On Fri, Nov 20, 2020 at 10:39:14AM +0100, Ulrich Windl wrote: > Hi! > > journactl -b is quite fast to display the first lines, but when I want to see > the last lines, it's quite slow. The journal is on BtrFS that is on a > hardware RAID made from two SSDs, so the _filesystem_ should not be the > problem (actually it seems the journal is in tmpfs actually): > > ### done after being called before, so the file contents should be cached > anyway. > # time journalctl -b |wc -l > 2018589 > > real 0m21.890s > user 0m19.053s > sys 0m3.292s > > Reading all files to compare: > # time cat /run/log/journal/e766c8d06f144b1588487221640f55b5/* |wc -l > 3203984 > > real 0m0.729s > user 0m0.135s > sys 0m0.962s > > # df /run > Filesystem 1K-blocks Used Available Use% Mounted on > tmpfs 131889480 1664768 130224712 2% /run > > systemd-234-24.61.1.x86_64 from SLES15 SP2. >
How big are the journal files and how many are there? Can you re-run the command with SYSTEMD_LOG_LEVEL=debug and show the "mmap cache statistics" line? Would it be possible to run journalctl -b under `valgrind --tool=callgrind` and supply the callgrind.out? It would help identify where the CPU time is being spent on that set of logs. Regards, Vito Caputo _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
