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authorFengguang Wu <wfg@mail.ustc.edu.cn>2008-02-04 22:28:56 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 09:44:16 -0800
commitec4dd3eb35759f9fbeb5c1abb01403b2fde64cc9 (patch)
tree0eaf4d91180556df61da6300463d946390ce55fb
parent61d5048f149572434daee0cce5e1374a8a7cf3e8 (diff)
maps4: add proportional set size accounting in smaps
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> Cc: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/task_mmu.c28
1 files changed, 27 insertions, 1 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8043a3eab52..8952ce70315 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -114,6 +114,25 @@ static void pad_len_spaces(struct seq_file *m, int len)
seq_printf(m, "%*c", len, ' ');
}
+/*
+ * 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.
+ *
+ * To keep (accumulated) division errors low, we adopt a 64bit
+ * fixed-point pss counter to minimize division errors. So (pss >>
+ * PSS_SHIFT) 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_SHIFT 12
+
struct mem_size_stats
{
unsigned long resident;
@@ -122,6 +141,7 @@ struct mem_size_stats
unsigned long private_clean;
unsigned long private_dirty;
unsigned long referenced;
+ u64 pss;
};
struct pmd_walker {
@@ -195,6 +215,7 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
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 +223,7 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
"Referenced: %8lu kB\n",
(vma->vm_end - vma->vm_start) >> 10,
mss->resident >> 10,
+ (unsigned long)(mss->pss >> (10 + PSS_SHIFT)),
mss->shared_clean >> 10,
mss->shared_dirty >> 10,
mss->private_clean >> 10,
@@ -226,6 +248,7 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
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 +265,19 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
/* 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_SHIFT) / mapcount;
} else {
if (pte_dirty(ptent))
mss->private_dirty += PAGE_SIZE;
else
mss->private_clean += PAGE_SIZE;
+ mss->pss += (PAGE_SIZE << PSS_SHIFT);
}
}
pte_unmap_unlock(pte - 1, ptl);