On Sat, 9 Jun 2012 00:41:03 +0300 "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > There's no reason to call rcu_barrier() on every deactivate_locked_super(). > We only need to make sure that all delayed rcu free inodes are flushed > before we destroy related cache. > > Removing rcu_barrier() from deactivate_locked_super() affects some > fas paths. E.g. on my machine exit_group() of a last process in IPC > namespace takes 0.07538s. rcu_barrier() takes 0.05188s of that time. What an unpleasant patch. Is final-process-exiting-ipc-namespace a sufficiently high-frequency operation to justify the change? I don't really understand what's going on here. Are you saying that there is some filesystem against which we run deactivate_locked_super() during exit_group(), and that this filesystem doesn't use rcu-freeing of inodes? The description needs this level of detail, please. The implementation would be less unpleasant if we could do the rcu_barrier() in kmem_cache_destroy(). I can't see a way of doing that without adding a dedicated slab flag, which would require editing all the filesystems anyway. (kmem_cache_destroy() already has an rcu_barrier(). Can we do away with the private rcu games in the vfs and switch to SLAB_DESTROY_BY_RCU?) -- 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
