Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b813e931b4c8235bb42e301096ea97dbdee3e8fe
Commit:     b813e931b4c8235bb42e301096ea97dbdee3e8fe
Parent:     f79f177c25016647cc92ffac8afa7cb96ce47011
Author:     David Rientjes <[EMAIL PROTECTED]>
AuthorDate: Sun May 6 14:49:24 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon May 7 12:12:52 2007 -0700

    smaps: add clear_refs file to clear reference
    
    Adds /proc/pid/clear_refs.  When any non-zero number is written to this 
file,
    pte_mkold() and ClearPageReferenced() is called for each pte and its
    corresponding page, respectively, in that task's VMAs.  This file is only
    writable by the user who owns the task.
    
    It is now possible to measure _approximately_ how much memory a task is 
using
    by clearing the reference bits with
    
        echo 1 > /proc/pid/clear_refs
    
    and checking the reference count for each VMA from the /proc/pid/smaps 
output
    at a measured time interval.  For example, to observe the approximate change
    in memory footprint for a task, write a script that clears the references
    (echo 1 > /proc/pid/clear_refs), sleeps, and then greps for Pgs_Referenced 
and
    extracts the size in kB.  Add the sizes for each VMA together for the total
    referenced footprint.  Moments later, repeat the process and observe the
    difference.
    
    For example, using an efficient Mozilla:
    
        accumulated time                referenced memory
        ----------------                -----------------
                 0 s                             408 kB
                 1 s                             408 kB
                 2 s                             556 kB
                 3 s                            1028 kB
                 4 s                             872 kB
                 5 s                            1956 kB
                 6 s                             416 kB
                 7 s                            1560 kB
                 8 s                            2336 kB
                 9 s                            1044 kB
                10 s                             416 kB
    
    This is a valuable tool to get an approximate measurement of the memory
    footprint for a task.
    
    Cc: Hugh Dickins <[EMAIL PROTECTED]>
    Cc: Paul Mundt <[EMAIL PROTECTED]>
    Cc: Christoph Lameter <[EMAIL PROTECTED]>
    Signed-off-by: David Rientjes <[EMAIL PROTECTED]>
    [EMAIL PROTECTED]: build fixes]
    [EMAIL PROTECTED]: rename for_each_pmd]
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 Documentation/filesystems/proc.txt |   31 +++++++-------
 fs/proc/base.c                     |   36 ++++++++++++++++
 fs/proc/task_mmu.c                 |   79 ++++++++++++++++++++++++++++-------
 include/linux/proc_fs.h            |    1 +
 4 files changed, 116 insertions(+), 31 deletions(-)

diff --git a/Documentation/filesystems/proc.txt 
b/Documentation/filesystems/proc.txt
index 7aaf09b..3f4b226 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -122,21 +122,22 @@ subdirectory has the entries listed in Table 1-1.
 
 Table 1-1: Process specific entries in /proc 
 ..............................................................................
- File    Content                                        
- cmdline Command line arguments                         
- cpu    Current and last cpu in which it was executed          (2.4)(smp)
- cwd    Link to the current working directory
- environ Values of environment variables      
- exe    Link to the executable of this process
- fd      Directory, which contains all file descriptors 
- maps   Memory maps to executables and library files           (2.4)
- mem     Memory held by this process                    
- root   Link to the root directory of this process
- stat    Process status                                 
- statm   Process memory status information              
- status  Process status in human readable form          
- wchan   If CONFIG_KALLSYMS is set, a pre-decoded wchan
- smaps  Extension based on maps, presenting the rss size for each mapped file
+ File          Content
+ clear_refs    Clears page referenced bits shown in smaps output
+ cmdline       Command line arguments
+ cpu           Current and last cpu in which it was executed   (2.4)(smp)
+ cwd           Link to the current working directory
+ environ       Values of environment variables
+ exe           Link to the executable of this process
+ fd            Directory, which contains all file descriptors
+ maps          Memory maps to executables and library files    (2.4)
+ mem           Memory held by this process
+ root          Link to the root directory of this process
+ stat          Process status
+ statm         Process memory status information
+ status                Process status in human readable form
+ wchan         If CONFIG_KALLSYMS is set, a pre-decoded wchan
+ smaps         Extension based on maps, the rss size for each mapped file
 ..............................................................................
 
