Messages in this thread |  | | Date | Mon, 12 Nov 2001 16:08:22 -0800 | From | Mike Fedyk <> | Subject | Re: File System Performance |
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On Mon, Nov 12, 2001 at 05:04:57PM -0700, Richard Gooch wrote: > Mike Fedyk writes: > > On Mon, Nov 12, 2001 at 12:59:54PM -0700, Richard Gooch wrote: > > > Here's an idea: add a "--compact" option to tar, so that it creates > > > *all* inodes (files and directories alike) in the base directory, and > > > then renames newly created entries to shuffle them into their correct > > > positions. That should limit the number of block groups that are used, > > > right? > > > > > > It would probably also be a good idea to do that for cp as well, so > > > that when I do a "cp -al" of a virgin kernel tree, I can keep all the > > > directory inodes together. It will make a cold diff even faster. > > > > I don't think that would help at all... With the current file/dir > > allocator it will choose a new block group for each directory no > > matter what the parent is... > > I thought the current implementation was that when creating a > directory, ext2fs searches forward from the block group the parent > directory is in, looking for a "relatively free" block group. So, a > number of successive calls to mkdir(2) with the same parent directory > will result in the child directories being in the same block group. > > So, creating the directory tree by creating directories in the base > directory and then shuffling should result in the directories be > spread out over a modest number of block groups, rather than a large > number. > > Addendum to my scheme: leaf nodes should be created in their > directories, not in the base directory. IOW, it's only directories > that should use this trick. > > Am I wrong in my understanding of the current algorithm? >
You are almost describing the new algo to a "T"...
It deals very well with fast growth, but not so well with slow growth, as mentioned in previous posts in this thread...
There is a lengthy thread in ext2-devel right now, if you read it it'll answer many of your questions.
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