How is updatedb so much faster than find?
Here's a timed comparison between updatedb and a find command that does a seemingly similar task.
compare.sh
#!/usr/bin/env bash cmd="sudo updatedb" echo $cmd time eval $cmd cmd="sudo find / \ -fstype ext4 \ -not \( \ -path '/afs/*' -o \ -path '/net/*' -o \ -path '/sfs/*' -o \ -path '/tmp/*' -o \ -path '/udev/*' -o \ -path '/var/cache/*' -o \ -path '/var/lib/pacman/local/*' -o \ -path '/var/lock/*' -o \ -path '/var/run/*' -o \ -path '/var/spool/*' -o \ -path '/var/tmp/*' -o \ -path '/proc/*' \ \) &>/dev/null" echo $cmd time eval $cmd My /etc/updatedb.conf:
PRUNE_BIND_MOUNTS = "yes" PRUNEFS = "9p afs anon_inodefs auto autofs bdev binfmt_misc cgroup cifs coda configfs cpuset cramfs debugfs devpts devtmpfs ecryptfs exofs ftpfs fuse fuse.encfs fuse.sshfs fusectl gfs gfs2 hugetlbfs inotifyfs iso9660 jffs2 lustre mqueue ncpfs nfs nfs4 nfsd pipefs proc ramfs rootfs rpc_pipefs securityfs selinuxfs sfs shfs smbfs sockfs sshfs sysfs tmpfs ubifs udf usbfs vboxsf" PRUNENAMES = ".git .hg .svn" PRUNEPATHS = "/afs /net /sfs /tmp /udev /var/cache /var/lib/pacman/local /var/lock /var/run /var/spool /var/tmp" For the find command I just specified ext4 filesystem because that's the only filesystem updatedb should end up looking through. I didn't bother with the file extensions and I don't know how to exclude a bind mount from find but I don't have any. I also added an exclusion for '/proc' which it seems that updatedb ignores. I should have also ignored '/sys'.
If there'd be any difference I'd expect the find command to be a little faster since it's rules are a little simpler and it doesn't have to write to disk. Instead updatedb is much faster.
$ ./compare.sh sudo updatedb real 0m0.876s user 0m0.443s sys 0m0.273s sudo find / -fstype ext4 -not \( -path '/afs/*' -o -path '/net/*' -o -path '/sfs/*' -o -path '/tmp/*' -o -path '/udev/*' -o -path '/var/cache/*' -o -path '/var/lib/pacman/local/*' -o -path '/var/lock/*' -o -path '/var/run/*' -o -path '/var/spool/*' -o -path '/var/tmp/*' -o -path '/proc/*' \) &>/dev/null real 6m23.499s user 0m14.527s sys 0m10.993s What are they doing differently?
set -xto turn on printing of commands before they're executed, so you don't need the eval shenanigans.