Currently THP do swap by default, user has no control of it.
But some applications are swap sensitive, this patch add a boot param
and sys file to make it configurable.
Signed-off-by: Bob Liu <lliubbo@xxxxxxxxx>
---
Documentation/vm/transhuge.txt | 9 +++++++++
include/linux/huge_mm.h | 5 +++++
mm/huge_memory.c | 26 ++++++++++++++++++++++++++
mm/swap_state.c | 10 ++++++----
4 files changed, 46 insertions(+), 4 deletions(-)
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index 29bdf62..1c7d8e9 100644
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -116,6 +116,12 @@ echo always >/sys/kernel/mm/transparent_hugepage/defrag
echo madvise >/sys/kernel/mm/transparent_hugepage/defrag
echo never >/sys/kernel/mm/transparent_hugepage/defrag
+Swap for Transparent Hugepage default is enabled, you can disable it
+by:
+echo 1 > /sys/kernel/mm/transparent_hugepage/disable_swap
+and reenable by:
+echo 0 > /sys/kernel/mm/transparent_hugepage/disable_swap
+
khugepaged will be automatically started when
transparent_hugepage/enabled is set to "always" or "madvise, and it'll
be automatically shutdown if it's set to "never".
@@ -159,6 +165,9 @@ Support by passing the parameter "transparent_hugepage=always" or
"transparent_hugepage=madvise" or "transparent_hugepage=never"
(without "") to the kernel command line.
+You can disable swap for Transparent Hugepage by passing parameter
+"disable_transparent_hugepage_swap".
+
== Need of application restart ==
The transparent_hugepage/enabled values only affect future
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 48c32eb..229ef7b 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -31,6 +31,7 @@ enum transparent_hugepage_flag {
TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG,
+ TRANSPARENT_HUGEPAGE_SWAP_DISABLE_FLAG,
#ifdef CONFIG_DEBUG_VM
TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG,
#endif
@@ -65,6 +66,9 @@ extern pmd_t *page_check_address_pmd(struct page *page,
(transparent_hugepage_flags & \
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG) && \
(__vma)->vm_flags & VM_HUGEPAGE))
+#define transparent_hugepage_swap_disable() \
+ (transparent_hugepage_flags & \
+ (1<<TRANSPARENT_HUGEPAGE_SWAP_DISABLE_FLAG))
#ifdef CONFIG_DEBUG_VM
#define transparent_hugepage_debug_cow() \
(transparent_hugepage_flags & \
@@ -148,6 +152,7 @@ static inline struct page *compound_trans_head(struct page *page)
#define hpage_nr_pages(x) 1
#define transparent_hugepage_enabled(__vma) 0
+#define transparent_hugepage_swap_disable() 0
#define transparent_hugepage_flags 0UL
static inline int split_huge_page(struct page *page)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e2d1587..31aba4b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -293,6 +293,22 @@ static ssize_t defrag_store(struct kobject *kobj,
static struct kobj_attribute defrag_attr =
__ATTR(defrag, 0644, defrag_show, defrag_store);
+static ssize_t disable_swap_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return single_flag_show(kobj, attr, buf,
+ TRANSPARENT_HUGEPAGE_SWAP_DISABLE_FLAG);
+}
+static ssize_t disable_swap_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ return single_flag_store(kobj, attr, buf, count,
+ TRANSPARENT_HUGEPAGE_SWAP_DISABLE_FLAG);
+}
+static struct kobj_attribute swap_attr =
+ __ATTR(disable_swap, 0644, disable_swap_show, disable_swap_store);
+
#ifdef CONFIG_DEBUG_VM
static ssize_t debug_cow_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
@@ -314,6 +330,7 @@ static struct kobj_attribute debug_cow_attr =
static struct attribute *hugepage_attr[] = {
&enabled_attr.attr,
&defrag_attr.attr,
+ &swap_attr.attr,
#ifdef CONFIG_DEBUG_VM
&debug_cow_attr.attr,
#endif
@@ -1408,6 +1425,15 @@ out:
return ret;
}
+static __init int disable_transparent_hugepage_swap(char *str)
+{
+ set_bit(TRANSPARENT_HUGEPAGE_SWAP_DISABLE_FLAG, &transparent_hugepage_flags);
+ printk(KERN_INFO "disable swap for transparent hugepage.\n");
+
+ return 0;
+}
+early_param("disable_transparent_hugepage_swap", disable_transparent_hugepage_swap);
+
#define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 4668046..3dfc4be 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -18,6 +18,7 @@
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/migrate.h>
+#include <linux/mm_inline.h>
#include <linux/page_cgroup.h>
#include <asm/pgtable.h>
@@ -155,10 +156,11 @@ int add_to_swap(struct page *page)
return 0;
if (unlikely(PageTransHuge(page)))
- if (unlikely(split_huge_page(page))) {
- swapcache_free(entry, NULL);
- return 0;
- }
+ if(!transparent_hugepage_swap_disable())
+ if (unlikely(split_huge_page(page))) {
+ swapcache_free(entry, NULL);
+ return 0;
+ }
/*
* Radix-tree node allocations from PF_MEMALLOC contexts could
--
1.5.6.3
--
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