On Fri, 12 Mar 2010, Guillem Jover wrote: > Right, I didn't see much degradation on ext3, or I'd probably would have > considered doing alternative changes instead. I'll be testing on a > slower box with ext3 to see how it behaves there though.
My main disk is SSD so I didn't notice immediately either. > > Other possibility would be to use the loop afterwards to reopen all > > installed files and call fsync() on them. The disadvantage of sync() is > > obviously when unrelated disk activity happens in parallel to dpkg, it > > will have to wait more due to this. > > Neither of those are good replacements, as the fsync() must be done before > the rename(), as we want the guarantee that there's always a valid file in > place in case of a crash, either the old or the new, which dpkg should be > able to discern and roll-back if needed on reexecution. > Doing a sync afterwards might only guarantee the package is not wrongly > marked as properly installed if there's a system crash, but that's it. That's what matters IMO. > And in such case there's a high probability the files will be > zero-length, which would be pretty bad for example Essential packages. So let's do the fsync only for essential packages? It's a good compromise IMO. > In addition POSIX does not guarantee sync() will wait until the writes > have finished (only Linux seems to be doing that though). True, not sure what other systems are doing though. Cheers, -- Raphaël Hertzog Like what I do? Sponsor me: http://ouaza.com/wp/2010/01/05/5-years-of-freexian/ My Debian goals: http://ouaza.com/wp/2010/01/09/debian-related-goals-for-2010/ -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/20100312220418.ga4...@rivendell
