On Tue, 5 Feb 2008 08:43:55 +0100 Christian Faulhammer <[EMAIL PROTECTED]> wrote: > > This will let package managers use a format other than VDB. A well > > designed replacement can shave a minute off cold cache command > > times. > > How much gain can be expected?
There're two common operations that're really really slow (because they need lots of filesystem access) using VDB: turning a pkg into a cat/pkg and finding all PROVIDEd packages. A redesigned format can, for example, make the former a single filesystem operation and the latter a single directory read. If you're looking for numbers, you can see very roughly how long a VDB load takes off cold cache using: echo 2 | sudo dd of=/proc/sys/vm/drop_caches find /var/db/pkg/ -type f -not -name 'environment.bz2' \ | xargs cat >/dev/null A different on-disk format could avoid 90% of those filesystem accesses for many operations. There's a more subtle issue with VDB and the scope of locking required by multithreaded implementations. This one's not an issue for interpreted languages, but it's a minor nuisance in places where there's no language-induced locking. > And what package managers will allow native_built_with_use? I doubt Portage will, since if someone's going to make changes to Portage that'd let it use something other than VDB, they've clearly got enough time to implement use deps as a side project, which would make built_with_use obsolete. Paludis would certainly implement it -- we've already got a redesigned on-disk db format that we use for tracking unpackaged packages, and repurposing that to handle ebuilds wouldn't be very hard. Incidentally, if anyone is still thinking that built_with_use is fine... It doesn't handle IUSE defaults, which means package managers have to store a hacked version of IUSE in VDB for EAPI 1. This isn't documented anywhere and is highly unobvious. -- Ciaran McCreesh
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