db/config.cc: increment components_memory_reclaim_threshold config de…

…fault

Incremented the components_memory_reclaim_threshold config's default
value to 0.2 as the previous value was too strict and caused unnecessary
eviction in otherwise healthy clusters.

Fixes #18607

Signed-off-by: Lakshmi Narayanan Sreethar <lakshmi.sreethar@scylladb.com>
(cherry picked from commit 3d7d1fa)

Closes #19011

db/config.cc

@@ -819,7 +819,7 @@ db::config::config(std::shared_ptr<db::extensions> exts)
     , unspooled_dirty_soft_limit(this, "unspooled_dirty_soft_limit", value_status::Used, 0.6, "Soft limit of unspooled dirty memory expressed as a portion of the hard limit")
     , sstable_summary_ratio(this, "sstable_summary_ratio", value_status::Used, 0.0005, "Enforces that 1 byte of summary is written for every N (2000 by default) "
         "bytes written to data file. Value must be between 0 and 1.")
-    , components_memory_reclaim_threshold(this, "components_memory_reclaim_threshold", liveness::LiveUpdate, value_status::Used, .1, "Ratio of available memory for all in-memory components of SSTables in a shard beyond which the memory will be reclaimed from components until it falls back under the threshold. Currently, this limit is only enforced for bloom filters.")
+    , components_memory_reclaim_threshold(this, "components_memory_reclaim_threshold", liveness::LiveUpdate, value_status::Used, .2, "Ratio of available memory for all in-memory components of SSTables in a shard beyond which the memory will be reclaimed from components until it falls back under the threshold. Currently, this limit is only enforced for bloom filters.")
     , large_memory_allocation_warning_threshold(this, "large_memory_allocation_warning_threshold", value_status::Used, size_t(1) << 20, "Warn about memory allocations above this size; set to zero to disable")
     , enable_deprecated_partitioners(this, "enable_deprecated_partitioners", value_status::Used, false, "Enable the byteordered and random partitioners. These partitioners are deprecated and will be removed in a future version.")
     , enable_keyspace_column_family_metrics(this, "enable_keyspace_column_family_metrics", value_status::Used, false, "Enable per keyspace and per column family metrics reporting")

test/boost/sstable_datafile_test.cc

@@ -3573,7 +3573,7 @@ SEASTAR_TEST_CASE(test_sstable_manager_auto_reclaim_and_reload_of_bloom_filter)
     }, {
         // limit available memory to the sstables_manager to test reclaiming.
         // this will set the reclaim threshold to 100 bytes.
-        .available_memory = 1000
+        .available_memory = 500
     });
 }
 
@@ -3654,6 +3654,6 @@ SEASTAR_TEST_CASE(test_bloom_filter_reclaim_during_reload) {
     }, {
         // limit available memory to the sstables_manager to test reclaiming.
         // this will set the reclaim threshold to 100 bytes.
-        .available_memory = 1000
+        .available_memory = 500
     });
 }