On Wed, Mar 07, 2007 at 08:16:14AM +0100, Eric Dumazet wrote: > Crazy ideas : (some readers are going to kill me) > > 1) Use the low order bit of f_path.dentry to say : this pointer is not a > pointer to a dentry but the inode pointer (with the low order bit set to 1) > > OR > > 2) file->f_path.dentry set to NULL for this special files (so that we dont > need to dput() and cache line ping pong the common dentry each time we > __fput() a pipe/socket.
No way on either one. f_path.dentry always beeing there is an assumption we make all over the place, and changing that would be a big regression for code qualityand reliability all over the place. Face it folks, memory is generally cheap, and we're not going to uglify huge amounts of code to shave of a little bit. [and that is only in reply to this one, the single dentry optimizations for epoll and friends are perfecltly fine from the high level view] > Same trick could be used for file->f_path.mnt, because there is a big SMP > cache line ping/pong to maintain a mnt_count on pipe/sockets mountpoint > while these file systems cannot be un-mounted) Same thing as above. We might do a hack to not refcount these vfsmounts, but we definitively want to keep the invariant of f_path.mnt never beeing NULL. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
