These patches contain some minor fixes for performance regression reported
by perf_fast_forward after partial cache was merged. The solution is still
far from perfect, there is one case that still has 30% degradation, but
there is some improvement so there is no reason to hold these changes back.
Refs #2582.
Some numbers:
before - before cache changes were merged
(555621b537)
cache - at the commit that introduced the partial cache
(9b21a9bfb6)
after - recent master + this series
(based on e988121dbb)
Differences are shown relative to "before".
Testing effectiveness of caching of large partition, single-key slicing reads:
Large partitions, range [0, 500000], populating cache
before cache after
1636840 1013688 1234606
-38% -25%
Large partitions, range [0, 500000], reading from cache
before cache after
2012615 3076812 3035423
+53% +51%
Testing scanning small partitions with skips.
reading small partitions (skip 0)
before cache after
227060 165261 200639
-27% -11%
skipping small partitions (skip 1)
before cache after
29813 27312 38210
-8% +28%
Testing slicing small partitions:
slicing small partitions (offset 0, read 4096)
before cache after
195282 149695 180497
-23% -8%
* https://github.com/pdziepak/scylla.git perf_fast_forward-regression/v3:
sstables: make sure that fill_buffer() actually fills buffer
mutation_merger: improve handling of non-deferring fill_buffer()s
partition_snapshot_row_cursor: avoid apply() in single-version cases
sstables: introduce decorated_key_view
ring_position_comparator: accept sstables::decorated_key_view
sstable: keep a pre-computed token in summary_entry
sstables: cache token in index entries
index_reader: advance_and_check_if_present() use index_comparator
ring_position_comparator: drop unused overloads
cache_streamed_mutation: avoid moving clustering_row
streamed_mutation: introduce consume_mutation_fragments_until()
cache_streamed_mutation: use consumer based read_context reader
rows_entry: make position() inlineable
mutation_fragment: make destructor always_inline
keys: introduce compound_wrapper::from_exploded_view()
sstables: avoid copying key components
compound_compat: explode: reserve some elements in a vector
cache: short-circut static row logic if there are no static columns
cache: use equality comparators instead of tri_compare
sstables: avoid indirect calls to abstract_type::is_multi_cell()
(cherry picked from commit e9fc0b0491)
5857a4756d