replica: Use flat_hash_map for tablet storage
The reason that we want to switch to flat_hash_map is that only a small
subset of tablets will be allocated on any given shard, therefore it's
wasteful to use a sparse array, and iterations are slow.
Also, the map gives greater development flexibility as one doesn't have
to worry about empty entries.
perf result:
-- reads
scylla_with_chunked_vector-read-no-tablets.txt
median 73223.28 tps ( 62.3 allocs/op, 13.3 tasks/op, 41932 insns/op, 0 errors)
median 74952.87 tps ( 62.3 allocs/op, 13.3 tasks/op, 41969 insns/op, 0 errors)
median 73016.37 tps ( 62.3 allocs/op, 13.3 tasks/op, 41934 insns/op, 0 errors)
median 74078.14 tps ( 62.3 allocs/op, 13.3 tasks/op, 41938 insns/op, 0 errors)
median 75323.07 tps ( 62.3 allocs/op, 13.3 tasks/op, 41944 insns/op, 0 errors)
scylla_with_hash_map-read-no-tablets.txt
median 74963.30 tps ( 62.3 allocs/op, 13.3 tasks/op, 41926 insns/op, 0 errors)
median 74032.09 tps ( 62.3 allocs/op, 13.3 tasks/op, 41918 insns/op, 0 errors)
median 74850.09 tps ( 62.3 allocs/op, 13.3 tasks/op, 41937 insns/op, 0 errors)
median 74239.37 tps ( 62.3 allocs/op, 13.3 tasks/op, 41921 insns/op, 0 errors)
median 74798.14 tps ( 62.3 allocs/op, 13.3 tasks/op, 41925 insns/op, 0 errors)
scylla_with_chunked_vector-read-tablets-1.txt
median 74234.27 tps ( 62.1 allocs/op, 13.3 tasks/op, 41903 insns/op, 0 errors)
median 75775.98 tps ( 62.1 allocs/op, 13.3 tasks/op, 41910 insns/op, 0 errors)
median 76481.56 tps ( 62.1 allocs/op, 13.2 tasks/op, 41874 insns/op, 0 errors)
median 74056.67 tps ( 62.1 allocs/op, 13.3 tasks/op, 41894 insns/op, 0 errors)
median 75287.68 tps ( 62.1 allocs/op, 13.3 tasks/op, 41894 insns/op, 0 errors)
scylla_with_hash_map-read-tablets-1.txt
median 75613.63 tps ( 62.1 allocs/op, 13.2 tasks/op, 41990 insns/op, 0 errors)
median 74819.51 tps ( 62.1 allocs/op, 13.2 tasks/op, 41973 insns/op, 0 errors)
median 75648.41 tps ( 62.1 allocs/op, 13.3 tasks/op, 42025 insns/op, 0 errors)
median 74170.89 tps ( 62.1 allocs/op, 13.2 tasks/op, 42002 insns/op, 0 errors)
median 75447.72 tps ( 62.1 allocs/op, 13.3 tasks/op, 41952 insns/op, 0 errors)
scylla_with_chunked_vector-read-tablets-128.txt
median 73788.57 tps ( 62.1 allocs/op, 13.2 tasks/op, 41956 insns/op, 0 errors)
median 76563.63 tps ( 62.1 allocs/op, 13.3 tasks/op, 42006 insns/op, 0 errors)
median 75536.12 tps ( 62.1 allocs/op, 13.2 tasks/op, 42005 insns/op, 0 errors)
median 74679.17 tps ( 62.1 allocs/op, 13.3 tasks/op, 41958 insns/op, 0 errors)
median 75380.95 tps ( 62.1 allocs/op, 13.2 tasks/op, 41946 insns/op, 0 errors)
scylla_with_hash_map-read-tablets-128.txt
median 75459.99 tps ( 62.1 allocs/op, 13.3 tasks/op, 42055 insns/op, 0 errors)
median 74280.11 tps ( 62.1 allocs/op, 13.3 tasks/op, 42085 insns/op, 0 errors)
median 74502.61 tps ( 62.1 allocs/op, 13.3 tasks/op, 42063 insns/op, 0 errors)
