On Fri, Nov 21, 2008 at 04:13:38PM +0100, Eric Dumazet wrote: > [PATCH] fs: pipe/sockets/anon dentries should not have a parent > > Linking pipe/sockets/anon dentries to one root 'parent' has no functional > impact at all, but a scalability one. > > We can avoid touching a cache line at allocation stage (inside d_alloc(), no need > to touch root->d_count), but also at freeing time (in d_kill, decrementing d_count) > We avoid an expensive atomic_dec_and_lock() call on the root dentry. > > If we correct dnotify_parent() and inotify_d_instantiate() to take into account > a NULL d_parent, we can call d_alloc() with a NULL parent instead of root dentry. Sorry folks, but a NULL d_parent is a no-go from the VFS perspective, but you can set d_parent to the dentry itself which is the magic used for root of tree dentries. They should also be marked DCACHE_DISCONNECTED to make sure this is not unexpected. And this kind of stuff really needs to go through -fsdevel. -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
