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Subject[PATCH 14/21] mm: tlb_finish_mmu forget rss
zap_pte_range has been counting the pages it frees in tlb->freed, then
tlb_finish_mmu has used that to update the mm's rss. That got stranger
when I added anon_rss, yet updated it by a different route; and stranger
when rss and anon_rss became mm_counters with special access macros.
And it would no longer be viable if we're relying on page_table_lock to
stabilize the mm_counter, but calling tlb_finish_mmu outside that lock.

Remove the mmu_gather's freed field, let tlb_finish_mmu stick to its own
business, just decrement the rss mm_counter in zap_pte_range (yes, there
was some point to batching the update, and a subsequent patch restores
that). And forget the anal paranoia of first reading the counter to
avoid going negative - if rss does go negative, just fix that bug.

Remove the mmu_gather's flushes and avoided_flushes from arm and arm26:
no use was being made of them. But arm26 alone was actually using the
freed, in the way some others use need_flush: give it a need_flush.
arm26 seems to prefer spaces to tabs here: respect that.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---

include/asm-arm/tlb.h | 15 +--------------
include/asm-arm26/tlb.h | 35 +++++++++++++----------------------
include/asm-generic/tlb.h | 9 ---------
include/asm-ia64/tlb.h | 9 ---------
include/asm-sparc64/tlb.h | 14 ++------------
mm/memory.c | 2 +-
6 files changed, 17 insertions(+), 67 deletions(-)

--- mm13/include/asm-arm/tlb.h 2005-09-24 19:29:10.000000000 +0100
+++ mm14/include/asm-arm/tlb.h 2005-09-24 19:29:25.000000000 +0100
@@ -27,11 +27,7 @@
*/
struct mmu_gather {
struct mm_struct *mm;
- unsigned int freed;
unsigned int fullmm;
-
- unsigned int flushes;
- unsigned int avoided_flushes;
};

DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
@@ -42,7 +38,6 @@ tlb_gather_mmu(struct mm_struct *mm, uns
struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);

tlb->mm = mm;
- tlb->freed = 0;
tlb->fullmm = full_mm_flush;

return tlb;
@@ -51,16 +46,8 @@ tlb_gather_mmu(struct mm_struct *mm, uns
static inline void
tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
- struct mm_struct *mm = tlb->mm;
- unsigned long freed = tlb->freed;
- int rss = get_mm_counter(mm, rss);
-
- if (rss < freed)
- freed = rss;
- add_mm_counter(mm, rss, -freed);
-
if (tlb->fullmm)
- flush_tlb_mm(mm);
+ flush_tlb_mm(tlb->mm);

/* keep the page table cache within bounds */
check_pgt_cache();
--- mm13/include/asm-arm26/tlb.h 2005-09-24 19:29:10.000000000 +0100
+++ mm14/include/asm-arm26/tlb.h 2005-09-24 19:29:25.000000000 +0100
@@ -10,11 +10,8 @@
*/
struct mmu_gather {
struct mm_struct *mm;
- unsigned int freed;
- unsigned int fullmm;
-
- unsigned int flushes;
- unsigned int avoided_flushes;
+ unsigned int need_flush;
+ unsigned int fullmm;
};

DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
@@ -25,8 +22,8 @@ tlb_gather_mmu(struct mm_struct *mm, uns
struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);

tlb->mm = mm;
- tlb->freed = 0;
- tlb->fullmm = full_mm_flush;
+ tlb->need_flush = 0;
+ tlb->fullmm = full_mm_flush;

return tlb;
}
@@ -34,20 +31,8 @@ tlb_gather_mmu(struct mm_struct *mm, uns
static inline void
tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
- struct mm_struct *mm = tlb->mm;
- unsigned long freed = tlb->freed;
- int rss = get_mm_counter(mm, rss);
-
- if (rss < freed)
- freed = rss;
- add_mm_counter(mm, rss, -freed);
-
- if (freed) {
- flush_tlb_mm(mm);
- tlb->flushes++;
- } else {
- tlb->avoided_flushes++;
- }
+ if (tlb->need_flush)
+ flush_tlb_mm(tlb->mm);

/* keep the page table cache within bounds */
check_pgt_cache();
@@ -65,7 +50,13 @@ tlb_finish_mmu(struct mmu_gather *tlb, u
} while (0)
#define tlb_end_vma(tlb,vma) do { } while (0)

-#define tlb_remove_page(tlb,page) free_page_and_swap_cache(page)
+static inline void
+tlb_remove_page(struct mmu_gather *tlb, struct page *page)
+{
+ tlb->need_flush = 1;
+ free_page_and_swap_cache(page);
+}
+
#define pte_free_tlb(tlb,ptep) pte_free(ptep)
#define pmd_free_tlb(tlb,pmdp) pmd_free(pmdp)

