i < h->max_huge_pages; ++i) {
>> +		/*
>> +		 * gigantic pages not added to list as they are not
>> +		 * added to pools now.
>> +		 */
> 
> This comment unnecessary as now we don't have mix gigantic and non-gigantic code,
> which uses foilio list.  And folio_list is not in this routine.
> 
> Can be removed.
> 
> Otherwise Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
> 

Thanks!

Re: [PATCH v3 3/7] padata: dispatch works on different nodes

[Tim Chen]

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@linux.dev>
> ---
>  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;  

>  
>  	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

> +		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 89dc29f1e6c6f..59fcffddf65a3 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -2225,6 +2225,7 @@ 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);

Re: [PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to_alloc

[Tim Chen]

On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
> The parallelization of hugetlb allocation leads to errors when sharing
> h->next_nid_to_alloc across different threads. To address this, it's

Suggest you say
With parallelization of hugetlb allocation across different threads,
each thread works on a differnet node to allocate pages from, instead
of all allocating from a common node h->next_nid_to_alloc.  To address this, it's

> necessary to assign a separate next_nid_to_alloc for each thread.
> 
> Consequently, the hstate_next_node_to_alloc and for_each_node_mask_to_alloc
> have been modified to directly accept a *next_nid_to_alloc parameter,
> ensuring thread-specific allocation and avoiding concurrent access issues.
> 
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
> This patch seems not elegant, but I can't come up with anything better.
> Any suggestions will be highly appreciated!
> ---
>  mm/hugetlb.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 92448e747991d..a71bc1622b53b 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1464,15 +1464,15 @@ static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
>   * next node from which to allocate, handling wrap at end of node
>   * mask.
>   */
> -static int hstate_next_node_to_alloc(struct hstate *h,
> +static int hstate_next_node_to_alloc(int *next_nid_to_alloc,
>  					nodemask_t *nodes_allowed)
>  {
>  	int nid;
>  
>  	VM_BUG_ON(!nodes_allowed);
>  
> -	nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
> -	h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
> +	nid = get_valid_node_allowed(*next_nid_to_alloc, nodes_allowed);
> +	*next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
>  
>  	return nid;
>  }
> @@ -1495,10 +1495,10 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
>  	return nid;
>  }
>  
> -#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask)		\
> +#define for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, mask)		\
>  	for (nr_nodes = nodes_weight(*mask);				\
>  		nr_nodes > 0 &&						\
> -		((node = hstate_next_node_to_alloc(hs, mask)) || 1);	\
> +		((node = hstate_next_node_to_alloc(next_nid_to_alloc, mask)) || 1);	\
>  		nr_nodes--)
>  
>  #define for_each_node_mask_to_free(hs, nr_nodes, node, mask)		\
> @@ -2350,12 +2350,13 @@ static void prep_and_add_allocated_folios(struct hstate *h,
>   */
>  static struct folio *alloc_pool_huge_folio(struct hstate *h,
>  					nodemask_t *nodes_allowed,
> -					nodemask_t *node_alloc_noretry)
> +					nodemask_t *node_alloc_noretry,
> +					int *next_nid_to_alloc)
>  {
>  	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
>  	int nr_nodes, node;
>  
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +	for_each_node_mask_to_alloc(next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
>  		struct folio *folio;
>  
>  		folio = only_alloc_fresh_hugetlb_folio(h, gfp_mask, node,
> @@ -3310,7 +3311,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid)
>  		goto found;
>  	}
>  	/* allocate from next node when distributing huge pages */
> -	for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> +	for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
>  		m = memblock_alloc_try_nid_raw(
>  				huge_page_size(h), huge_page_size(h),
>  				0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
> @@ -3684,7 +3685,7 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
>  	VM_BUG_ON(delta != -1 && delta != 1);
>  
>  	if (delta < 0) {
> -		for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> +		for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
>  			if (h->surplus_huge_pages_node[node])
>  				goto found;
>  		}
> @@ -3799,7 +3800,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
>  		cond_resched();
>  
>  		folio = alloc_pool_huge_folio(h, nodes_allowed,
> -						node_alloc_noretry);
> +						node_alloc_noretry,
> +						&h->next_nid_to_alloc);
>  		if (!folio) {
>  			prep_and_add_allocated_folios(h, &page_list);
>  			spin_lock_irq(&hugetlb_lock);

Re: [PATCH v3 5/7] hugetlb: have CONFIG_HUGETLBFS select CONFIG_PADATA

[Tim Chen]

On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
> Now hugetlb uses padata_do_multithreaded for parallel initialization,
> so select CONFIG_PADATA.

