[0/4] dm vdo: reduce reference count load time

Message

Matthew Sakai Feb. 1, 2025, 2:18 a.m. UTC

A vdo device loads all reference count values at startup, reading
entire spans of up to a few MB at a time. Use a small number of large
vios instead of a big flurry of 4kB vios to read this data more
efficiently.

On our test systems (KVM virtual machines with 6 Intel Icelake cores
and 16 GB RAM, simulating ~34 TB of physical storage through some
device-mapper hackery), using the larger vios cuts the vdo startup
time by 15-30%. Installations with smaller or very fast storage may
see less benefit.

Ken Raeburn (4):
  dm vdo vio-pool: add a pool pointer to pooled_vio
  dm vdo vio-pool: support pools with multiple data blocks per vio
  dm vdo vio-pool: allow variable-sized metadata vios
  dm vdo slab-depot: read refcount blocks in large chunks at load time

 drivers/md/dm-vdo/block-map.c    | 11 ++---
 drivers/md/dm-vdo/io-submitter.c |  6 ++-
 drivers/md/dm-vdo/io-submitter.h | 18 +++++--
 drivers/md/dm-vdo/slab-depot.c   | 80 ++++++++++++++++++++++----------
 drivers/md/dm-vdo/slab-depot.h   | 13 +++++-
 drivers/md/dm-vdo/types.h        |  3 ++
 drivers/md/dm-vdo/vio.c          | 54 ++++++++++++---------
 drivers/md/dm-vdo/vio.h          | 13 ++++--
 8 files changed, 136 insertions(+), 62 deletions(-)