[dm-devel] [PATCHv2 0/6] dm-zoned: improve cache performance

[Hannes Reinecke]

Hi all,

here's an update to dm-zoned to separate out cache zones.
In the update to metadata version 2 the regular drive was split
in emulated zones, which were handled just like 'normal' random
write zones.
This causes a performance drop once these emulated zones have
been mapped, as typicall the random zones from the zoned drive
will perform noticeably slower than those from the regular drive.
(After all, that was kinda the idea of using a regular disk in
the first place ...)

So in this patchset I've introduced a separate 'cache' zone type,
allowing us to differentiate between emulated and real zones.
With that we can switch the allocation mode to use only cache
zones, and use random zones similar to sequential write zones.
That avoids the performance issue noted above.

I've also found that the sequential write zones perform noticeably
better on writes (which is all we're caching anyway), so I've
added another patch switching the allocation routine from preferring
sequential write zones for reclaim.

This patchset also contains some minor fixes like remving an unused
variable etc.

As usual, comments and reviews are welcome.

Changes to v1:
- Include reviews from Damien
- Introduce allocation flags
- Terminate reclaim on contention
- Rework original patch series

Hannes Reinecke (6):
  dm-zoned: return NULL if dmz_get_zone_for_reclaim() fails to find a
    zone
  dm-zoned: separate random and cache zones
  dm-zoned: reclaim random zones when idle
  dm-zoned: start reclaim with sequential zones
  dm-zoned: terminate reclaim on congestion
  dm-zoned: remove unused variable in dmz_do_reclaim()

 drivers/md/dm-zoned-metadata.c | 140 ++++++++++++++++++++++++++++++-----------
 drivers/md/dm-zoned-reclaim.c  | 109 ++++++++++++++++++++------------
 drivers/md/dm-zoned-target.c   |  19 ++++--
 drivers/md/dm-zoned.h          |  13 +++-
 4 files changed, 196 insertions(+), 85 deletions(-)

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2.16.4