Commit ec4dd3eb authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

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: default avatarMatt Mackall <mpm@selenic.com>
Signed-off-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 61d5048f

fs/proc/task_mmu.c

+27 −1
Original line number Diff line number Diff line
@@ -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);

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