On Sun, Jul 22, 2012 at 07:58:42PM +0300, Uoti Urpala wrote: > Simon Paillard wrote: > > , I understand debian-installer ask dpkg not to fsync: > > > - Run dpkg with --force-unsafe-io during installation; syncing is > > This only affects one particular instance of syncing (which I think may > be useless anyway on normal ext4 after write+rename reliability was > improved in kernel commit 7d8f9f7d150dded7b68e61ca6403a1f166fb4edf). It > does not disable ALL disk sync operations in dpkg, like > installer/debootstrap use should. > > I tested installing and purging libqt4-dev and some dependencies on ext4 > (total 17 packages). > > With just force-unsafe-io in dpkg config: > aptitude install libqt4-dev: 16 seconds > aptitude --purge-unused purge libqt4-dev: 14 seconds > > eatmydata aptitude install libqt-dev: 4-5 seconds > eatmydata aptitude --purge-unused purge libqt4-dev: 4-5 seconds
You tested ext4. On btrfs, dpkg is around an order of magnitude slower, making using it without eatmydata a laughable idea. And that's on a filesystem whose features include: * transactions (so all dpkg processing could be done without a single fsync) * writeable snapshots (if you happen to get a power loss right during an untransacted dpkg run with eatmydata, all you need is a [re]boot with subvol=my_last_checkpoint) Thus, having an option to disable fsync in dpkg without unreliable LD_PRELOAD tricks would be great. -- Copyright and patents were never about promoting culture and innovations; from the very start they were legalized bribes to give the king some income and to let businesses get rid of competition. For some history, please read https://en.wikipedia.org/wiki/Statute_of_Monopolies_1623
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