[Devel] [RFC PATCH vz9 v6 00/62] 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.

v6 changes:
 - locking fixes
 - use READ_ONCE/WRITE_ONCE
 - properly handle DIO errors (ENOTBLK)
 - added support for data pios with REQ_FUA
 - convert more lists to lockless variants
 - resize/grow is good

v5 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 bugs:
  - delayed metadata writeback is not working and is missing error handling
     - patch to disable it until fixed
  - fast path is not working - causes rcu lockups - patch to disable it

Further improvements:
  - make metadata writeback work in parallel
  - fsync to end pios in parallel, ready but depends on parallel metadata

Alexander Atanasov (49):
  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 unnecessary 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: 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
  dm-ploop: use lockless lists for chained cow updates list
  dm-ploop: use lockless lists for data ready pios
  dm-ploop: give runner threads better name
  dm-ploop: resize operation - add holes bitmap locking
  dm-ploop: remove unnecessary operations
  dm-ploop: use filp per thread
  dm-ploop: catch if we try to advance pio past bio end
  dm-ploop: support REQ_FUA for data pios
  dm-ploop: proplerly access nr_bat_entries
  dm-ploop: fix locking and improve error handling when submitting pios
  dm-ploop: fix how ENOTBLK is handled
  dm-ploop: sync when suspended or stopping
  dm-ploop: rework bat completion logic
  dm-ploop: rework logic in pio processing

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    |   73 +-
 drivers/md/dm-ploop-cmd.c    |  169 +++--
 drivers/md/dm-ploop-map.c    | 1333 +++++++++++++++++++++++-----------
 drivers/md/dm-ploop-target.c |  137 +++-
 drivers/md/dm-ploop.h        |  106 ++-
 5 files changed, 1241 insertions(+), 577 deletions(-)

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2.43.0