linux-toradex.git/mm/migrate.c, branch v5.13-rc3

mm: fix typos in comments

2021-05-07T07:26:35+00:00

Fix ~94 single-word typos in locking code comments, plus a few
very obvious grammar mistakes.

Link: https://lkml.kernel.org/r/20210322212624.GA1963421@gmail.com
Link: https://lore.kernel.org/r/20210322205203.GB1959563@gmail.com
Signed-off-by: Ingo Molnar 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: Randy Dunlap 
Cc: Bhaskar Chowdhury 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: cma: add trace events for CMA alloc perf testing

2021-05-05T18:27:24+00:00

Add cma and migrate trace events to enable CMA allocation performance to
be measured via ftrace.

[georgi.djakov@linaro.org: add the CMA instance name to the cma_alloc_start trace event]
  Link: https://lkml.kernel.org/r/20210326155414.25006-1-georgi.djakov@linaro.org

Link: https://lkml.kernel.org/r/20210324160740.15901-1-georgi.djakov@linaro.org
Signed-off-by: Liam Mark 
Signed-off-by: Georgi Djakov 
Acked-by: Minchan Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Revert "mm: migrate: skip shared exec THP for NUMA balancing"

2021-05-05T18:27:24+00:00

This reverts commit c77c5cbafe549eb330e8909861a3e16cbda2c848.

Since commit c77c5cbafe54 ("mm: migrate: skip shared exec THP for NUMA
balancing"), the NUMA balancing would skip shared exec transhuge page.
But this enhancement is not suitable for transhuge page.  Because it's
required that page_mapcount() must be 1 due to no migration pte dance is
done here.  On the other hand, the shared exec transhuge page will leave
the migrate_misplaced_page() with pte entry untouched and page locked.
Thus pagefault for NUMA will be triggered again and deadlock occurs when
we start waiting for the page lock held by ourselves.

Yang Shi said:

 "Thanks for catching this. By relooking the code I think the other
  important reason for removing this is
  migrate_misplaced_transhuge_page() actually can't see shared exec
  file THP at all since page_lock_anon_vma_read() is called before
  and if page is not anonymous page it will just restore the PMD
  without migrating anything.
  The pages for private mapped file vma may be anonymous pages due to
  COW but they can't be THP so it won't trigger THP numa fault at all. I
  think this is why no bug was reported. I overlooked this in the first
  place."

Link: https://lkml.kernel.org/r/20210325131524.48181-6-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: Yang Shi 
Cc: Alistair Popple 
Cc: David Hildenbrand 
Cc: Jerome Glisse 
Cc: Rafael Aquini 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate.c: use helper migrate_vma_collect_skip() in migrate_vma_collect_hole()

2021-05-05T18:27:24+00:00

It's more recommended to use helper function migrate_vma_collect_skip() to
skip the unexpected case and it also helps remove some duplicated codes.
Move migrate_vma_collect_skip() above migrate_vma_collect_hole() to avoid
compiler warning.

Link: https://lkml.kernel.org/r/20210325131524.48181-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Cc: Alistair Popple 
Cc: Jerome Glisse 
Cc: Rafael Aquini 
Cc: Yang Shi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate.c: fix potential indeterminate pte entry in migrate_vma_insert_page()

2021-05-05T18:27:24+00:00

If the zone device page does not belong to un-addressable device memory,
the variable entry will be uninitialized and lead to indeterminate pte
entry ultimately.  Fix this unexpected case and warn about it.

Link: https://lkml.kernel.org/r/20210325131524.48181-4-linmiaohe@huawei.com
Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Cc: Alistair Popple 
Cc: Jerome Glisse 
Cc: Rafael Aquini 
Cc: Yang Shi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate.c: remove unnecessary rc != MIGRATEPAGE_SUCCESS check in 'else' case

2021-05-05T18:27:24+00:00

It's guaranteed that in the 'else' case of the rc == MIGRATEPAGE_SUCCESS
check, rc does not equal to MIGRATEPAGE_SUCCESS.  Remove this unnecessary
check.

Link: https://lkml.kernel.org/r/20210325131524.48181-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Reviewed-by: Yang Shi 
Cc: Alistair Popple 
Cc: Jerome Glisse 
Cc: Rafael Aquini 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate.c: make putback_movable_page() static

2021-05-05T18:27:24+00:00

Patch series "Cleanup and fixup for mm/migrate.c", v3.

