.Paged searches from a regular user now do not impact performance
Previously, when Directory Server was under the search load, paged searches from a regular user could impact the server performance because a lock conflicted with the thread that polls for network events. In addition, if a network issue occurred while sending the page search, the whole server was unresponsive until the `nsslapd-iotimeout` parameter expired. With this update, the lock was split into several parts to avoid the contention with the network events. As a result, no performance impact during paged searches from a regular user.
Description of problem:
When a server is under search load, a paged search from a regular user impacts the performance.
Same paged search requested by DM has much smaller impact.
Version-Release number of selected component (if applicable):
since 7.x
How reproducible:
systematic
Steps to Reproduce:
Create a db with 40000 users
Run search load using ldclt -D "uid=test,ou=people,dc=example,dc=com" -w test -e bindeach,esearch -b "ou=people,dc=example,dc=com" -f "uid=00001"
While the search load is running, run paged search in a loop that requests all ids:
while : ; do ldapsearch -D "uid=test,ou=people,dc=example,dc=com" -w test -b dc=example,dc=com 'uid=*' -E pr=100/noprompt; done
Actual results:
ldclt[1353]: Average rate: 2415.70/thr (2415.70/sec), total: 24157 -- only ldclt is running
ldclt[1353]: Average rate: 2342.50/thr (2342.50/sec), total: 23425
ldclt[1353]: Average rate: 1048.90/thr (1048.90/sec), total: 10489 -\
ldclt[1353]: Average rate: 413.10/thr ( 413.10/sec), total: 4131 | paged search from a regular user
ldclt[1353]: Average rate: 461.00/thr ( 461.00/sec), total: 4610 |
ldclt[1353]: Average rate: 1759.30/thr (1759.30/sec), total: 17593 -/
ldclt[1353]: Average rate: 2374.70/thr (2374.70/sec), total: 23747
ldclt[1353]: Average rate: 1952.70/thr (1952.70/sec), total: 19527 -\
ldclt[1353]: Average rate: 1783.00/thr (1783.00/sec), total: 17830 | paged search from DM
ldclt[1353]: Average rate: 1749.70/thr (1749.70/sec), total: 17497 -/
ldclt[1353]: Average rate: 2319.80/thr (2319.80/sec), total: 23198
ldclt[1353]: Average rate: 2378.80/thr (2378.80/sec), total: 23788
Expected results:
There shouldn't be a significant drop in performance.
Additional info:
@wisebaldone who reported the issue, also mentioned that 1.2.11.15-48 doesn't have the issue and 1.2.11.15-97 does have.
Comment 3RHEL Program Management
2022-12-21 07:27:55 UTC
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.
Comment 10RHEL Program Management
2023-06-21 07:28:16 UTC
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.
The issue is due to a very small lock contention impacting 0.3% of the server CPU time and 5% of the listening thread time but that was enough to decrease the performance by 60%.
Even worse we have seen case (after a network issue (tcp router restarted)) were the server was fully unresponsive until the nsslapd-ioblocktimeout expired.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (389-ds-base bug fix and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2023:6350
Description of problem: When a server is under search load, a paged search from a regular user impacts the performance. Same paged search requested by DM has much smaller impact. Version-Release number of selected component (if applicable): since 7.x How reproducible: systematic Steps to Reproduce: Create a db with 40000 users Run search load using ldclt -D "uid=test,ou=people,dc=example,dc=com" -w test -e bindeach,esearch -b "ou=people,dc=example,dc=com" -f "uid=00001" While the search load is running, run paged search in a loop that requests all ids: while : ; do ldapsearch -D "uid=test,ou=people,dc=example,dc=com" -w test -b dc=example,dc=com 'uid=*' -E pr=100/noprompt; done Actual results: ldclt[1353]: Average rate: 2415.70/thr (2415.70/sec), total: 24157 -- only ldclt is running ldclt[1353]: Average rate: 2342.50/thr (2342.50/sec), total: 23425 ldclt[1353]: Average rate: 1048.90/thr (1048.90/sec), total: 10489 -\ ldclt[1353]: Average rate: 413.10/thr ( 413.10/sec), total: 4131 | paged search from a regular user ldclt[1353]: Average rate: 461.00/thr ( 461.00/sec), total: 4610 | ldclt[1353]: Average rate: 1759.30/thr (1759.30/sec), total: 17593 -/ ldclt[1353]: Average rate: 2374.70/thr (2374.70/sec), total: 23747 ldclt[1353]: Average rate: 1952.70/thr (1952.70/sec), total: 19527 -\ ldclt[1353]: Average rate: 1783.00/thr (1783.00/sec), total: 17830 | paged search from DM ldclt[1353]: Average rate: 1749.70/thr (1749.70/sec), total: 17497 -/ ldclt[1353]: Average rate: 2319.80/thr (2319.80/sec), total: 23198 ldclt[1353]: Average rate: 2378.80/thr (2378.80/sec), total: 23788 Expected results: There shouldn't be a significant drop in performance. Additional info: @wisebaldone who reported the issue, also mentioned that 1.2.11.15-48 doesn't have the issue and 1.2.11.15-97 does have.