The patch titled
Subject: rmap: introduce rmap_walk_locked()
has been added to the -mm tree. Its filename is
rmap-introduce-rmap_walk_locked.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/rmap-introduce-rmap_walk_locked.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/rmap-introduce-rmap_walk_locked.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: rmap: introduce rmap_walk_locked()
This patchset rewrites freeze_page() and unfreeze_page() using
try_to_unmap() and remove_migration_ptes(). Result is much simpler, but
somewhat slower.
Migration 8GiB worth of PMD-mapped THP:
Baseline 20.21 +/- 0.393
Patched 20.73 +/- 0.082
Slowdown 1.03x
It's 3% slower, comparing to 14% in v1. I don't it should be a stopper.
Splitting of PTE-mapped pages slowed more. But this is not a common case.
Migration 8GiB worth of PMD-mapped THP:
Baseline 20.39 +/- 0.225
Patched 22.43 +/- 0.496
Slowdown 1.10x
rmap_walk_locked() is the same as rmap_walk(), but the caller takes care
of the relevant rmap lock.
This is preparation for switching THP splitting from custom rmap walk in
freeze_page()/unfreeze_page() to the generic one.
There is no support for KSM pages for now: not clear which lock is implied.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rmap.h | 1 +
mm/rmap.c | 41 ++++++++++++++++++++++++++++++++---------
2 files changed, 33 insertions(+), 9 deletions(-)
diff -puN include/linux/rmap.h~rmap-introduce-rmap_walk_locked include/linux/rmap.h
--- a/include/linux/rmap.h~rmap-introduce-rmap_walk_locked
+++ a/include/linux/rmap.h
@@ -266,6 +266,7 @@ struct rmap_walk_control {
};
int rmap_walk(struct page *page, struct rmap_walk_control *rwc);
+int rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
#else /* !CONFIG_MMU */
diff -puN mm/rmap.c~rmap-introduce-rmap_walk_locked mm/rmap.c
--- a/mm/rmap.c~rmap-introduce-rmap_walk_locked
+++ a/mm/rmap.c
@@ -1715,14 +1715,21 @@ static struct anon_vma *rmap_walk_anon_l
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
* LOCKED.
*/
-static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
+static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
+ bool locked)
{
struct anon_vma *anon_vma;
pgoff_t pgoff;
struct anon_vma_chain *avc;
int ret = SWAP_AGAIN;
- anon_vma = rmap_walk_anon_lock(page, rwc);
+ if (locked) {
+ anon_vma = page_anon_vma(page);
+ /* anon_vma disappear under us? */
+ VM_BUG_ON_PAGE(!anon_vma, page);
+ } else {
+ anon_vma = rmap_walk_anon_lock(page, rwc);
+ }
if (!anon_vma)
return ret;
@@ -1742,7 +1749,9 @@ static int rmap_walk_anon(struct page *p
if (rwc->done && rwc->done(page))
break;
}
- anon_vma_unlock_read(anon_vma);
+
+ if (!locked)
+ anon_vma_unlock_read(anon_vma);
return ret;
}
@@ -1759,9 +1768,10 @@ static int rmap_walk_anon(struct page *p
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
* LOCKED.
*/
-static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
+static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
+ bool locked)
{
- struct address_space *mapping = page->mapping;
+ struct address_space *mapping = page_mapping(page);
pgoff_t pgoff;
struct vm_area_struct *vma;
int ret = SWAP_AGAIN;
@@ -1778,7 +1788,8 @@ static int rmap_walk_file(struct page *p
return ret;
pgoff = page_to_pgoff(page);
- i_mmap_lock_read(mapping);
+ if (!locked)
+ i_mmap_lock_read(mapping);
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
unsigned long address = vma_address(page, vma);
@@ -1795,7 +1806,8 @@ static int rmap_walk_file(struct page *p
}
done:
- i_mmap_unlock_read(mapping);
+ if (!locked)
+ i_mmap_unlock_read(mapping);
return ret;
}
@@ -1804,9 +1816,20 @@ int rmap_walk(struct page *page, struct
if (unlikely(PageKsm(page)))
return rmap_walk_ksm(page, rwc);
else if (PageAnon(page))
- return rmap_walk_anon(page, rwc);
+ return rmap_walk_anon(page, rwc, false);
+ else
+ return rmap_walk_file(page, rwc, false);
+}
+
+/* Like rmap_walk, but caller holds relevant rmap lock */
+int rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc)
+{
+ /* no ksm support for now */
+ VM_BUG_ON_PAGE(PageKsm(page), page);
+ if (PageAnon(page))
+ return rmap_walk_anon(page, rwc, true);
else
- return rmap_walk_file(page, rwc);
+ return rmap_walk_file(page, rwc, true);
}
#ifdef CONFIG_HUGETLB_PAGE
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-thp-fix-migration-of-pte-mapped-transparent-huge-pages.patch
thp-cleanup-split_huge_page.patch
thp-vmstats-count-deferred-split-events.patch
mm-tracing-refresh-__def_vmaflag_names.patch
mm-cleanup-pte_alloc-interfaces.patch
rmap-introduce-rmap_walk_locked.patch
rmap-extend-try_to_unmap-to-be-usable-by-split_huge_page.patch
mm-make-remove_migration_ptes-beyond-mm-migrationc.patch
thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-2.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-3.patch
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