--- mm13/include/asm-generic/tlb.h 2005-09-24 19:29:10.000000000 +0100
+++ mm14/include/asm-generic/tlb.h 2005-09-24 19:29:25.000000000 +0100
@@ -42,7 +42,6 @@ struct mmu_gather {
unsigned int nr; /* set to ~0U means fast mode */
unsigned int need_flush;/* Really unmapped some ptes? */
unsigned int fullmm; /* non-zero means full mm flush */
- unsigned long freed;
struct page * pages[FREE_PTE_NR];
};

@@ -63,7 +62,6 @@ tlb_gather_mmu(struct mm_struct *mm, uns
tlb->nr = num_online_cpus() > 1 ? 0U : ~0U;

tlb->fullmm = full_mm_flush;
- tlb->freed = 0;

return tlb;
}
@@ -88,13 +86,6 @@ tlb_flush_mmu(struct mmu_gather *tlb, un
static inline void
tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
- int freed = tlb->freed;
- struct mm_struct *mm = tlb->mm;
- int rss = get_mm_counter(mm, rss);
-
- if (rss < freed)
- freed = rss;
- add_mm_counter(mm, rss, -freed);
tlb_flush_mmu(tlb, start, end);

/* keep the page table cache within bounds */
--- mm13/include/asm-ia64/tlb.h 2005-09-24 19:29:10.000000000 +0100
+++ mm14/include/asm-ia64/tlb.h 2005-09-24 19:29:25.000000000 +0100
@@ -60,7 +60,6 @@ struct mmu_gather {
unsigned int nr; /* == ~0U => fast mode */
unsigned char fullmm; /* non-zero means full mm flush */
unsigned char need_flush; /* really unmapped some PTEs? */
- unsigned long freed; /* number of pages freed */
unsigned long start_addr;
unsigned long end_addr;
struct page *pages[FREE_PTE_NR];
@@ -147,7 +146,6 @@ tlb_gather_mmu (struct mm_struct *mm, un
*/
tlb->nr = (num_online_cpus() == 1) ? ~0U : 0;
tlb->fullmm = full_mm_flush;
- tlb->freed = 0;
tlb->start_addr = ~0UL;
return tlb;
}
@@ -159,13 +157,6 @@ tlb_gather_mmu (struct mm_struct *mm, un
static inline void
tlb_finish_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
- unsigned long freed = tlb->freed;
- struct mm_struct *mm = tlb->mm;
- unsigned long rss = get_mm_counter(mm, rss);
-
- if (rss < freed)
- freed = rss;
- add_mm_counter(mm, rss, -freed);
/*
* Note: tlb->nr may be 0 at this point, so we can't rely on tlb->start_addr and
* tlb->end_addr.
--- mm13/include/asm-sparc64/tlb.h 2005-09-24 19:29:10.000000000 +0100
+++ mm14/include/asm-sparc64/tlb.h 2005-09-24 19:29:25.000000000 +0100
@@ -27,7 +27,6 @@ struct mmu_gather {
unsigned int need_flush;
unsigned int fullmm;
unsigned int tlb_nr;
- unsigned long freed;
unsigned long vaddrs[TLB_BATCH_NR];
struct page *pages[FREE_PTE_NR];
};
@@ -51,7 +50,6 @@ static inline struct mmu_gather *tlb_gat
mp->mm = mm;
mp->pages_nr = num_online_cpus() > 1 ? 0U : ~0U;
mp->fullmm = full_mm_flush;
- mp->freed = 0;

return mp;
}
@@ -78,19 +76,11 @@ extern void smp_flush_tlb_mm(struct mm_s

static inline void tlb_finish_mmu(struct mmu_gather *mp, unsigned long start, unsigned long end)
{
- unsigned long freed = mp->freed;
- struct mm_struct *mm = mp->mm;
- unsigned long rss = get_mm_counter(mm, rss);
-
- if (rss < freed)
- freed = rss;
- add_mm_counter(mm, rss, -freed);
-
tlb_flush_mmu(mp);

if (mp->fullmm) {
- if (CTX_VALID(mm->context))
- do_flush_tlb_mm(mm);
+ if (CTX_VALID(mp->mm->context))
+ do_flush_tlb_mm(mp->mm);
mp->fullmm = 0;
} else
flush_tlb_pending();
--- mm13/mm/memory.c 2005-09-24 19:29:10.000000000 +0100
+++ mm14/mm/memory.c 2005-09-24 19:29:25.000000000 +0100
@@ -582,7 +582,7 @@ static void zap_pte_range(struct mmu_gat
if (pte_young(ptent))
mark_page_accessed(page);
}
- tlb->freed++;
+ dec_mm_counter(tlb->mm, rss);
page_remove_rmap(page);
tlb_remove_page(tlb, page);
continue;
-
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