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Date:   Wed,  6 May 2020 17:41:57 -0700
From:   Anthony Yznaga <anthony.yznaga@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     willy@...radead.org, corbet@....net, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        rppt@...ux.ibm.com, akpm@...ux-foundation.org, hughd@...gle.com,
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        ndesaulniers@...gle.com, dima@...ovin.in, daniel.kiper@...cle.com,
        nivedita@...m.mit.edu, rafael.j.wysocki@...el.com,
        dan.j.williams@...el.com, zhenzhong.duan@...cle.com,
        jroedel@...e.de, bhe@...hat.com, guro@...com,
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        lei.l.li@...el.com, paul.c.lai@...el.com, ashok.raj@...el.com,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: [RFC 31/43] memblock, mm: defer initialization of preserved pages

Preserved pages are represented in the memblock reserved list, but page
structs for pages in the reserved list are initialized early while boot
is single threaded which means that a large number of preserved pages
can impact boot time. To mitigate, defer initialization of preserved
pages by skipping them when other reserved pages are initialized and
initializing them later with a separate kernel thread.

Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
---
 arch/x86/mm/init_64.c |  1 -
 include/linux/mm.h    |  2 +-
 mm/memblock.c         | 10 ++++++++--
 mm/page_alloc.c       | 52 +++++++++++++++++++++++++++++++++++++++++++--------
 4 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 72662615977b..ae569ef6bd7d 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1245,7 +1245,6 @@ void __init mem_init(void)
 	after_bootmem = 1;
 	x86_init.hyper.init_after_bootmem();
 
-	pkram_free_pgt();
 	totalram_pages_add(pkram_reserved_pages);
 	/*
 	 * Must be done after boot memory is put on freelist, because here we
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5a323422d783..69b9cd08c721 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2297,7 +2297,7 @@ extern void free_highmem_page(struct page *page);
 extern void adjust_managed_page_count(struct page *page, long count);
 extern void mem_init_print_info(const char *str);
 
-extern void reserve_bootmem_region(phys_addr_t start, phys_addr_t end);
+extern void reserve_bootmem_region(phys_addr_t start, phys_addr_t end, int nid);
 
 /* Free the reserved page into the buddy system, so it gets managed. */
 static inline void __free_reserved_page(struct page *page)
diff --git a/mm/memblock.c b/mm/memblock.c
index 33597f352dc0..5524edbaf691 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -2042,11 +2042,17 @@ static unsigned long __init free_low_memory_core_early(void)
 	unsigned long count = 0;
 	phys_addr_t start, end;
 	u64 i;
+	enum memblock_flags exclude;
 
 	memblock_clear_hotplug(0, -1);
 
-	for_each_reserved_mem_region(i, &start, &end)
-		reserve_bootmem_region(start, end);
+	if (IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT))
+		exclude = MEMBLOCK_PRESERVED;
+	else
+		exclude = MEMBLOCK_NONE;
+
+	for_each_reserved_mem_range(i, 0, exclude, &start, &end, NULL)
+		reserve_bootmem_region(start, end, -1);
 
 	/*
 	 * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 69827d4fa052..afd97b31725e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -68,6 +68,7 @@
 #include <linux/lockdep.h>
 #include <linux/nmi.h>
 #include <linux/psi.h>
+#include <linux/pkram.h>
 
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
@@ -1408,15 +1409,18 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn,
 }
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
-static void __meminit init_reserved_page(unsigned long pfn)
+static void __meminit init_reserved_page(unsigned long pfn, int nid)
 {
 	pg_data_t *pgdat;
-	int nid, zid;
+	int zid;
 
-	if (!early_page_uninitialised(pfn))
-		return;
+	if (nid == -1) {
+		if (!early_page_uninitialised(pfn))
+			return;
+
+		nid = early_pfn_to_nid(pfn);
+	}
 
-	nid = early_pfn_to_nid(pfn);
 	pgdat = NODE_DATA(nid);
 
 	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
@@ -1428,7 +1432,7 @@ static void __meminit init_reserved_page(unsigned long pfn)
 	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
 }
 #else
-static inline void init_reserved_page(unsigned long pfn)
+static inline void init_reserved_page(unsigned long pfn, int nid)
 {
 }
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
@@ -1439,7 +1443,7 @@ static inline void init_reserved_page(unsigned long pfn)
  * marks the pages PageReserved. The remaining valid pages are later
  * sent to the buddy page allocator.
  */
-void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
+void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end, int nid)
 {
 	unsigned long start_pfn = PFN_DOWN(start);
 	unsigned long end_pfn = PFN_UP(end);
@@ -1448,7 +1452,7 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
 		if (pfn_valid(start_pfn)) {
 			struct page *page = pfn_to_page(start_pfn);
 
-			init_reserved_page(start_pfn);
+			init_reserved_page(start_pfn, nid);
 
 			/* Avoid false-positive PageTail() */
 			INIT_LIST_HEAD(&page->lru);
@@ -1876,6 +1880,34 @@ static int __init deferred_init_memmap(void *data)
 	return 0;
 }
 
+#ifdef CONFIG_PKRAM
+static int __init deferred_init_preserved(void *dummy)
+{
+	unsigned long start = jiffies;
+	unsigned long nr_pages = 0;
+	phys_addr_t spa, epa;
+	int nid;
+	u64 i;
+
+	for_each_reserved_mem_range(i, MEMBLOCK_PRESERVED, 0, &spa, &epa, &nid) {
+		reserve_bootmem_region(spa, epa, nid);
+		nr_pages += ((epa - spa) >> PAGE_SHIFT);
+	}
+
+	pr_info("initialised %lu preserved pages in %ums\n", nr_pages,
+					jiffies_to_msecs(jiffies - start));
+
+	/*
+	 * Free the preserved pages pagetable now that page structs are
+	 * initialized.
+	 */
+	pkram_free_pgt();
+
+	pgdat_init_report_one_done();
+	return 0;
+}
+#endif /* CONFIG_PKRAM */
+
 /*
  * If this zone has deferred pages, try to grow it by initializing enough
  * deferred pages to satisfy the allocation specified by order, rounded up to
@@ -1985,6 +2017,10 @@ void __init page_alloc_init_late(void)
 
 	/* There will be num_node_state(N_MEMORY) threads */
 	atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY));
+#ifdef CONFIG_PKRAM
+	atomic_inc(&pgdat_init_n_undone);
+	kthread_run(deferred_init_preserved, NULL, "pgdatainit_preserved");
+#endif
 	for_each_node_state(nid, N_MEMORY) {
 		kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid);
 	}
-- 
2.13.3

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