Perhaps rephrase

Allow hugetlb use padata_do_multithreaded for parallel initialization.
Select CONFIG_PADATA in this case.

> 
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
>  fs/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 89fdbefd1075f..a57d6e6c41e6f 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -262,6 +262,7 @@ menuconfig HUGETLBFS
>  	depends on X86 || SPARC64 || ARCH_SUPPORTS_HUGETLBFS || BROKEN
>  	depends on (SYSFS || SYSCTL)
>  	select MEMFD_CREATE
> +	select PADATA
>  	help
>  	  hugetlbfs is a filesystem backing for HugeTLB pages, based on
>  	  ramfs. For architectures that support it, say Y here and read

Re: [PATCH v3 3/7] padata: dispatch works on different nodes

[Gang Li]

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@linux.dev>
>> ---
>>   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.

Re: [PATCH v3 4/7] hugetlb: pass *next_nid_to_alloc directly to for_each_node_mask_to_alloc

[Gang Li]

On 2024/1/12 06:21, Tim Chen wrote:
> On Tue, 2024-01-02 at 21:12 +0800, Gang Li wrote:
>> The parallelization of hugetlb allocation leads to errors when sharing
>> h->next_nid_to_alloc across different threads. To address this, it's
> 
> Suggest you say
> With parallelization of hugetlb allocation across different threads,
> each thread works on a differnet node to allocate pages from, instead
> of all allocating from a common node h->next_nid_to_alloc.  To address this, it's
> 
>> necessary to assign a separate next_nid_to_alloc for each thread.

LGTM, thanks.

Re: [PATCH v3 3/7] padata: dispatch works on different nodes

[Tim Chen]

On Fri, 2024-01-12 at 15:09 +0800, Gang Li wrote:
> 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@linux.dev>
> > > ---
> > >   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;

Thinking more about it, there could still be multiple threads working
at the same time with stale global_nid.  We should probably do a compare
exchange of global_nid with new nid only if the global nid was unchanged.
Otherwise we should go to the next node with the changed global nid before
we queue the job.

Tim

> 
>          /* 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.

Re: [PATCH v3 3/7] padata: dispatch works on different nodes

[Gang Li]

On 2024/1/13 02:27, Tim Chen wrote:
> On Fri, 2024-01-12 at 15:09 +0800, Gang Li wrote:
>> 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@linux.dev>
>>>> ---
>>>>    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;
> 
> Thinking more about it, there could still be multiple threads working
> at the same time with stale global_nid.  We should probably do a compare
> exchange of global_nid with new nid only if the global nid was unchanged.
> Otherwise we should go to the next node with the changed global nid before
> we queue the job.
> 
> Tim
> 
How about:
```
nid = global_nid;
list_for_each_entry(pw, &works, pw_list)
	if (job->numa_aware) {
		int old_node = nid;
		queue_work_node(nid, system_unbound_wq, &pw->pw_work);
		nid = next_node(nid, node_states[N_CPU]);
		cmpxchg(&global_nid, old_node, nid);
	} else
		queue_work(system_unbound_wq, &pw->pw_work);

```

Re: [PATCH v3 2/7] hugetlb: split hugetlb_hstate_alloc_pages

[Muchun Song]

On 2024/1/2 21:12, Gang Li wrote:
> 1G and 2M huge pages have different allocation and initialization logic,
> which leads to subtle differences in parallelization. Therefore, it is
> appropriate to split hugetlb_hstate_alloc_pages into gigantic and
> non-gigantic.
>
> This patch has no functional changes.
>
> Signed-off-by: Gang Li <gang.li@linux.dev>
> ---
>   mm/hugetlb.c | 86 +++++++++++++++++++++++++++-------------------------
>   1 file changed, 45 insertions(+), 41 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2606135ec55e6..92448e747991d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3509,6 +3509,47 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
>   	}
>   }
>   
> +static unsigned long __init hugetlb_hstate_alloc_pages_gigantic(struct hstate *h)

The name is so long, how about hugetlb_gigantic_pages_alloc_boot?

