Re: silent semantic changes with reiser4

Pavel Machek
2004-08-31T22:07:26Z

Hi!

> > > However, that said, user space can trivially cache things in the
> > > filesystem, so while this may be a convenient feature, I think you should
> > > look at perhaps doing it in the _shell_ instead..
> >
> > That cache should disappear as soon as I need disk
> > space. I.e. userspace should never see -ENOSPC because of this kind of
> > caching. This need some kernel support. Ouch and cached file should
> > atomically go away as soon as main file changes, otherwise I do not
> > see how multiple processes could cooperate on caching...
>
> Well, what other projects have done is to just reserve a certain amount of
> disk for caching. See "ccache", which solves both of the above problems
> (it doesn't shrink the cache on ENOSPC, but reserving diskspace is
> accepted practice for things like this..)

Okay, that does work, it just is not really nice. Just as reserving
fixed ammount of space for disk cache is bad, reserving fixed ammount
of space for ccache (and similar) is bad. When there are few of such
caches, balancing between them starts to matter...
Pavel
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