[PATCH v14 00/20] per memcg lru lock

Alex Shi
2020-07-03T05:09:59Z

This is a new version which bases on v5.8-rc3.

Current lru_lock is one for each of node, pgdat->lru_lock, that guard for
lru lists, but now we had moved the lru lists into memcg for long time. Still
using per node lru_lock is clearly unscalable, pages on each of memcgs have
to compete each others for a whole lru_lock. This patchset try to use per
lruvec/memcg lru_lock to repleace per node lru lock to guard lru lists, make
it scalable for memcgs and get performance gain.

Currently lru_lock still guards both lru list and page's lru bit, that's ok.
but if we want to use specific lruvec lock on the page, we need to pin down
the page's lruvec/memcg during locking. Just taking lruvec lock first may be
undermined by the page's memcg charge/migration. To fix this problem, we could
take out the page's lru bit clear and use it as pin down action to block the
memcg changes. That's the reason for atomic func TestClearPageLRU.
So now isolating a page need both actions: TestClearPageLRU and hold the
lru_lock.

The typic using for this is isolate_migratepages_block() in compaction.c
we have to take lru bit before lru lock, that serialized the page isolation
in memcg page charge/migration which will change page's lruvec and new
lru_lock in it.

The above solution suggested by Johannes Weiner, and based on his new memcg
charge path, we have this patchset. (Hugh Dickins tested and contributed much
code from compaction fix to general code polish, thanks a lot!).

The patchset includes 3 parts:
1, some code cleanup and minimum optimization as a preparation.
2, use TestCleanPageLRU as page isolation's condition
3, replace per node lru_lock with per memcg per node lru_lock

Following Daniel Jordan's suggestion, I have run 208 'dd' with on 104
containers on a 2s * 26cores * HT box with a modefied case:
https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git/tree/case-lru-file-readtwice
With this patchset, the readtwice performance increased about 80%
in concurrent containers.

Thanks Hugh Dickins and Konstantin Khlebnikov, they both brought this
idea 8 years ago, and others who give comments as well: Daniel Jordan,
Mel Gorman, Shakeel Butt, Matthew Wilcox etc.

Thanks for Testing support from Intel 0day and Rong Chen, Fengguang Wu,
and Yun Wang. Hugh Dickins also shared his kbuild-swap case. Thanks!

Alex Shi (18):
mm/vmscan: remove unnecessary lruvec adding
mm/page_idle: no unlikely double check for idle page counting
mm/compaction: correct the comments of compact_defer_shift
mm/compaction: rename compact_deferred as compact_should_defer
mm/thp: move lru_add_page_tail func to huge_memory.c
mm/thp: clean up lru_add_page_tail
mm/thp: narrow lru locking
mm/memcg: add debug checking in lock_page_memcg
mm/swap: fold vm event PGROTATED into pagevec_move_tail_fn
mm/lru: move lru_lock holding in func lru_note_cost_page
mm/lru: move lock into lru_note_cost
mm/lru: introduce TestClearPageLRU
mm/compaction: do page isolation first in compaction
mm/mlock: reorder isolation sequence during munlock
mm/swap: serialize memcg changes during pagevec_lru_move_fn
mm/lru: replace pgdat lru_lock with lruvec lock
mm/lru: introduce the relock_page_lruvec function
mm/pgdat: remove pgdat lru_lock

Hugh Dickins (2):
mm/vmscan: use relock for move_pages_to_lru
mm/lru: revise the comments of lru_lock

Documentation/admin-guide/cgroup-v1/memcg_test.rst | 15 +-
Documentation/admin-guide/cgroup-v1/memory.rst | 21 ++-
Documentation/trace/events-kmem.rst | 2 +-
Documentation/vm/unevictable-lru.rst | 22 +--
include/linux/compaction.h | 4 +-
include/linux/memcontrol.h | 98 ++++++++++++
include/linux/mm_types.h | 2 +-
include/linux/mmzone.h | 6 +-
include/linux/page-flags.h | 1 +
include/linux/swap.h | 4 +-
include/trace/events/compaction.h | 2 +-
mm/compaction.c | 113 +++++++++----
mm/filemap.c | 4 +-
mm/huge_memory.c | 53 ++++--
mm/memcontrol.c | 71 ++++++++-
mm/memory.c | 3 -
mm/mlock.c | 93 +++++------
mm/mmzone.c | 1 +
mm/page_alloc.c | 1 -
mm/page_idle.c | 8 -
mm/rmap.c | 4 +-
mm/swap.c | 177 +++++++--------------
mm/swap_state.c | 2 -
mm/vmscan.c | 174 ++++++++++----------
mm/workingset.c | 2 -
25 files changed, 518 insertions(+), 365 deletions(-)

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1.8.3.1