[PATCH] mm: thp: Add new kernel parameters transparent_hugepage_defrag/khugepaged_defrag

[Gavin Guo]

There is no way to set up the defrag options in boot time. And it's
useful to set it up by default instead of making it work by a
systemd/upstart service or put the command to set up defrag inside
/etc/rc.local.

Signed-off-by: Gavin Guo <gavin.guo@xxxxxxxxxxxxx>
---
 .../admin-guide/kernel-parameters.txt         | 18 ++++++++
 mm/huge_memory.c                              | 43 +++++++++++++++++++
 mm/khugepaged.c                               | 21 +++++++++
 3 files changed, 82 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6253849afac2..a9fd020d78db 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2149,6 +2149,16 @@
 	kgdbwait	[KGDB] Stop kernel execution and enter the
 			kernel debugger at the earliest opportunity.
 
+	khugepaged_defrag=
+			[KNL]
+			Format: { "0" | "1" }
+			0 - disable the defrag
+			1 - enable the defrag
+			Control the defrag efforts when generating the
+			transparent hugepages through khugepaged.
+			See Documentation/admin-guide/mm/transhuge.rst
+			for more details.
+
 	kmac=		[MIPS] korina ethernet MAC address.
 			Configure the RouterBoard 532 series on-chip
 			Ethernet adapter MAC address.
@@ -5146,6 +5156,14 @@
 			See Documentation/admin-guide/mm/transhuge.rst
 			for more details.
 
+	transparent_hugepage_defrag=
+			[KNL]
+			Format: [always|defer|defer+madvise|madvise|never]
+			Control the defrag efforts when generating the
+			transparent hugepages.
+			See Documentation/admin-guide/mm/transhuge.rst
+			for more details.
+
 	tsc=		Disable clocksource stability checks for TSC.
 			Format: <string>
 			[x86] reliable: mark tsc clocksource as reliable, this
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8091b780cd7a..86b20a3a1aac 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -481,6 +481,49 @@ static int __init setup_transparent_hugepage(char *str)
 }
 __setup("transparent_hugepage=", setup_transparent_hugepage);
 
+static int __init setup_transparent_hugepage_defrag(char *str)
+{
+	int ret = 0;
+	if (!str)
+		goto out;
+	if (!strcmp(str, "always")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+		ret = 1;
+	} else if (!strcmp(str, "defer+madvise")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+		ret = 1;
+	} else if (!strcmp(str, "defer")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+		ret = 1;
+	} else if (!strcmp(str, "madvise")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+		ret = 1;
+	} else if (!strcmp(str, "never")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+		ret = 1;
+	}
+out:
+	if (!ret)
+		pr_warn("transparent_hugepage_defrag= cannot parse, ignored\n");
+	return ret;
+}
+__setup("transparent_hugepage_defrag=", setup_transparent_hugepage_defrag);
+
 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 {
 	if (likely(vma->vm_flags & VM_WRITE))
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b043c40a21d4..39bbf2107a23 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -394,6 +394,27 @@ int __init khugepaged_init(void)
 	return 0;
 }
 
+static int __init setup_khugepaged_defrag(char *str)
+{
+	int ret = 0;
+	if (!str)
+		goto out;
+	if (!strcmp(str, "0")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG,
+			  &transparent_hugepage_flags);
+		ret = 1;
+	} else if (!strcmp(str, "1")) {
+		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG,
+			&transparent_hugepage_flags);
+		ret = 1;
+	}
+out:
+	if (!ret)
+		pr_warn("khugepaged_defrag= cannot parse, ignored\n");
+	return ret;
+}
+__setup("khugepaged_defrag=", setup_khugepaged_defrag);
+
 void __init khugepaged_destroy(void)
 {
 	kmem_cache_destroy(mm_slot_cache);
-- 
2.17.1