Compaction time increased by 40-50 mins from 7.5.0-4421 to 7.6.0-1295

We are seeing some significant compaction time increases from 7.5.0-4421 to 7.6.0-1295 in our two below compaction tests:

• http://showfast.sc.couchbase.com/#/timeline/Linux/kv/compa ct/all#kv_compact_1000M_fe_1000s_1000c_athena
  
• http://showfast.sc.couchbase.com /#/ti meline/Linux/kv/compact/all#kv_compact_1000M_fe_1s_1c_athena
  

Test	CB build	Compaction time (mins)	Jenkins link	Cbmonitor link	Cbcollects
Full compaction time (min), 4 nodes, 1B x 1KB, 15K ops/sec (90/10 R/W), 5% cache miss rate, s=1000 c=1000	7.5.0-4421	271.7	link	link	compact_1000s_1000c_750_4421_cen-sc31.perf.couchbase.com.zip compact_1000s_1000c_750_4421_cen-sc34.perf.couchbase.com.zip compact_1000s_1000c_750_4421_cen-sc33.perf.couchbase.com.zip compact_1000s_1000c_750_4421_cen-sc32.perf.couchbase.com.zip
Full compaction time (min), 4 nodes, 1B x 1KB, 15K ops/sec (90/10 R/W), 5% cache miss rate, s=1000 c=1000	7.6.0-1295	310.2	link	link	compact_1000s_1000c_760_1295_cen-sc31.perf.couchbase.com.zip compact_1000s_1000c_760_1295_cen-sc34.perf.couchbase.com.zip compact_1000s_1000c_760_1295_cen-sc33.perf.couchbase.com.zip compact_1000s_1000c_760_1295_cen-sc32.perf.couchbase.com.zip
Full compaction time (min), 4 nodes, 1B x 1KB, 15K ops/sec (90/10 R/W), 5% cache miss rate, s=1 c=1	7.5.0-4421	163.8	link	link	compact_1s_1c_750_4421_cen-sc31.perf.couchbase.com.zip compact_1s_1c_750_4421_cen-sc34.perf.couchbase.com.zip compact_1s_1c_750_4421_cen-sc33.perf.couchbase.com.zip compact_1s_1c_750_4421_cen-sc32.perf.couchbase.com.zip
Full compaction time (min), 4 nodes, 1B x 1KB, 15K ops/sec (90/10 R/W), 5% cache miss rate, s=1 c=1	7.6.0-1295	215.8	link	link	compact_1s_1c_760_1295_cen-sc34.perf.couchbase.com.zip compact_1s_1c_760_1295_cen-sc33.perf.couchbase.com.zip compact_1s_1c_760_1295_cen-sc32.perf.couchbase.com.zip compact_1s_1c_760_1295_cen-sc31.perf.couchbase.com.zip

Cbmonitor comparison reports:

• Test 1 (1000s 1000c): http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=athena_750-4421_compact_58c7&snapshot=athena_760-1295_compact_f0de
• Test 2 (1s 1c): http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=athena_750-4421_compact_0345&snapshot=athena_760-1295_compact_8c7b