This series contains cleanups to remove unnecessary VM_BUG_ON_PAGE and rc
!= MIGRATEPAGE_SUCCESS check.  Also use helper function to remove some
duplicated codes.  What's more, this fixes potential deadlock in NUMA
balancing shared exec THP case and so on.  More details can be found in
the respective changelogs.

This patch (of 5):

The putback_movable_page() is just called by putback_movable_pages() and
we know the page is locked and both PageMovable() and PageIsolated() is
checked right before calling putback_movable_page().  So we make it static
and remove all the 3 VM_BUG_ON_PAGE().

Link: https://lkml.kernel.org/r/20210325131524.48181-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210325131524.48181-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: David Hildenbrand 
Reviewed-by: Yang Shi 
Cc: Jerome Glisse 
Cc: Rafael Aquini 
Cc: Alistair Popple 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: replace migrate_[prep|finish] with lru_cache_[disable|enable]

2021-05-05T18:27:24+00:00

Currently, migrate_[prep|finish] is merely a wrapper of
lru_cache_[disable|enable].  There is not much to gain from having
additional abstraction.

Use lru_cache_[disable|enable] instead of migrate_[prep|finish], which
would be more descriptive.

note: migrate_prep_local in compaction.c changed into lru_add_drain to
avoid CPU schedule cost with involving many other CPUs to keep old
behavior.

Link: https://lkml.kernel.org/r/20210319175127.886124-2-minchan@kernel.org
Signed-off-by: Minchan Kim 
Acked-by: Michal Hocko 
Reviewed-by: David Hildenbrand 
Cc: Chris Goldsworthy 
Cc: John Dias 
Cc: Matthew Wilcox 
Cc: Oliver Sang 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: disable LRU pagevec during the migration temporarily

2021-05-05T18:27:24+00:00

LRU pagevec holds refcount of pages until the pagevec are drained.  It
could prevent migration since the refcount of the page is greater than
the expection in migration logic.  To mitigate the issue, callers of
migrate_pages drains LRU pagevec via migrate_prep or lru_add_drain_all
before migrate_pages call.

However, it's not enough because pages coming into pagevec after the
draining call still could stay at the pagevec so it could keep
preventing page migration.  Since some callers of migrate_pages have
retrial logic with LRU draining, the page would migrate at next trail
but it is still fragile in that it doesn't close the fundamental race
between upcoming LRU pages into pagvec and migration so the migration
failure could cause contiguous memory allocation failure in the end.

To close the race, this patch disables lru caches(i.e, pagevec) during
ongoing migration until migrate is done.

Since it's really hard to reproduce, I measured how many times
migrate_pages retried with force mode(it is about a fallback to a sync
migration) with below debug code.

int migrate_pages(struct list_head *from, new_page_t get_new_page,
			..
			..

  if (rc && reason == MR_CONTIG_RANGE && pass > 2) {
         printk(KERN_ERR, "pfn 0x%lx reason %d", page_to_pfn(page), rc);
         dump_page(page, "fail to migrate");
  }

The test was repeating android apps launching with cma allocation in
background every five seconds.  Total cma allocation count was about 500
during the testing.  With this patch, the dump_page count was reduced
from 400 to 30.

The new interface is also useful for memory hotplug which currently
drains lru pcp caches after each migration failure.  This is rather
suboptimal as it has to disrupt others running during the operation.
With the new interface the operation happens only once.  This is also in
line with pcp allocator cache which are disabled for the offlining as
well.

Link: https://lkml.kernel.org/r/20210319175127.886124-1-minchan@kernel.org
Signed-off-by: Minchan Kim 
Reviewed-by: Chris Goldsworthy 
Acked-by: Michal Hocko 
Cc: John Dias 
Cc: Suren Baghdasaryan 
Cc: Matthew Wilcox 
Cc: David Hildenbrand 
Cc: Vlastimil Babka 
Cc: Oliver Sang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/page_alloc: combine __alloc_pages and __alloc_pages_nodemask

2021-04-30T18:20:42+00:00

There are only two callers of __alloc_pages() so prune the thicket of
alloc_page variants by combining the two functions together.  Current
callers of __alloc_pages() simply add an extra 'NULL' parameter and
current callers of __alloc_pages_nodemask() call __alloc_pages() instead.

Link: https://lkml.kernel.org/r/20210225150642.2582252-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Acked-by: Vlastimil Babka 
Acked-by: Michal Hocko 
Cc: Mike Rapoport 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds