Thanks Lukas for the review! I've modified and re-did the patch and uploaded. Please take a look. Thanks.
** Attachment added: "questing-debdiff-sep23.txt" https://bugs.launchpad.net/ubuntu/+source/libnss-db/+bug/2121543/+attachment/5911033/+files/questing-debdiff-sep23.txt -- You received this bug notification because you are a member of Debcrafters packages, which is subscribed to libnss-db in Ubuntu. https://bugs.launchpad.net/bugs/2121543 Title: [SRU] Poor performance of libnss-db on large db files Status in libnss-db package in Ubuntu: In Progress Status in libnss-db source package in Noble: New Status in libnss-db source package in Plucky: New Status in libnss-db source package in Questing: In Progress Bug description: libdnss-db opens and closes the DB file each time. This is normally not an issue as the DB files are small. However, in a user environment, this takes considerably longer because the DB files have entries to the tune of 20k which severely impacts the performance of lookups. ---- [ Impact ] The libnss-db library, which processes Berkeley DB files, closes and re-opens the DB file for each entry in the file that it currently scans. This results in very poor performance and noticiable botteneck on the application side. In a user environment that has 20k entries in the DB, this results in about 40 times worse performance (compared to keeping the file open). [ Test Plan ] The test plan sets up some DB files and queries them to see if the open(2) and close(2) calls are repeatedly called. 1. update /etc/default/libnss-db DBS = passwd group shadow VAR_DB = /var/lib/misc ETC = ${VAR_DB}/etc AWK = awk MAKEDB = makedb --quiet 2. update /etc/nsswitch.conf passwd: files systemd db group: files systemd db shadow: files systemd db 3. create required files mkdir -p /var/lib/misc/etc touch /var/lib/misc/etc/{passwd,group,shadow} cp /etc/login.defs /var/lib/misc/etc 4. update /var/lib/misc/etc/login.defs so that UIDs are less likely to conflict UID_MIN 5000 5. create test users in berkelydb file cd /var/lib/misc for i in $(seq 0001 1000); do useradd -P /var/lib/misc test$i; done make 6. verify users in berkeleydb is recognized id test1000 7. verify that 'getent passwd' and 'getenv group' calls correctly retrieve the entr fom verify that there's not as many open/close calls as there are entries in the DB files [ Where problems could occur ] To my understanding the historical reason for doing close-open for each line is to minimise possible resource usage and reduce the possibility of DB files getting stale if DB files get updated externally. Potential risks revolve around those two. In the former case, this could result in higher load on the system (modern hardware should be capable of handling that). In the latter case, lookups could fail and likely result in re-scans from the application. [ Other Info ] Debian bug and patch(not merged): https://bugs.debian.org/cgi- bin/bugreport.cgi?bug=1101371 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libnss-db/+bug/2121543/+subscriptions -- Mailing list: https://launchpad.net/~debcrafters-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~debcrafters-packages More help : https://help.launchpad.net/ListHelp
