[tarantool-patches] Re: [PATCH 7/9] vinyl: randomize range compaction to avoid IO load spikes

Konstantin Osipov kostja at tarantool.org
Wed Feb 6 16:43:41 MSK 2019

* Vladimir Davydov <vdavydov.dev at gmail.com> [19/02/06 14:53]:
> We know which run is last. Provided the workload is stable, i.e. have
> stopped growing its dataset, it will be roughly the same. Besides, the
> last level run size changes only on major compaction, which is
> infrequent.  After a major compaction, it's OK to use a different first
> level size - the point is in order not to break LSM algorithm, we have
> to maintain stable level sizing between major compactions.

The problem is that you can't use the last level as-is. You need a
divider, e.g. dumps_per_compaction, which is meaningless until the
first major compaction has happened.

Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

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