mirror of
https://github.com/scylladb/scylladb.git
synced 2026-06-01 12:36:56 +00:00
20f4c9bf23
Currently eviction is performed until occupancy of the whole region drops below the 85% threshold. This may take a while if region had high occupancy and is large. We could improve the situation by only evicting until occupancy of the sparsest segment drops below the threshold, as is done by this change. I tested this using a c-s read workload in which the condition triggers in the cache region, with 1G per shard: lsa-timing - Reclamation cycle took 12.934 us. lsa-timing - Reclamation cycle took 47.771 us. lsa-timing - Reclamation cycle took 125.946 us. lsa-timing - Reclamation cycle took 144356 us. lsa-timing - Reclamation cycle took 655.765 us. lsa-timing - Reclamation cycle took 693.418 us. lsa-timing - Reclamation cycle took 509.869 us. lsa-timing - Reclamation cycle took 1139.15 us. The 144ms pause is when large eviction is necessary. Statistics for reclamation pauses for a read workload over larger-than-memory data set: Before: avg = 865.796362 stdev = 10253.498038 min = 93.891000 max = 264078.000000 sum = 574022.988000 samples = 663 After: avg = 513.685650 stdev = 275.270157 min = 212.286000 max = 1089.670000 sum = 340573.586000 samples = 663 Refs #1634. Message-Id: <1484730859-11969-1-git-send-email-tgrabiec@scylladb.com>