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Subject[PATCH v4 7/7] Prevent activation of page in madvise_dontneed
Date
Now zap_pte_range alwayas activates pages which are pte_young &&
!VM_SequentialReadHint(vma). But in case of calling MADV_DONTNEED,
it's unnecessary since the page wouldn't use any more.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Hugh Dickins <hughd@google.com>

Changelog since v3:
- Change variable name - suggested by Johannes
- Union ignore_references with zap_details - suggested by Hugh

Changelog since v2:
- remove unnecessary description

Changelog since v1:
- change word from promote to activate
- add activate argument to zap_pte_range and family function
---
include/linux/mm.h | 4 +++-
mm/madvise.c | 6 +++---
mm/memory.c | 5 ++++-
3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6522ae4..e57190f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -771,12 +771,14 @@ struct zap_details {
pgoff_t last_index; /* Highest page->index to unmap */
spinlock_t *i_mmap_lock; /* For unmap_mapping_range: */
unsigned long truncate_count; /* Compare vm_truncate_count */
+ bool ignore_references; /* For page activation */
};

#define __ZAP_DETAILS_INITIALIZER(name) \
{ .nonlinear_vma = NULL \
, .check_mapping = NULL \
- , .i_mmap_lock = NULL }
+ , .i_mmap_lock = NULL \
+ , .ignore_references = false }

#define DEFINE_ZAP_DETAILS(name) \
struct zap_details name = __ZAP_DETAILS_INITIALIZER(name)
diff --git a/mm/madvise.c b/mm/madvise.c
index bfa17aa..8e7aba3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -163,6 +163,7 @@ static long madvise_dontneed(struct vm_area_struct * vma,
unsigned long start, unsigned long end)
{
DEFINE_ZAP_DETAILS(details);
+ details.ignore_references = true;

*prev = vma;
if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
@@ -173,10 +174,9 @@ static long madvise_dontneed(struct vm_area_struct * vma,
details.last_index = ULONG_MAX;

zap_page_range(vma, start, end - start, &details);
- } else {
-
+ } else
zap_page_range(vma, start, end - start, &details);
- }
+
return 0;
}

diff --git a/mm/memory.c b/mm/memory.c
index c0879bb..44d87e1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -897,6 +897,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
pte_t *pte;
spinlock_t *ptl;
int rss[NR_MM_COUNTERS];
+ bool ignore_references = details->ignore_references;

init_rss_vec(rss);

@@ -952,7 +953,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
if (pte_dirty(ptent))
set_page_dirty(page);
if (pte_young(ptent) &&
- likely(!VM_SequentialReadHint(vma)))
+ likely(!VM_SequentialReadHint(vma)) &&
+ !ignore_references)
mark_page_accessed(page);
rss[MM_FILEPAGES]--;
}
@@ -1218,6 +1220,7 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size)
{
DEFINE_ZAP_DETAILS(details);
+ details.ignore_references = true;
if (address < vma->vm_start || address + size > vma->vm_end ||
!(vma->vm_flags & VM_PFNMAP))
return -1;
--
1.7.0.4


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