On Wed, 29 Nov 2017 09:17:34 -0500 Waiman Long <longman@xxxxxxxxxx> wrote: > The list_lru_del() function removes the given item from the LRU list. > The operation looks simple, but it involves writing into the cachelines > of the two neighboring list entries in order to get the deletion done. > That can take a while if the cachelines aren't there yet, thus > prolonging the lock hold time. > > To reduce the lock hold time, the cachelines of the two neighboring > list entries are now prefetched before acquiring the list_lru_node's > lock. > > Using a multi-threaded test program that created a large number > of dentries and then killed them, the execution time was reduced > from 38.5s to 36.6s after applying the patch on a 2-socket 36-core > 72-thread x86-64 system. Patch looks good. Can someone (Dave?) please explain why list_lru_del() supports deletion of an already list_empty(item)? This seems a rather dangerous thing to encourage. Use cases I can think of are: a) item is already reliably deleted, so why the heck was the caller calling list_lru_del() and b) item might be concurrently deleted by another thread, in which case the race loser is likely to hit a use-after-free. Is there a good use case here? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
