[PATCH 0/9 v3] locks: avoid thundering-herd wake-ups

From: NeilBrown
Date: Tue Oct 23 2018 - 18:45:39 EST

This took longer that I had wanted, due to various reasons - sorry.
And I'm now posting it in a merge window, which is not ideal. I don't
expect it to be included in this merge window and I won't be at all
impatient for review, but I didn't want to delay it further.

Testing found some problems, particularly the need to use
locks_copy_lock in NFS. And there was a small thinko in there that
effectively removed all the speed gains :-(

But this version:
- shows excellent scalability with lots of threads on lots of CPUs
contending on a single file
- avoids the problems that Bruce found
- seems to work.



NeilBrown (9):
fs/locks: rename some lists and pointers.
fs/locks: split out __locks_wake_up_blocks().
NFS: use locks_copy_lock() to copy locks.
fs/locks: allow a lock request to block other requests.
fs/locks: always delete_block after waiting.
fs/locks: change all *_conflict() functions to return bool.
fs/locks: create a tree of dependent requests.
locks: merge posix_unblock_lock() and locks_delete_block()
VFS: locks: remove unnecessary white space.

fs/cifs/file.c | 4 -
fs/lockd/svclock.c | 2
fs/locks.c | 231 ++++++++++++++++++++++-----------------
fs/nfs/nfs4proc.c | 6 +
fs/nfsd/nfs4state.c | 6 +
include/linux/fs.h | 11 +-
include/trace/events/filelock.h | 16 +--
7 files changed, 153 insertions(+), 123 deletions(-)