On Tue, 5 Dec 2017 15:49:48 +0100 Michal Hocko <mho...@kernel.org> wrote:
> On Wed 29-11-17 09:17:34, Waiman Long 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. > > > > Signed-off-by: Waiman Long <long...@redhat.com> > > The patch still seems to be in the mmotm tree while it breaks > compilation. At least m32r defconfig complains with > mm/list_lru.c: In function 'list_lru_del': > mm/list_lru.c:141:2: error: implicit declaration of function 'prefetchw' > [-Werror=implicit-function-declaration] > prefetchw(item->prev); erp, I forgot to cc Stephen. > It also seems that there is no general agreement in the patch. Andrew, > do you plan to keep it? It's in wait-and-see mode.
