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authorMoussa A. Ba <moussa.a.ba@gmail.com>2009-09-21 20:02:29 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 10:17:33 -0400
commit398499d5f3613c47f2143b8c54a04efb5d7a6da9 (patch)
tree0b337ca1d0e20caa2295c159d5c0deadf362e4a0
parent7103ad323b1ae32bedc3267402117e2f8b45e48d (diff)
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>
-rw-r--r--Documentation/filesystems/proc.txt13
-rw-r--r--fs/proc/task_mmu.c28
2 files changed, 37 insertions, 4 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 1c96cb6c7972..ae7f8bb1b7bc 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -375,6 +375,19 @@ of memory currently marked as referenced or accessed.
375This file is only present if the CONFIG_MMU kernel configuration option is 375This file is only present if the CONFIG_MMU kernel configuration option is
376enabled. 376enabled.
377 377
378The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
379bits on both physical and virtual pages associated with a process.
380To clear the bits for all the pages associated with the process
381 > echo 1 > /proc/PID/clear_refs
382
383To clear the bits for the anonymous pages associated with the process
384 > echo 2 > /proc/PID/clear_refs
385
386To clear the bits for the file mapped pages associated with the process
387 > echo 3 > /proc/PID/clear_refs
388Any other value written to /proc/PID/clear_refs will have no effect.
389
390
3781.2 Kernel data 3911.2 Kernel data
379--------------- 392---------------
380 393
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9bd8be1d235c..59e98fea34a4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -465,6 +465,10 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
465 return 0; 465 return 0;
466} 466}
467 467
468#define CLEAR_REFS_ALL 1
469#define CLEAR_REFS_ANON 2
470#define CLEAR_REFS_MAPPED 3
471
468static ssize_t clear_refs_write(struct file *file, const char __user *buf, 472static ssize_t clear_refs_write(struct file *file, const char __user *buf,
469 size_t count, loff_t *ppos) 473 size_t count, loff_t *ppos)
470{ 474{
@@ -472,13 +476,15 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
472 char buffer[PROC_NUMBUF], *end; 476 char buffer[PROC_NUMBUF], *end;
473 struct mm_struct *mm; 477 struct mm_struct *mm;
474 struct vm_area_struct *vma; 478 struct vm_area_struct *vma;
479 int type;
475 480
476 memset(buffer, 0, sizeof(buffer)); 481 memset(buffer, 0, sizeof(buffer));
477 if (count > sizeof(buffer) - 1) 482 if (count > sizeof(buffer) - 1)
478 count = sizeof(buffer) - 1; 483 count = sizeof(buffer) - 1;
479 if (copy_from_user(buffer, buf, count)) 484 if (copy_from_user(buffer, buf, count))
480 return -EFAULT; 485 return -EFAULT;
481 if (!simple_strtol(buffer, &end, 0)) 486 type = simple_strtol(buffer, &end, 0);
487 if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
482 return -EINVAL; 488 return -EINVAL;
483 if (*end == '\n') 489 if (*end == '\n')
484 end++; 490 end++;
@@ -494,9 +500,23 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
494 down_read(&mm->mmap_sem); 500 down_read(&mm->mmap_sem);
495 for (vma = mm->mmap; vma; vma = vma->vm_next) { 501 for (vma = mm->mmap; vma; vma = vma->vm_next) {
496 clear_refs_walk.private = vma; 502 clear_refs_walk.private = vma;
497 if (!is_vm_hugetlb_page(vma)) 503 if (is_vm_hugetlb_page(vma))
498 walk_page_range(vma->vm_start, vma->vm_end, 504 continue;
499 &clear_refs_walk); 505 /*
506 * Writing 1 to /proc/pid/clear_refs affects all pages.
507 *
508 * Writing 2 to /proc/pid/clear_refs only affects
509 * Anonymous pages.
510 *
511 * Writing 3 to /proc/pid/clear_refs only affects file
512 * mapped pages.
513 */
514 if (type == CLEAR_REFS_ANON && vma->vm_file)
515 continue;
516 if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
517 continue;
518 walk_page_range(vma->vm_start, vma->vm_end,
519 &clear_refs_walk);
500 } 520 }
501 flush_tlb_mm(mm); 521 flush_tlb_mm(mm);
502 up_read(&mm->mmap_sem); 522 up_read(&mm->mmap_sem);