From 398499d5f3613c47f2143b8c54a04efb5d7a6da9 Mon Sep 17 00:00:00 2001 From: "Moussa A. Ba" Date: Mon, 21 Sep 2009 17:02:29 -0700 Subject: [PATCH] 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 Signed-off-by: Jared E. Hulbert Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/filesystems/proc.txt | 13 +++++++++++++ fs/proc/task_mmu.c | 28 ++++++++++++++++++++++++---- 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. 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 --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, 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 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, 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 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, 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); -- 2.25.1