On Sun, 16 Sep 2007, Jörn Engel wrote: > > My approach is to have one for mount points and ramfs/tmpfs/sysfs/etc. > which are pinned for their entire lifetime and another for regular > files/inodes. One could take a three-way approach and have > always-pinned, often-pinned and rarely-pinned. > > We won't get never-pinned that way. That sounds pretty good. The problem, of course, is that most of the time, the actual dentry allocation itself is done before you really know which case the dentry will be in, and the natural place for actually giving the dentry lifetime hint is *not* at "d_alloc()", but when we "instantiate" it with d_add() or d_instantiate(). But it turns out that most of the filesystems we care about already use a special case of "d_add()" that *already* replaces the dentry with another one in some cases: "d_splice_alias()". So I bet that if we just taught "d_splice_alias()" to look at the inode, and based on the inode just re-allocate the dentry to some other slab cache, we'd already handle a lot of the cases! And yes, you'd end up with the reallocation overhead quite often, but at least it would now happen only when filling in a dentry, not in the (*much* more critical) cached lookup path. Linus - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