median 74692.27 tps ( 62.1 allocs/op, 13.3 tasks/op, 41994 insns/op, 0 errors)
median 75402.64 tps ( 62.1 allocs/op, 13.3 tasks/op, 42015 insns/op, 0 errors)
-- writes
scylla_with_chunked_vector-write-no-tablets.txt
median 68635.17 tps ( 58.4 allocs/op, 13.3 tasks/op, 52709 insns/op, 0 errors)
median 68716.36 tps ( 58.4 allocs/op, 13.3 tasks/op, 52691 insns/op, 0 errors)
median 68512.76 tps ( 58.4 allocs/op, 13.3 tasks/op, 52721 insns/op, 0 errors)
median 68606.14 tps ( 58.4 allocs/op, 13.3 tasks/op, 52696 insns/op, 0 errors)
median 68619.25 tps ( 58.4 allocs/op, 13.3 tasks/op, 52697 insns/op, 0 errors)
scylla_with_hash_map-write-no-tablets.txt
median 67678.10 tps ( 58.4 allocs/op, 13.3 tasks/op, 52723 insns/op, 0 errors)
median 67966.06 tps ( 58.4 allocs/op, 13.3 tasks/op, 52736 insns/op, 0 errors)
median 67881.47 tps ( 58.4 allocs/op, 13.3 tasks/op, 52743 insns/op, 0 errors)
median 67856.81 tps ( 58.4 allocs/op, 13.3 tasks/op, 52730 insns/op, 0 errors)
median 67812.58 tps ( 58.4 allocs/op, 13.3 tasks/op, 52740 insns/op, 0 errors)
scylla_with_chunked_vector-write-tablets-1.txt
median 67741.83 tps ( 58.4 allocs/op, 13.3 tasks/op, 53425 insns/op, 0 errors)
median 68014.20 tps ( 58.4 allocs/op, 13.3 tasks/op, 53455 insns/op, 0 errors)
median 68228.48 tps ( 58.4 allocs/op, 13.3 tasks/op, 53447 insns/op, 0 errors)
median 67950.96 tps ( 58.4 allocs/op, 13.3 tasks/op, 53443 insns/op, 0 errors)
median 67832.69 tps ( 58.4 allocs/op, 13.3 tasks/op, 53462 insns/op, 0 errors)
scylla_with_hash_map-write-tablets-1.txt
median 66873.70 tps ( 58.4 allocs/op, 13.3 tasks/op, 53548 insns/op, 0 errors)
median 67568.23 tps ( 58.4 allocs/op, 13.3 tasks/op, 53547 insns/op, 0 errors)
median 67653.70 tps ( 58.4 allocs/op, 13.3 tasks/op, 53525 insns/op, 0 errors)
median 67389.21 tps ( 58.4 allocs/op, 13.3 tasks/op, 53536 insns/op, 0 errors)
median 67437.91 tps ( 58.4 allocs/op, 13.3 tasks/op, 53537 insns/op, 0 errors)
scylla_with_chunked_vector-write-tablets-128.txt
median 67115.41 tps ( 58.3 allocs/op, 13.3 tasks/op, 53341 insns/op, 0 errors)
median 66836.07 tps ( 58.3 allocs/op, 13.3 tasks/op, 53342 insns/op, 0 errors)
median 67214.07 tps ( 58.3 allocs/op, 13.3 tasks/op, 53303 insns/op, 0 errors)
median 67198.25 tps ( 58.3 allocs/op, 13.3 tasks/op, 53347 insns/op, 0 errors)
median 67368.78 tps ( 58.3 allocs/op, 13.3 tasks/op, 53374 insns/op, 0 errors)
scylla_with_hash_map-write-tablets-128.txt
median 66273.50 tps ( 58.3 allocs/op, 13.3 tasks/op, 53400 insns/op, 0 errors)
median 66564.89 tps ( 58.3 allocs/op, 13.3 tasks/op, 53432 insns/op, 0 errors)
median 66568.52 tps ( 58.3 allocs/op, 13.3 tasks/op, 53408 insns/op, 0 errors)
median 66368.00 tps ( 58.3 allocs/op, 13.3 tasks/op, 53441 insns/op, 0 errors)
median 66293.55 tps ( 58.3 allocs/op, 13.3 tasks/op, 53408 insns/op, 0 errors)
Fixes #18010.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closes scylladb/scylladb#18093
9f93dd9fa3