mm: smaps: split PSS into components

Report separate components (anon, file, and shmem) for PSS in
smaps_rollup.

This helps understand and tune the memory manager behavior in consumer
devices, particularly mobile devices.  Many of them (e.g.  chromebooks and
Android-based devices) use zram for anon memory, and perform disk reads
for discarded file pages.  The difference in latency is large (e.g.
reading a single page from SSD is 30 times slower than decompressing a
zram page on one popular device), thus it is useful to know how much of
the PSS is anon vs.  file.

All the information is already present in /proc/pid/smaps, but much more
expensive to obtain because of the large size of that procfs entry.

This patch also removes a small code duplication in smaps_account, which
would have gotten worse otherwise.

Also updated Documentation/filesystems/proc.txt (the smaps section was a
bit stale, and I added a smaps_rollup section) and
Documentation/ABI/testing/procfs-smaps_rollup.

[semenzato@chromium.org: v5]
  Link: http://lkml.kernel.org/r/20190626234333.44608-1-semenzato@chromium.org
Link: http://lkml.kernel.org/r/20190626180429.174569-1-semenzato@chromium.org
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Acked-by: Yu Zhao <yuzhao@chromium.org>
Cc: Sonny Rao <sonnyrao@chromium.org>
Cc: Yu Zhao <yuzhao@chromium.org>
Cc: Brian Geffon <bgeffon@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 62 insertions, 30 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7f84d1477b5b..dedca3da428a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -421,17 +421,53 @@ struct mem_size_stats {
 	unsigned long shared_hugetlb;
 	unsigned long private_hugetlb;
 	u64 pss;
+	u64 pss_anon;
+	u64 pss_file;
+	u64 pss_shmem;
 	u64 pss_locked;
 	u64 swap_pss;
 	bool check_shmem_swap;
 };
 
+static void smaps_page_accumulate(struct mem_size_stats *mss,
+		struct page *page, unsigned long size, unsigned long pss,
+		bool dirty, bool locked, bool private)
+{
+	mss->pss += pss;
+
+	if (PageAnon(page))
+		mss->pss_anon += pss;
+	else if (PageSwapBacked(page))
+		mss->pss_shmem += pss;
+	else
+		mss->pss_file += pss;
+
+	if (locked)
+		mss->pss_locked += pss;
+
+	if (dirty || PageDirty(page)) {
+		if (private)
+			mss->private_dirty += size;
+		else
+			mss->shared_dirty += size;
+	} else {
+		if (private)
+			mss->private_clean += size;
+		else
+			mss->shared_clean += size;
+	}
+}
+
 static void smaps_account(struct mem_size_stats *mss, struct page *page,
 		bool compound, bool young, bool dirty, bool locked)
 {
 	int i, nr = compound ? 1 << compound_order(page) : 1;
 	unsigned long size = nr * PAGE_SIZE;
 
+	/*
+	 * First accumulate quantities that depend only on |size| and the type
+	 * of the compound page.
+	 */
 	if (PageAnon(page)) {
 		mss->anonymous += size;
 		if (!PageSwapBacked(page) && !dirty && !PageDirty(page))
@@ -444,42 +480,25 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 		mss->referenced += size;
 
 	/*
+	 * Then accumulate quantities that may depend on sharing, or that may
+	 * differ page-by-page.
+	 *
 	 * page_count(page) == 1 guarantees the page is mapped exactly once.
 	 * If any subpage of the compound page mapped with PTE it would elevate
 	 * page_count().
 	 */
 	if (page_count(page) == 1) {
-		if (dirty || PageDirty(page))
-			mss->private_dirty += size;
-		else
-			mss->private_clean += size;
-		mss->pss += (u64)size << PSS_SHIFT;
-		if (locked)
-			mss->pss_locked += (u64)size << PSS_SHIFT;
+		smaps_page_accumulate(mss, page, size, size << PSS_SHIFT, dirty,
+			locked, true);
 		return;
 	}
-
 	for (i = 0; i < nr; i++, page++) {
 		int mapcount = page_mapcount(page);
-		unsigned long pss = (PAGE_SIZE << PSS_SHIFT);
-
-		if (mapcount >= 2) {
-			if (dirty || PageDirty(page))
-				mss->shared_dirty += PAGE_SIZE;
-			else
-				mss->shared_clean += PAGE_SIZE;
-			mss->pss += pss / mapcount;
-			if (locked)
-				mss->pss_locked += pss / mapcount;
-		} else {
-			if (dirty || PageDirty(page))
-				mss->private_dirty += PAGE_SIZE;
-			else
-				mss->private_clean += PAGE_SIZE;
-			mss->pss += pss;
-			if (locked)
-				mss->pss_locked += pss;
-		}
+		unsigned long pss = PAGE_SIZE << PSS_SHIFT;
+		if (mapcount >= 2)
+			pss /= mapcount;
+		smaps_page_accumulate(mss, page, PAGE_SIZE, pss, dirty, locked,
+				      mapcount < 2);
 	}
 }
 
@@ -758,10 +777,23 @@ static void smap_gather_stats(struct vm_area_struct *vma,
 		seq_put_decimal_ull_width(m, str, (val) >> 10, 8)
 
 /* Show the contents common for smaps and smaps_rollup */
-static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss)
+static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss,
+	bool rollup_mode)
 {
 	SEQ_PUT_DEC("Rss:            ", mss->resident);
 	SEQ_PUT_DEC(" kB\nPss:            ", mss->pss >> PSS_SHIFT);
+	if (rollup_mode) {
+		/*
+		 * These are meaningful only for smaps_rollup, otherwise two of
+		 * them are zero, and the other one is the same as Pss.
+		 */
+		SEQ_PUT_DEC(" kB\nPss_Anon:       ",
+			mss->pss_anon >> PSS_SHIFT);
+		SEQ_PUT_DEC(" kB\nPss_File:       ",
+			mss->pss_file >> PSS_SHIFT);
+		SEQ_PUT_DEC(" kB\nPss_Shmem:      ",
+			mss->pss_shmem >> PSS_SHIFT);
+	}
 	SEQ_PUT_DEC(" kB\nShared_Clean:   ", mss->shared_clean);
 	SEQ_PUT_DEC(" kB\nShared_Dirty:   ", mss->shared_dirty);
 	SEQ_PUT_DEC(" kB\nPrivate_Clean:  ", mss->private_clean);
@@ -798,7 +830,7 @@ static int show_smap(struct seq_file *m, void *v)
 	SEQ_PUT_DEC(" kB\nMMUPageSize:    ", vma_mmu_pagesize(vma));
 	seq_puts(m, " kB\n");
 
-	__show_smap(m, &mss);
+	__show_smap(m, &mss, false);
 
 	seq_printf(m, "THPeligible:    %d\n", transparent_hugepage_enabled(vma));
 
@@ -848,7 +880,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
 	seq_pad(m, ' ');
 	seq_puts(m, "[rollup]\n");
 
-	__show_smap(m, &mss);
+	__show_smap(m, &mss, true);
 
 	release_task_mempolicy(priv);
 	up_read(&mm->mmap_sem);