> +{
> +	unsigned long i;
> +
> +	for (i = 0; i < h->max_huge_pages; ++i) {
> +		/*
> +		 * gigantic pages not added to list as they are not
> +		 * added to pools now.
> +		 */
> +		if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
> +			break;
> +		cond_resched();
> +	}
> +
> +	return i;
> +}
> +
> +static unsigned long __init hugetlb_hstate_alloc_pages_non_gigantic(struct hstate *h)

hugetlb_pages_alloc_boot?

> +{
> +	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);
> +
> +	return i;
> +}
> +
>   /*
>    * NOTE: this routine is called in different contexts for gigantic and
>    * non-gigantic pages.
> @@ -3522,10 +3563,7 @@ static void __init hugetlb_hstate_alloc_pages_report(unsigned long allocated, st
>    */
>   static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   {
> -	unsigned long i;
> -	struct folio *folio;
> -	LIST_HEAD(folio_list);
> -	nodemask_t *node_alloc_noretry;
> +	unsigned long allocated;
>   
>   	/* skip gigantic hugepages allocation if hugetlb_cma enabled */
>   	if (hstate_is_gigantic(h) && hugetlb_cma_size) {
> @@ -3539,46 +3577,12 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   
>   	/* below will do all node balanced alloc */
>   	if (!hstate_is_gigantic(h)) {

It it unnecessary to reverse the condition. A little sime like following:

if (hstate_is_gigantic(h))
     /* gigantic pages */
else
     /* normal pages */

> -		/*
> -		 * Bit mask controlling how hard we retry per-node allocations.
> -		 * Ignore errors as lower level routines can deal with
> -		 * node_alloc_noretry == NULL.  If this kmalloc fails at boot
> -		 * time, we are likely in bigger trouble.
> -		 */
> -		node_alloc_noretry = kmalloc(sizeof(*node_alloc_noretry),
> -						GFP_KERNEL);
> +		allocated = hugetlb_hstate_alloc_pages_non_gigantic(h);
>   	} else {
> -		/* allocations done at boot time */
> -		node_alloc_noretry = NULL;
> -	}
> -
> -	/* bit mask controlling how hard we retry per-node allocations */
> -	if (node_alloc_noretry)
> -		nodes_clear(*node_alloc_noretry);
> -
> -	for (i = 0; i < h->max_huge_pages; ++i) {
> -		if (hstate_is_gigantic(h)) {
> -			/*
> -			 * gigantic pages not added to list as they are not
> -			 * added to pools now.
> -			 */
> -			if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
> -				break;
> -		} else {
> -			folio = alloc_pool_huge_folio(h, &node_states[N_MEMORY],
> -							node_alloc_noretry);
> -			if (!folio)
> -				break;
> -			list_add(&folio->lru, &folio_list);
> -		}
> -		cond_resched();
> +		allocated = hugetlb_hstate_alloc_pages_gigantic(h);
>   	}
>   
> -	/* list will be empty if hstate_is_gigantic */
> -	prep_and_add_allocated_folios(h, &folio_list);
> -
> -	hugetlb_hstate_alloc_pages_report(i, h);
> -	kfree(node_alloc_noretry);
> +	hugetlb_hstate_alloc_pages_report(allocated, h);
>   }
>   
>   static void __init hugetlb_init_hstates(void)

Re: [PATCH v3 2/7] hugetlb: split hugetlb_hstate_alloc_pages

[Gang Li]

On 2024/1/16 15:02, Muchun Song wrote:
> On 2024/1/2 21:12, Gang Li wrote:
>> hugetlb_hstate_alloc_pages_gigantic(struct hstate *h)
> 
> The name is so long, how about hugetlb_gigantic_pages_alloc_boot?
> 
>> hugetlb_hstate_alloc_pages_non_gigantic(struct hstate *h)
> 
> hugetlb_pages_alloc_boot?
LGTM.