 For example, to get the status information of a process, all you have to do is
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 989af5e..ec158dd 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -715,6 +715,40 @@ static const struct file_operations 
proc_oom_adjust_operations = {
        .write          = oom_adjust_write,
 };
 
+static ssize_t clear_refs_write(struct file *file, const char __user *buf,
+                               size_t count, loff_t *ppos)
+{
+       struct task_struct *task;
+       char buffer[PROC_NUMBUF], *end;
+       struct mm_struct *mm;
+
+       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))
+               return -EINVAL;
+       if (*end == '\n')
+               end++;
+       task = get_proc_task(file->f_path.dentry->d_inode);
+       if (!task)
+               return -ESRCH;
+       mm = get_task_mm(task);
+       if (mm) {
+               clear_refs_smap(mm);
+               mmput(mm);
+       }
+       put_task_struct(task);
+       if (end - buffer == 0)
+               return -EIO;
+       return end - buffer;
+}
+
+static struct file_operations proc_clear_refs_operations = {
+       .write          = clear_refs_write,
+};
+
 #ifdef CONFIG_AUDITSYSCALL
 #define TMPBUFLEN 21
 static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
@@ -1851,6 +1885,7 @@ static struct pid_entry tgid_base_stuff[] = {
        REG("mounts",     S_IRUGO, mounts),
        REG("mountstats", S_IRUSR, mountstats),
 #ifdef CONFIG_MMU
+       REG("clear_refs", S_IWUSR, clear_refs),
        REG("smaps",      S_IRUGO, smaps),
 #endif
 #ifdef CONFIG_SECURITY
@@ -2132,6 +2167,7 @@ static struct pid_entry tid_base_stuff[] = {
        LNK("exe",       exe),
        REG("mounts",    S_IRUGO, mounts),
 #ifdef CONFIG_MMU
+       REG("clear_refs", S_IWUSR, clear_refs),
        REG("smaps",     S_IRUGO, smaps),
 #endif
 #ifdef CONFIG_SECURITY
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 199088e..4008c06 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -195,7 +195,7 @@ static int show_map_internal(struct seq_file *m, void *v, 
struct mem_size_stats
                           "Shared_Dirty:   %8lu kB\n"
                           "Private_Clean:  %8lu kB\n"
                           "Private_Dirty:  %8lu kB\n"
-                          "Pgs_Referenced: %8lu kB\n",
+                          "Referenced:     %8lu kB\n",
                           (vma->vm_end - vma->vm_start) >> 10,
                           mss->resident >> 10,
                           mss->shared_clean  >> 10,
@@ -214,9 +214,9 @@ static int show_map(struct seq_file *m, void *v)
        return show_map_internal(m, v, NULL);
 }
 
-static void smaps_one_pmd(struct vm_area_struct *vma, pmd_t *pmd,
-                         unsigned long addr, unsigned long end,
-                         void *private)
+static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
+                           unsigned long addr, unsigned long end,
+                           void *private)
 {
        struct mem_size_stats *mss = private;
        pte_t *pte, ptent;
@@ -254,8 +254,34 @@ static void smaps_one_pmd(struct vm_area_struct *vma, 
pmd_t *pmd,
        cond_resched();
 }
 
-static inline void for_each_pmd_in_pud(struct pmd_walker *walker, pud_t *pud,
-                                      unsigned long addr, unsigned long end)
+static void clear_refs_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
+                                unsigned long addr, unsigned long end,
+                                void *private)
+{
+       pte_t *pte, ptent;
+       spinlock_t *ptl;
+       struct page *page;
+
+       pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+       for (; addr != end; pte++, addr += PAGE_SIZE) {
+               ptent = *pte;
+               if (!pte_present(ptent))
+                       continue;
+
+               page = vm_normal_page(vma, addr, ptent);
+               if (!page)
+                       continue;
+
+               /* Clear accessed and referenced bits. */
+               ptep_test_and_clear_young(vma, addr, pte);
+               ClearPageReferenced(page);
+       }
+       pte_unmap_unlock(pte - 1, ptl);
+       cond_resched();
+}
+
+static inline void walk_pmd_range(struct pmd_walker *walker, pud_t *pud,
+                                 unsigned long addr, unsigned long end)
 {
        pmd_t *pmd;
        unsigned long next;
@@ -269,8 +295,8 @@ static inline void for_each_pmd_in_pud(struct pmd_walker 
*walker, pud_t *pud,
        }
 }
 
