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pagemap clear_refs: modify to specify anon or mapped vma clearing

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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>
This commit is contained in:
Moussa A. Ba 2009-09-21 17:02:29 -07:00 committed by Linus Torvalds
parent 7103ad323b
commit 398499d5f3
2 changed files with 37 additions and 4 deletions
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13
Documentation/filesystems/proc.txt
View File

@ -375,6 +375,19 @@ of memory currently marked as referenced or accessed.
This file is only present if the CONFIG_MMU kernel configuration option is This file is only present if the CONFIG_MMU kernel configuration option is
enabled. 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 1.2 Kernel data
--------------- ---------------

28
fs/proc/task_mmu.c
View File

@ -465,6 +465,10 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
return 0; 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, static ssize_t clear_refs_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos) size_t count, loff_t *ppos)
{ {
@ -472,13 +476,15 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
char buffer[PROC_NUMBUF], *end; char buffer[PROC_NUMBUF], *end;
struct mm_struct *mm; struct mm_struct *mm;
struct vm_area_struct *vma; struct vm_area_struct *vma;
int type;
memset(buffer, 0, sizeof(buffer)); memset(buffer, 0, sizeof(buffer));
if (count > sizeof(buffer) - 1) if (count > sizeof(buffer) - 1)
count = sizeof(buffer) - 1; count = sizeof(buffer) - 1;
if (copy_from_user(buffer, buf, count)) if (copy_from_user(buffer, buf, count))
return -EFAULT; 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; return -EINVAL;
if (*end == '\n') if (*end == '\n')
end++; end++;
@ -494,9 +500,23 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
down_read(&mm->mmap_sem); down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) { for (vma = mm->mmap; vma; vma = vma->vm_next) {
clear_refs_walk.private = vma; clear_refs_walk.private = vma;
if (!is_vm_hugetlb_page(vma)) if (is_vm_hugetlb_page(vma))
walk_page_range(vma->vm_start, vma->vm_end, continue;
&clear_refs_walk); /*
* 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); flush_tlb_mm(mm);
up_read(&mm->mmap_sem); up_read(&mm->mmap_sem);