From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Hi all,
Kernel test robot reports -88.8% regression in stress-ng.ramfs.ops_per_sec
test case [1], which is caused by commit f95bdb700bc6 ("mm: vmscan: make
global slab shrink lockless"). The root cause is that SRCU has to be careful
to not frequently check for SRCU read-side critical section exits. Therefore,
even if no one is currently in the SRCU read-side critical section,
synchronize_srcu() cannot return quickly. That's why unregister_shrinker()
has become slower.
After discussion, we will try to use the refcount+RCU method [2] proposed
by Dave Chinner to continue to re-implement the lockless slab shrink. So
revert the shrinker_srcu related changes first.
[1]. https://lore.kernel.org/lkml/202305230837.db2c233f-yujie.liu@xxxxxxxxx/
[2]. https://lore.kernel.org/lkml/ZIJhou1d55d4H1s0@xxxxxxxxxxxxxxxxxxx/
And hi Andrew, the commit c3b5cb881de6 ("mm: vmscan: move
shrinker_debugfs_remove() before synchronize_srcu()") is still in the
mm-unstable branch, you can drop it directly.
This series is based on v6.4-rc5.
Thanks,
Qi
Qi Zheng (7):
Revert "mm: shrinkers: convert shrinker_rwsem to mutex"
Revert "mm: vmscan: remove shrinker_rwsem from
synchronize_shrinkers()"
Revert "mm: vmscan: hold write lock to reparent shrinker nr_deferred"
Revert "mm: shrinkers: make count and scan in shrinker debugfs
lockless"
Revert "mm: vmscan: add shrinker_srcu_generation"
Revert "mm: vmscan: make memcg slab shrink lockless"
Revert "mm: vmscan: make global slab shrink lockless"
drivers/md/dm-cache-metadata.c | 2 +-
drivers/md/dm-thin-metadata.c | 2 +-
fs/super.c | 2 +-
mm/shrinker_debug.c | 39 ++++++----
mm/vmscan.c | 125 +++++++++++++++------------------
5 files changed, 82 insertions(+), 88 deletions(-)
--
2.30.2