-static inline void for_each_pud_in_pgd(struct pmd_walker *walker, pgd_t *pgd,
-                                      unsigned long addr, unsigned long end)
+static inline void walk_pud_range(struct pmd_walker *walker, pgd_t *pgd,
+                                 unsigned long addr, unsigned long end)
 {
        pud_t *pud;
        unsigned long next;
@@ -280,15 +306,24 @@ static inline void for_each_pud_in_pgd(struct pmd_walker 
*walker, pgd_t *pgd,
                next = pud_addr_end(addr, end);
                if (pud_none_or_clear_bad(pud))
                        continue;
-               for_each_pmd_in_pud(walker, pud, addr, next);
+               walk_pmd_range(walker, pud, addr, next);
        }
 }
 
-static inline void for_each_pmd(struct vm_area_struct *vma,
-                               void (*action)(struct vm_area_struct *, pmd_t *,
-                                              unsigned long, unsigned long,
-                                              void *),
-                               void *private)
+/*
+ * walk_page_range - walk the page tables of a VMA with a callback
+ * @vma - VMA to walk
+ * @action - callback invoked for every bottom-level (PTE) page table
+ * @private - private data passed to the callback function
+ *
+ * Recursively walk the page table for the memory area in a VMA, calling
+ * a callback for every bottom-level (PTE) page table.
+ */
+static inline void walk_page_range(struct vm_area_struct *vma,
+                                  void (*action)(struct vm_area_struct *,
+                                                 pmd_t *, unsigned long,
+                                                 unsigned long, void *),
+                                  void *private)
 {
        unsigned long addr = vma->vm_start;
        unsigned long end = vma->vm_end;
@@ -305,7 +340,7 @@ static inline void for_each_pmd(struct vm_area_struct *vma,
                next = pgd_addr_end(addr, end);
                if (pgd_none_or_clear_bad(pgd))
                        continue;
-               for_each_pud_in_pgd(&walker, pgd, addr, next);
+               walk_pud_range(&walker, pgd, addr, next);
        }
 }
 
@@ -316,10 +351,22 @@ static int show_smap(struct seq_file *m, void *v)
 
        memset(&mss, 0, sizeof mss);
        if (vma->vm_mm && !is_vm_hugetlb_page(vma))
-               for_each_pmd(vma, smaps_one_pmd, &mss);
+               walk_page_range(vma, smaps_pte_range, &mss);
        return show_map_internal(m, v, &mss);
 }
 
+void clear_refs_smap(struct mm_struct *mm)
+{
+       struct vm_area_struct *vma;
+
+       down_read(&mm->mmap_sem);
+       for (vma = mm->mmap; vma; vma = vma->vm_next)
+               if (vma->vm_mm && !is_vm_hugetlb_page(vma))
+                       walk_page_range(vma, clear_refs_pte_range, NULL);
+       flush_tlb_mm(mm);
+       up_read(&mm->mmap_sem);
+}
+
 static void *m_start(struct seq_file *m, loff_t *pos)
 {
        struct proc_maps_private *priv = m->private;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index be4652a..f4f7a63 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -104,6 +104,7 @@ int proc_pid_readdir(struct file * filp, void * dirent, 
filldir_t filldir);
 unsigned long task_vsize(struct mm_struct *);
 int task_statm(struct mm_struct *, int *, int *, int *, int *);
 char *task_mem(struct mm_struct *, char *);
+void clear_refs_smap(struct mm_struct *mm);
 
 extern struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
                                                struct proc_dir_entry *parent);
-
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