Avi Kivity acc433b286 mutation_partition: make static_row optional to reduce memory footprint ...

The static row can be rare: many tables don't have them, and tables
that do will often have mutations without them (if the static row
is rarely updated, it may be present in the cache and in readers,
but absent in memtable mutations). However, it always consumes ~100
bytes of memory, even if it not present, due to row's overhead.

Change it to be optional by using lazy_row instead of row. Some call
sites treewide were adjusted to deal with the extra indirection.

perf_simple_query appears to improve by 2%, from 163krps to 165 krps,
though it's hard to be sure due to noisy measurements.

memory_footprint comparisons (before/after):

mutation footprint:		       mutation footprint:
 - in cache:	 1096		        - in cache:	992
 - in memtable:	 854		        - in memtable:	750
 - in sstable:	 351		        - in sstable:	351
 - frozen:	 540		        - frozen:	540
 - canonical:	 827		        - canonical:	827
 - query result: 342		        - query result: 342

 sizeof(cache_entry) = 112	        sizeof(cache_entry) = 112
 -- sizeof(decorated_key) = 36	        -- sizeof(decorated_key) = 36
 -- sizeof(cache_link_type) = 32        -- sizeof(cache_link_type) = 32
 -- sizeof(mutation_partition) = 200    -- sizeof(mutation_partition) = 96
 -- -- sizeof(_static_row) = 112        -- -- sizeof(_static_row) = 8
 -- -- sizeof(_rows) = 24	        -- -- sizeof(_rows) = 24
 -- -- sizeof(_row_tombstones) = 40     -- -- sizeof(_row_tombstones) = 40

 sizeof(rows_entry) = 232	        sizeof(rows_entry) = 232
 sizeof(lru_link_type) = 16	        sizeof(lru_link_type) = 16
 sizeof(deletable_row) = 168	        sizeof(deletable_row) = 168
 sizeof(row) = 112		        sizeof(row) = 112
 sizeof(atomic_cell_or_collection) = 8  sizeof(atomic_cell_or_collection) = 8

Tests: unit (dev)

2019-10-15 15:42:05 +03:00

18 KiB

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