lkml.org 
[lkml]   [2007]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[patch 3/3 take2] smaps: add clear_refs file to clear reference
    Adds an additional file to /proc/pid: clear_refs.  When any non-zero
    number is written to this file, all the PG_referenced flags and
    PAGE_ACCESSED (meaning the page has been accessed) are cleared within each
    VMA for the corresponding task.

    It is now possible to measure 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 time interval later.

    The /proc/pid/clear_refs file is only writable by the user who owns the
    task.

    Cc: Hugh Dickins <hugh@veritas.com>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: Christoph Lameter <clameter@sgi.com>
    Signed-off-by: David Rientjes <rientjes@google.com>
    ---
    fs/proc/base.c | 31 +++++++++++++++++++++++++++++++
    fs/proc/task_mmu.c | 37 +++++++++++++++++++++++++++++++++++++
    include/linux/proc_fs.h | 1 +
    3 files changed, 69 insertions(+), 0 deletions(-)

    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index 1a979ea..b50315f 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -715,6 +715,35 @@ static 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;
    +
    + 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;
    + clear_refs_smap(task->mm->mmap);
    + 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,
    @@ -1856,6 +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
    @@ -2137,6 +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 50bd004..b689a92 100644
    --- a/fs/proc/task_mmu.c
    +++ b/fs/proc/task_mmu.c
    @@ -322,6 +322,27 @@ static void smaps_pte_func(struct pte_walker *walker, pte_t *pte,
    }

    /*
    + * Called for each PTE in the struct pte_walker address range. For all normal,
    + * present pages, we clear their referenced bits.
    + */
    +static void clear_refs_pte_func(struct pte_walker *walker, pte_t *pte,
    + unsigned long addr)
    +{
    + struct page *page;
    + pte_t ptent;
    +
    + ptent = *pte;
    + if (!pte_present(ptent))
    + return;
    +
    + page = vm_normal_page(walker->vma, addr, ptent);
    + if (!page)
    + return;
    + pte_mkold(ptent);
    + ClearPageReferenced(page);
    +}
    +
    +/*
    * Displays the smap for the process. smaps_pte_func() is called for each PTE
    * in the range from vma->vm_start to vma->vm_end.
    */
    @@ -343,6 +364,22 @@ static int show_smap(struct seq_file *m, void *v)
    return show_map_internal(m, v, &mss);
    }

    +void clear_refs_smap(struct vm_area_struct *vma)
    +{
    + for (; vma; vma = vma->vm_next) {
    + struct pte_walker walker = {
    + .vma = vma,
    + .start = vma->vm_start,
    + .end = vma->vm_end,
    + .private = NULL,
    + .func = clear_refs_pte_func,
    + };
    +
    + if (vma->vm_mm && !is_vm_hugetlb_page(vma))
    + walk_pgds(&walker);
    + };
    +}
    +
    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 87dec8f..f3d426b 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 vm_area_struct *);

    extern struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
    struct proc_dir_entry *parent);
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/
    \
     
     \ /
      Last update: 2007-02-07 07:21    [W:2.146 / U:0.332 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site