DragonFly kernel List (threaded) for 2008-10
Re: HAMMER cleanup
Generally speaking I think hammer cleanup should only be automated
to the extent of being run as an overnight cron job.
I would prefer *not* to run hammer cleanup on boot as doing so just
hands us the same problem that background fsck has... it generates a
lot of disk I/O just at the wrong time. Even though the cleanup runs
for a limited period of time I still don't want it to run at boot.
Booting and shutdown are also the most dangerous times for disk
operations, mostly for laptops but also to some extent for desktops
and servers. These are the times where users try new configurations,
new kernels, where power fluctuations might be powering on a machine
or a UPS might be trying to shut it down. It is during these periods
when bad things are most likely to happen. We don't want to run
hammer cleanup during these periods.
I would like to keep a solution for laptops separate from the solution
for desktops. For desktops running overnight would do the trick. As
an alternative the cron can run it hourly... 'hammer cleanup' keeps track
of the time itself and by default will only do major work once a day,
even if run hourly. I dunno how far we should go for the 2.2 release.
Certainly it should at least be run overnight.
Laptops might need a 'cleanup' button. I just don't know when the best
time to run hammer cleanup would be, or for how long. Desktops might
make do with an hourly poke.