> It it unnecessary to reverse the condition. A little sime like following:
> 
> if (hstate_is_gigantic(h))
>     /* gigantic pages */
> else
>     /* normal pages */

Will take it in next version.

Re: [PATCH v3 5/7] hugetlb: have CONFIG_HUGETLBFS select CONFIG_PADATA

[Muchun Song]

> On Jan 2, 2024, at 21:12, Gang Li <gang.li@linux.dev> wrote:
> 
> Now hugetlb uses padata_do_multithreaded for parallel initialization,
> so select CONFIG_PADATA.
> 
> Signed-off-by: Gang Li <gang.li@linux.dev>

Reviewed-by: Muchun Song <muchun.song@linux.dev>

Re: [PATCH v3 3/7] padata: dispatch works on different nodes

[Tim Chen]

On Mon, 2024-01-15 at 16:57 +0800, Gang Li wrote:
> 
> On 2024/1/13 02:27, Tim Chen wrote:
> > On Fri, 2024-01-12 at 15:09 +0800, Gang Li wrote:
> > > 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@linux.dev>
> > > > > ---
> > > > >    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;
> > 
> > Thinking more about it, there could still be multiple threads working
> > at the same time with stale global_nid.  We should probably do a compare
> > exchange of global_nid with new nid only if the global nid was unchanged.
> > Otherwise we should go to the next node with the changed global nid before
> > we queue the job.
> > 
> > Tim
> > 
> How about:
> ```
> nid = global_nid;
> list_for_each_entry(pw, &works, pw_list)
> 	if (job->numa_aware) {
> 		int old_node = nid;
> 		queue_work_node(nid, system_unbound_wq, &pw->pw_work);
> 		nid = next_node(nid, node_states[N_CPU]);
> 		cmpxchg(&global_nid, old_node, nid);
> 	} else
> 		queue_work(system_unbound_wq, &pw->pw_work);
> 
> ```
> 

I am thinking something like

static volatile atomic_t last_used_nid;

list_for_each_entry(pw, &works, pw_list)
 	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);
	}

Note that we need to use next_node_in so we'll wrap around the node mask.

Tim

Re: [PATCH v3 3/7] padata: dispatch works on different nodes

[Gang Li]

Hi Tim,

On 2024/1/18 06:14, Tim Chen wrote:
> On Mon, 2024-01-15 at 16:57 +0800, Gang Li wrote:
>> How about:
>> ```
>> nid = global_nid;
>> list_for_each_entry(pw, &works, pw_list)
>> 	if (job->numa_aware) {
>> 		int old_node = nid;
>> 		queue_work_node(nid, system_unbound_wq, &pw->pw_work);
>> 		nid = next_node(nid, node_states[N_CPU]);
>> 		cmpxchg(&global_nid, old_node, nid);



>> 	} else
>> 		queue_work(system_unbound_wq, &pw->pw_work);
>>
>> ```
>>

My original idea was to have all tasks from a single
padata_do_multithreaded distributed continuously across NUMA nodes.

In that case, the task distribution would be predictable for a single
padata_do_multithreaded call.

> 
> I am thinking something like
> 
> static volatile atomic_t last_used_nid;
> 
> list_for_each_entry(pw, &works, pw_list)
>   	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));


However, having the tasks from all parallel padata_do_multithreaded
globally distributed across NUMA nodes is also fine by me.

I don't have a strong preference.

>   		queue_work_node(nid, system_unbound_wq, &pw->pw_work);		
>   	} else {
>   		queue_work(system_unbound_wq, &pw->pw_work);
> 	}
> 
> Note that we need to use next_node_in so we'll wrap around the node mask.
>