Offline Updates Performance Notes

So, after my epic 20+ minute offline update of 245 packages, last night I decided to look at some profiling numbers. All my testing was done using git master PackageKit (for the new strace support) on an otherwise unmodified Fedora 20 of a snapshot from last week. For the strace I chose to update two packages, otherwise the strace -tt output went maaaasive. Some salient points:

  • yum opens and closes the rpmdb 6692 times (that’s about 6690 more than it needs to) –we’re investigating why
  • fdatasync and fsync are killing us:


duration(ms) system call
805.749 fdatasync(17)
752.828 fsync(27)
658.659 fdatasync(9)
614.367 fdatasync(15)
598.182 fdatasync(33)
535.642 wait4(903, [{WIFEXITED(s) && WEXITSTATUS(s) =
423.247 wait4(911, [{WIFEXITED(s) && WEXITSTATUS(s) =
368.85 fsync(22)
309.556 stat(“/var/lib/yum/yumdb/g/gvfs-fuse-1.18.3-1.fc20-x86_64/checksum_type”
217.877 fdatasync(18)
179.002 close(23)

The full strace log is here (warning, huge) if you’re interested. I’ve got some other work to be doing today, but I’ll continue to work on this at the weekend.