pagemap clear_refs: modify to specify anon or mapped vma clearing
The patch makes the clear_refs more versatile in adding the option to
select anonymous pages or file backed pages for clearing. This addition
has a measurable impact on user space application performance as it
decreases the number of pagewalks in scenarios where one is only
interested in a specific type of page (anonymous or file mapped).
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@gmail.com>
Signed-off-by: Jared E. Hulbert <jaredeh@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9bd8be1..59e98fe 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -465,6 +465,10 @@
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)
{
@@ -472,13 +476,15 @@
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++;
@@ -494,9 +500,23 @@
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);