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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@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2016-03-17 14:20:01 -07:00 committed by Linus Torvalds
parent 99490f16f8
commit b97731992d
2 changed files with 33 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/rmap.h
View File

@ -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 */

41
mm/rmap.c
View File

@ -1715,14 +1715,21 @@ static struct anon_vma *rmap_walk_anon_lock(struct page *page,
* 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 *page, struct rmap_walk_control *rwc)
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 *page, struct rmap_walk_control *rwc)
* 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 *page, struct rmap_walk_control *rwc)
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 *page, struct rmap_walk_control *rwc)
}
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 rmap_walk_control *rwc)
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);
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, true);
}
#ifdef CONFIG_HUGETLB_PAGE