Am 08.04.25 um 22:56 schrieb Norbert:
Hi,
Am 08.04.25 um 12:32 schrieb Ondřej Kuzník:
just a thought:
It looks like you also have a "sub"string index on that attribute, all indexes for a given attribute exist in the same namespace and a substring index generates a *lot* of items. So you'll get false positives competing for slapd's attention - have you enabled 64bit hashes already ("index_hash64 on")?
Should help with the contention if you haven't yet.
I did two further tests:
- olcIndexHash64: TRUE
- olcIndexHash64: TRUE and only keeping eq for almost_uniqe_attr
in both cases config and data was wiped and re-created with slapadd I confirmed that keysize is now 64bit in the index.
mdb_stat for the index with eq,sub and 32bit index keys from a running server Status of almost_uniqe_attr Tree depth: 3 Branch pages: 256 Leaf pages: 47269 Overflow pages: 0 Entries: 47486472
mdb_stat for index with eq only and 64bit index keys after fresh import Status of almost_uniqe_attr Tree depth: 4 Branch pages: 261 Leaf pages: 41908 Overflow pages: 0 Entries: 3931262
Unfortunately there was no change in runtime. The 1200 queries still take around 11s, might be even a tiny bit slower with 12s.
When running those 1200 filters and recording activity with perf in parallel I get at the top
# Samples: 45K of event 'cpu-clock:pppH' # Event count (approx.): 11330500000 # # Children Self Command Shared Object Symbol # ........ ........ ....... ....................... ............................................. # 41.12% 40.82% slapd back_mdb-2.5.so.0.1.14 [.] mdb_idl_next | ---mdb_idl_next
31.71% 31.55% slapd back_mdb-2.5.so.0.1.14 [.] mdb_idl_intersection | ---mdb_idl_intersection
24.25% 24.11% slapd back_mdb-2.5.so.0.1.14 [.] mdb_idl_next@plt | ---mdb_idl_next@plt
1.13% 0.00% slapd [kernel.kallsyms] [k] entry_SYSCALL_64_after_hwframe | ---entry_SYSCALL_64_after_hwframe |
And when removing the second entry I get for the same 1200 filters following recorded
# Samples: 420 of event 'cpu-clock:pppH' # Event count (approx.): 105000000 # # Children Self Command Shared Object Symbol # ........ ........ ....... ....................... ....................................... # 41.90% 0.00% slapd [kernel.kallsyms] [k] entry_SYSCALL_64_after_hwframe | ---entry_SYSCALL_64_after_hwframe | |--41.19%--do_syscall_64 | | | |--22.62%--ksys_write
Thanks, Norbert