The patch titled
pagemap clear_refs: modify to specify anon or mapped vma clearing
has been added to the -mm tree. Its filename is
pagemap-clear_refs-modify-to-specify-anon-or-mapped-vma-clearing.patch
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------------------------------------------------------
Subject: pagemap clear_refs: modify to specify anon or mapped vma clearing
From: "Moussa A. Ba" <moussa.a.ba@xxxxxxxxx>
Make the clear_refs proc interface a bit more versatile by adding support
for clearing anonymous pages, file mapped pages or both.
The patch adds anonymous and file backed filters to the clear_refs interface.
echo 1 > /proc/PID/clear_refs resets the bits on all pages
echo 2 > /proc/PID/clear_refs resets the bits on anonymous pages only
echo 3 > /proc/PID/clear_refs resets the bits on file backed pages only
Any other value is ignored
Signed-off-by: Moussa A. Ba <moussa.a.ba@xxxxxxxxx>
Signed-off-by: Jared E. Hulbert <jaredeh@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 13 ++++++++++++
fs/proc/task_mmu.c | 28 +++++++++++++++++++++++----
2 files changed, 37 insertions(+), 4 deletions(-)
diff -puN Documentation/filesystems/proc.txt~pagemap-clear_refs-modify-to-specify-anon-or-mapped-vma-clearing Documentation/filesystems/proc.txt
--- a/Documentation/filesystems/proc.txt~pagemap-clear_refs-modify-to-specify-anon-or-mapped-vma-clearing
+++ a/Documentation/filesystems/proc.txt
@@ -375,6 +375,19 @@ of memory currently marked as referenced
This file is only present if the CONFIG_MMU kernel configuration option is
enabled.
+The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
+bits on both physical and virtual pages associated with a process.
+To clear the bits for all the pages associated with the process
+ > echo 1 > /proc/PID/clear_refs
+
+To clear the bits for the anonymous pages associated with the process
+ > echo 2 > /proc/PID/clear_refs
+
+To clear the bits for the file mapped pages associated with the process
+ > echo 3 > /proc/PID/clear_refs
+Any other value written to /proc/PID/clear_refs will have no effect.
+
+
1.2 Kernel data
---------------
diff -puN fs/proc/task_mmu.c~pagemap-clear_refs-modify-to-specify-anon-or-mapped-vma-clearing fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~pagemap-clear_refs-modify-to-specify-anon-or-mapped-vma-clearing
+++ a/fs/proc/task_mmu.c
@@ -464,6 +464,10 @@ static int clear_refs_pte_range(pmd_t *p
return 0;
}
+#define CLEAR_REFS_ALL 1
+#define CLEAR_REFS_ANON 2
+#define CLEAR_REFS_MAPPED 3
+
static ssize_t clear_refs_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
@@ -471,13 +475,15 @@ static ssize_t clear_refs_write(struct f
char buffer[PROC_NUMBUF], *end;
struct mm_struct *mm;
struct vm_area_struct *vma;
+ int type;
memset(buffer, 0, sizeof(buffer));
if (count > sizeof(buffer) - 1)
count = sizeof(buffer) - 1;
if (copy_from_user(buffer, buf, count))
return -EFAULT;
- if (!simple_strtol(buffer, &end, 0))
+ type = simple_strtol(buffer, &end, 0);
+ if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
return -EINVAL;
if (*end == '\n')
end++;
@@ -493,9 +499,23 @@ static ssize_t clear_refs_write(struct f
down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
clear_refs_walk.private = vma;
- if (!is_vm_hugetlb_page(vma))
- walk_page_range(vma->vm_start, vma->vm_end,
- &clear_refs_walk);
+ if (is_vm_hugetlb_page(vma))
+ continue;
+ /*
+ * Writing 1 to /proc/pid/clear_refs affects all pages.
+ *
+ * Writing 2 to /proc/pid/clear_refs only affects
+ * Anonymous pages.
+ *
+ * Writing 3 to /proc/pid/clear_refs only affects file
+ * mapped pages.
+ */
+ if (type == CLEAR_REFS_ANON && vma->vm_file)
+ continue;
+ if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
+ continue;
+ walk_page_range(vma->vm_start, vma->vm_end,
+ &clear_refs_walk);
}
flush_tlb_mm(mm);
up_read(&mm->mmap_sem);
_
Patches currently in -mm which might be from moussa.a.ba@xxxxxxxxx are
pagemap-clear_refs-modify-to-specify-anon-or-mapped-vma-clearing.patch
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