Pavel Machek <[EMAIL PROTECTED]> writes: > 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...
So try to convince them to use the same cache daemon or the same shared cache manager library then. It isn't all that different from implementing a kernel interface that everyone is supposed to use. A cache manager daemon could sit and watch the free space on the disk every other second and start deleting the cached files (according to some LCU heuristics or whatever) whenever free space is getting low. To see if the original file is newer than the cached file, good old mtime can be used. I can't remember who right now, but someone mentioned a few problems with timestamps: 1. The resolutions is too low in current kernels, but that just means that someone(tm) needs to implement nanosecond timestamps in the kernel and for the filesystems. 2. Even nanosecond timestams may become to coarse in the future. One way of getting around this is to keep track of the latest timestamp written and make sure the next timestamp is one higher than the latest one. This way timestamps are always increasing, and I doubt that we can have modifications each nanosecond for a long time with the hardware available for the next ten years. 3. If time goes backwards beacuse somebody changes the clock, the caching (or makefile rules) can get confued. This is a hard one, but I actually we can use the doctors response "don't do that then". With NTP we can guarantee a monotonically increasing clock. I belive the kernel could give some assistance to make it easier to see if a file has been modified, I remember that a few suggestions were thrown around the last time Samba and dcache aliases were discussed on l-k. I definitely belive that kind of infrastructure belongs in the kernel. But the cache manager itself, no. /Christer -- "Just how much can I get away with and still go to heaven?" Freelance consultant specializing in device driver programming for Linux Christer Weinigel <[EMAIL PROTECTED]> http://www.weinigel.se