[Devel] [RFC PATCH vz9 v5 00/49] ploop optimistations and scalling

[Alexander Atanasov]

Ploop processes requsts in a different threads in parallel
where possible which results in significant improvement in
performance and makes further optimistations possible.

Along with changes in v4:
 - BAT writeback delay
 - Lists/Locking moving to lockless lists to reduce locking
 - Requests are prepared in the caller to reduce load of worker thread
 - REQ_FUA and REQ_PREFLUSH support
 - Convert bit fields to use atomic bitops - reduce locking
 - remove fsync worker to guarantee order of execution
 - Map all md pages at creation time - they are only freed on device destroy

Known bug:
  - resize/grow is not working yet
  - delayed metadata writeback is not working - patch to disable it for testing
  - fast path is not working too - rcu lockups - patch to disable it for testing

Further improvements:
  - make metadata writeback work in parallel
  - fsync to end pios in parallel


Alexander Atanasov (36):
  dm-ploop: md_pages map all pages at creation time
  dm-ploop: Use READ_ONCE/WRITE_ONCE to access md page data
  dm-ploop: fsync after all pios are sent
  dm-ploop: move md status to use proper bitops
  dm-ploop: remove unneccessary lock
  dm-ploop: reduce the time lock is hold, taking it only to protect data
  dm-ploop: convert wait_list and wb_batch_llist to use lockless lists
  dm-ploop: convert enospc handling to use lockless lists
  dm-ploop: convert suspended_pios list to use lockless list
  dm-ploop: convert the rest of the lists to use llist variant
  dm-ploop: combine processing of pios thru prepare list and remove
    fsync worker
  dm-ploop: WIP move from wq to kthread
  dm-ploop: complete conversion of enospc and suspended pios to lockless
  dm-ploop: move preparations of pios into the caller from worker
  dm-ploop: fast path execution for reads
  dm-ploop: do not use a wrapper for set_bit to make a page writeback
  dm-ploop: BAT use only one list for writeback
  dm-ploop: make md writeback timeout to be per page
  dm-ploop: add interface to disable bat writeback delay
  dm-ploop: convert wb_batch_list to lockless variant
  dm-ploop: convert high_prio to status
  dm-ploop: split cow processing into two functions
  dm-ploop: debug patch , keep on top of stack
  dm-ploop: use jiffies when calculating writeback time
  dm-ploop: convert md page rw lock to spin lock
  dm-ploop: convert bat_rwlock to bat_lock spinlock
  dm-ploop: prepare bat updates under bat_lock
  dm-ploop: make ploop_bat_write_complete ready for parallel pio
    completion
  dm-ploop: fix access to batpages to use WRITE_ONCE
  dm-ploop: properly end pios attached to piwb pios
  dm-ploop: make ploop_submit_metadata_writeback return number of
    requests sent
  dm-ploop: introduce pio runner threads
  dm-ploop: add pio list ids to be used when passing pios to runners
  dm-ploop: process pios via runners
  dm-ploop: disable metadata writeback delay
  dm-ploop: disable fast path

Andrey Zhadchenko (13):
  dm-ploop: do not flush after metadata writes
  dm-ploop: set IOCB_DSYNC on all FUA requests
  dm-ploop: remove extra ploop_cluster_is_in_top_delta()
  dm-ploop: simplify llseek
  dm-ploop: reduce BAT accesses on discard completion
  dm-ploop: introduce per-md page locking
  dm-ploop: speed up ploop_prepare_bat_update()
  dm-ploop: make new allocations immediately visible in BAT
  dm-ploop: drop ploop_cluster_is_in_top_delta()
  dm-ploop: do not wait for BAT update for non-FUA requests
  dm-ploop: add delay for metadata writeback
  dm-ploop: submit all postponed metadata on REQ_OP_FLUSH
  dm-ploop: handle REQ_PREFLUSH

 drivers/md/dm-ploop-bat.c    |   58 +-
 drivers/md/dm-ploop-cmd.c    |  137 ++--
 drivers/md/dm-ploop-map.c    | 1153 ++++++++++++++++++++++++----------
 drivers/md/dm-ploop-target.c |  142 ++++-
 drivers/md/dm-ploop.h        |   96 ++-
 5 files changed, 1099 insertions(+), 487 deletions(-)

-- 
2.43.0