Re: [PATCH v17 00/21] per memcg lru lock

Alex Shi
2020-07-27T05:40:55Z

A standard for new page isolation steps like the following:
1, get_page(); #pin the page avoid be free
2, TestClearPageLRU(); #serialize other isolation, also memcg change
3, spin_lock on lru_lock; #serialize lru list access
The step 2 could be optimzed/replaced in scenarios which page is unlikely
be accessed by others.

在 2020/7/25 下午8:59, Alex Shi 写道:
> The new version which bases on v5.8-rc6. It includes Hugh Dickins fix in
> mm/swap.c and mm/mlock.c fix which Alexander Duyck pointed out, then
> removes 'mm/mlock: reorder isolation sequence during munlock'
>
> Hi Johanness & Hugh & Alexander & Willy,
>
> Could you like to give a reviewed by since you address much of issue and
> give lots of suggestions! Many thanks!
>
> 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 new atomic func TestClearPageLRU.
> So now isolating a page need both actions: TestClearPageLRU and hold the
> lru_lock.
>
> The typical usage of 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, then 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 precondition
> 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 (19):
> 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: remove code path which never got into
> 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/thp: add tail pages into lru anyway in split_huge_page()
> mm/swap: serialize memcg changes in 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 | 48 +++--
> mm/memcontrol.c | 71 ++++++-
> mm/memory.c | 3 -
> mm/mlock.c | 43 +++--
> mm/mmzone.c | 1 +
> mm/page_alloc.c | 1 -
> mm/page_idle.c | 8 -
> mm/rmap.c | 4 +-
> mm/swap.c | 203 ++++++++-------------
> mm/swap_state.c | 2 -
> mm/vmscan.c | 174 ++++++++++--------
> mm/workingset.c | 2 -
> 25 files changed, 510 insertions(+), 344 deletions(-)
>