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Subject[PATCH 4.19 48/49] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged
Date
From: Vijay Balakrishna <vijayb@linux.microsoft.com>

commit 4aab2be0983031a05cb4a19696c9da5749523426 upstream.

When memory is hotplug added or removed the min_free_kbytes should be
recalculated based on what is expected by khugepaged. Currently after
hotplug, min_free_kbytes will be set to a lower default and higher
default set when THP enabled is lost.

This change restores min_free_kbytes as expected for THP consumers.

[vijayb@linux.microsoft.com: v5]
Link: https://lkml.kernel.org/r/1601398153-5517-1-git-send-email-vijayb@linux.microsoft.com

Fixes: f000565adb77 ("thp: set recommended min free kbytes")
Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Allen Pais <apais@microsoft.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/1600305709-2319-2-git-send-email-vijayb@linux.microsoft.com
Link: https://lkml.kernel.org/r/1600204258-13683-1-git-send-email-vijayb@linux.microsoft.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/khugepaged.h | 5 +++++
mm/khugepaged.c | 13 +++++++++++--
mm/page_alloc.c | 3 +++
3 files changed, 19 insertions(+), 2 deletions(-)

--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -15,6 +15,7 @@ extern int __khugepaged_enter(struct mm_
extern void __khugepaged_exit(struct mm_struct *mm);
extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags);
+extern void khugepaged_min_free_kbytes_update(void);

#define khugepaged_enabled() \
(transparent_hugepage_flags & \
@@ -73,6 +74,10 @@ static inline int khugepaged_enter_vma_m
{
return 0;
}
+
+static inline void khugepaged_min_free_kbytes_update(void)
+{
+}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

#endif /* _LINUX_KHUGEPAGED_H */
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -53,6 +53,9 @@ enum scan_result {
#define CREATE_TRACE_POINTS
#include <trace/events/huge_memory.h>

+static struct task_struct *khugepaged_thread __read_mostly;
+static DEFINE_MUTEX(khugepaged_mutex);
+
/* default scan 8*512 pte (or vmas) every 30 second */
static unsigned int khugepaged_pages_to_scan __read_mostly;
static unsigned int khugepaged_pages_collapsed;
@@ -1952,8 +1955,6 @@ static void set_recommended_min_free_kby

int start_stop_khugepaged(void)
{
- static struct task_struct *khugepaged_thread __read_mostly;
- static DEFINE_MUTEX(khugepaged_mutex);
int err = 0;

mutex_lock(&khugepaged_mutex);
@@ -1980,3 +1981,11 @@ fail:
mutex_unlock(&khugepaged_mutex);
return err;
}
+
+void khugepaged_min_free_kbytes_update(void)
+{
+ mutex_lock(&khugepaged_mutex);
+ if (khugepaged_enabled() && khugepaged_thread)
+ set_recommended_min_free_kbytes();
+ mutex_unlock(&khugepaged_mutex);
+}
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -66,6 +66,7 @@
#include <linux/ftrace.h>
#include <linux/lockdep.h>
#include <linux/nmi.h>
+#include <linux/khugepaged.h>

#include <asm/sections.h>
#include <asm/tlbflush.h>
@@ -7399,6 +7400,8 @@ int __meminit init_per_zone_wmark_min(vo
setup_min_slab_ratio();
#endif

+ khugepaged_min_free_kbytes_update();
+
return 0;
}
postcore_initcall(init_per_zone_wmark_min)

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