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    Subject[PATCH 1/11] maps3: add proportional set size accounting in smaps
    Date
    From: Fengguang Wu <wfg@mail.ustc.edu.cn>

    The "proportional set size" (PSS) of a process is the count of pages it has
    in memory, where each page is divided by the number of processes sharing
    it. So if a process has 1000 pages all to itself, and 1000 shared with one
    other process, its PSS will be 1500.

    - lwn.net: "ELC: How much memory are applications really using?"

    The PSS proposed by Matt Mackall is a very nice metic for measuring an
    process's memory footprint. So collect and export it via
    /proc/<pid>/smaps.

    Matt Mackall's pagemap/kpagemap and John Berthels's exmap can also do the
    job. They are comprehensive tools. But for PSS, let's do it in the simple
    way.

    Cc: John Berthels <jjberthels@gmail.com>
    Cc: Bernardo Innocenti <bernie@codewiz.org>
    Cc: Padraig Brady <P@draigBrady.com>
    Cc: Denys Vlasenko <vda.linux@googlemail.com>
    Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
    Signed-off-by: Matt Mackall <mpm@selenic.com>
    Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
    Cc: Hugh Dickins <hugh@veritas.com>
    ---

    fs/proc/task_mmu.c | 29 ++++++++++++++++++++++++++++-
    1 files changed, 28 insertions(+), 1 deletion(-)

    Index: l/fs/proc/task_mmu.c
    ===================================================================
    --- l.orig/fs/proc/task_mmu.c 2007-10-14 13:35:31.000000000 -0500
    +++ l/fs/proc/task_mmu.c 2007-10-14 13:36:56.000000000 -0500
    @@ -122,6 +122,27 @@ struct mem_size_stats
    unsigned long private_clean;
    unsigned long private_dirty;
    unsigned long referenced;
    +
    + /*
    + * Proportional Set Size(PSS): my share of RSS.
    + *
    + * PSS of a process is the count of pages it has in memory, where each
    + * page is divided by the number of processes sharing it. So if a
    + * process has 1000 pages all to itself, and 1000 shared with one other
    + * process, its PSS will be 1500. - Matt Mackall, lwn.net
    + */
    + u64 pss;
    + /*
    + * To keep (accumulated) division errors low, we adopt 64bit pss and
    + * use some low bits for division errors. So (pss >> PSS_DIV_BITS)
    + * would be the real byte count.
    + *
    + * A shift of 12 before division means(assuming 4K page size):
    + * - 1M 3-user-pages add up to 8KB errors;
    + * - supports mapcount up to 2^24, or 16M;
    + * - supports PSS up to 2^52 bytes, or 4PB.
    + */
    +#define PSS_DIV_BITS 12
    };

    struct pmd_walker {
    @@ -195,6 +216,7 @@ static int show_map_internal(struct seq_
    seq_printf(m,
    "Size: %8lu kB\n"
    "Rss: %8lu kB\n"
    + "Pss: %8lu kB\n"
    "Shared_Clean: %8lu kB\n"
    "Shared_Dirty: %8lu kB\n"
    "Private_Clean: %8lu kB\n"
    @@ -202,6 +224,7 @@ static int show_map_internal(struct seq_
    "Referenced: %8lu kB\n",
    (vma->vm_end - vma->vm_start) >> 10,
    mss->resident >> 10,
    + (unsigned long)(mss.pss >> (10 + PSS_DIV_BITS)),
    mss->shared_clean >> 10,
    mss->shared_dirty >> 10,
    mss->private_clean >> 10,
    @@ -226,6 +249,7 @@ static void smaps_pte_range(struct vm_ar
    pte_t *pte, ptent;
    spinlock_t *ptl;
    struct page *page;
    + int mapcount;

    pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
    for (; addr != end; pte++, addr += PAGE_SIZE) {
    @@ -242,16 +266,19 @@ static void smaps_pte_range(struct vm_ar
    /* Accumulate the size in pages that have been accessed. */
    if (pte_young(ptent) || PageReferenced(page))
    mss->referenced += PAGE_SIZE;
    - if (page_mapcount(page) >= 2) {
    + mapcount = page_mapcount(page);
    + if (mapcount >= 2) {
    if (pte_dirty(ptent))
    mss->shared_dirty += PAGE_SIZE;
    else
    mss->shared_clean += PAGE_SIZE;
    + mss->pss += (PAGE_SIZE << PSS_DIV_BITS) / mapcount;
    } else {
    if (pte_dirty(ptent))
    mss->private_dirty += PAGE_SIZE;
    else
    mss->private_clean += PAGE_SIZE;
    + mss->pss += (PAGE_SIZE << PSS_DIV_BITS);
    }
    }
    pte_unmap_unlock(pte - 1, ptl);
    -
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