On 12/19/05, Ryan Nordman <[EMAIL PROTECTED]> wrote: > I don't know how useful it'd be, I think it'd be great for getting you > familiar with the code base. It'd add a bit of overhead that's not really > that necessary, don't you think? Unless somebody really needs to know disk > usage *really* often. What's the case for doing this in kernel space > instead of just using the du utility?
Well, my first instinctive thought is that it might help thwart or postpone any potential persons thinking of switching to OpenSolaris+ZFS because of the so-called 'pooled storage' thinking. (ZFS has the ability to have multiple filesystems, even nested within each other, all sharing space from the same partition(s), and uses 'df' as opposed to du to find disk space, apparently df is 'cheaper' in terms of time used. Apparently, with ZFS, you can do a 'df' and suddenly know how much space is used and free in any one folder provided it's a seperate filesystem of it's own. A bit of an ... unusual abstraction to do things, but...) If done *correctly* in the kernel, I imagine it should be faster - du does what would be the equivilant of listing all the files in the directory and summing all the file sizes it gets (du -s) -- and it is affected by the user's permissions (if I have a directory in the directory i'm du-ing that I can't read, du will fail to account for the files within that directory). Last thing would be (hopefully) an ability to turn this thing on and off, and maybe to display the size of a folder's contents rather than the size of the directory's metadata in various utilities (if I 'ls -d' a directory, I usually get something like 2048B or 4096B depending on the number of files in there, although IIRC some big folders 'grow' to 16 KB, containing who knows what inside). > > On December 16, 2005 11:58 am, dannym wrote: > > > Hi, > > > > > > So I want to start writing a small plugin to get a feel for the > > > architecture... > > > As for what I thought would be a nice intro thing for me to write is: > > > > > > Adds a pseudo file "tree-contents-size" for directories. > > > Pseudo file contains the "du" starting from this directory. > > > > > > What it should do is cache some kind of "du"-like value per directory. > > > When you change a file size (or delete a file, add a file, ...) in the > > > dir or one of it's subdirs, it shall set a dirty flag on the value. > > > When the pseudo file is accessed, it shall calculate it anew, also > > > updating the subdirs' pseudo files if so needed, and store it actually > > > on disk... > > > (could also be updated periodically without anyone requesting it, but > > > that's just a detail) -- ~Mike - Just the crazy copy cat.
