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Subject[PATCH 17/21] mm: batch updating mm_counters
tlb_finish_mmu used to batch zap_pte_range's update of mm rss, which may
be worthwhile if the mm is contended, and would reduce atomic operations
if the counts were atomic. Let zap_pte_range now batch its updates to
file_rss and anon_rss, per page-table in case we drop the lock outside;
and copy_pte_range batch them too.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
mm/memory.c | 47 ++++++++++++++++++++++++++++++++---------------
1 files changed, 32 insertions(+), 15 deletions(-)
--- mm16/mm/memory.c 2005-09-24 19:29:53.000000000 +0100
+++ mm17/mm/memory.c 2005-09-24 19:30:07.000000000 +0100
@@ -332,6 +332,16 @@ out:
return pte_offset_kernel(pmd, address);
}

+static inline void add_mm_rss(struct mm_struct *mm, int file_rss, int anon_rss)
+{
+ if (file_rss)
+ add_mm_counter(mm, file_rss, file_rss);
+ if (anon_rss)
+ add_mm_counter(mm, anon_rss, anon_rss);
+}
+
+#define NO_RSS 2 /* Increment neither file_rss nor anon_rss */
+
/*
* copy one vm_area from one task to the other. Assumes the page tables
* already present in the new task to be cleared in the whole range
@@ -341,7 +351,7 @@ out:
* but may be dropped within p[mg]d_alloc() and pte_alloc_map().
*/

-static inline void
+static inline int
copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pte_t *dst_pte, pte_t *src_pte, unsigned long vm_flags,
unsigned long addr)
@@ -349,6 +359,7 @@ copy_one_pte(struct mm_struct *dst_mm, s
pte_t pte = *src_pte;
struct page *page;
unsigned long pfn;
+ int anon = NO_RSS;

/* pte contains position in swap or file, so copy. */
if (unlikely(!pte_present(pte))) {
@@ -361,8 +372,7 @@ copy_one_pte(struct mm_struct *dst_mm, s
spin_unlock(&mmlist_lock);
}
}
- set_pte_at(dst_mm, addr, dst_pte, pte);
- return;
+ goto out_set_pte;
}

pfn = pte_pfn(pte);
@@ -375,10 +385,8 @@ copy_one_pte(struct mm_struct *dst_mm, s
if (pfn_valid(pfn))
page = pfn_to_page(pfn);

- if (!page || PageReserved(page)) {
- set_pte_at(dst_mm, addr, dst_pte, pte);
- return;
- }
+ if (!page || PageReserved(page))
+ goto out_set_pte;

/*
* If it's a COW mapping, write protect it both
@@ -397,12 +405,12 @@ copy_one_pte(struct mm_struct *dst_mm, s
pte = pte_mkclean(pte);
pte = pte_mkold(pte);
get_page(page);
- if (PageAnon(page))
- inc_mm_counter(dst_mm, anon_rss);
- else
- inc_mm_counter(dst_mm, file_rss);
- set_pte_at(dst_mm, addr, dst_pte, pte);
page_dup_rmap(page);
+ anon = !!PageAnon(page);
+
+out_set_pte:
+ set_pte_at(dst_mm, addr, dst_pte, pte);
+ return anon;
}

static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
@@ -412,8 +420,10 @@ static int copy_pte_range(struct mm_stru
pte_t *src_pte, *dst_pte;
unsigned long vm_flags = vma->vm_flags;
int progress = 0;
+ int rss[NO_RSS+1], anon;

again:
+ rss[1] = rss[0] = 0;
dst_pte = pte_alloc_map(dst_mm, dst_pmd, addr);
if (!dst_pte)
return -ENOMEM;
@@ -436,13 +446,16 @@ again:
progress++;
continue;
}
- copy_one_pte(dst_mm, src_mm, dst_pte, src_pte, vm_flags, addr);
+ anon = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
+ vm_flags, addr);
+ rss[anon]++;
progress += 8;
} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
spin_unlock(&src_mm->page_table_lock);

pte_unmap_nested(src_pte - 1);
pte_unmap(dst_pte - 1);
+ add_mm_rss(dst_mm, rss[0], rss[1]);
cond_resched_lock(&dst_mm->page_table_lock);
if (addr != end)
goto again;
@@ -533,6 +546,8 @@ static void zap_pte_range(struct mmu_gat
struct zap_details *details)
{
pte_t *pte;
+ int file_rss = 0;
+ int anon_rss = 0;

pte = pte_offset_map(pmd, addr);
do {
@@ -576,13 +591,13 @@ static void zap_pte_range(struct mmu_gat
set_pte_at(tlb->mm, addr, pte,
pgoff_to_pte(page->index));
if (PageAnon(page))
- dec_mm_counter(tlb->mm, anon_rss);
+ anon_rss++;
else {
if (pte_dirty(ptent))
set_page_dirty(page);
if (pte_young(ptent))
mark_page_accessed(page);
- dec_mm_counter(tlb->mm, file_rss);
+ file_rss++;
}
page_remove_rmap(page);
tlb_remove_page(tlb, page);
@@ -598,6 +613,8 @@ static void zap_pte_range(struct mmu_gat
free_swap_and_cache(pte_to_swp_entry(ptent));
pte_clear_full(tlb->mm, addr, pte, tlb->fullmm);
} while (pte++, addr += PAGE_SIZE, addr != end);
+
+ add_mm_rss(tlb->mm, -file_rss, -anon_rss);
pte_unmap(pte - 1);
}

-
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