On Fri, Mar 02, 2018 at 03:34:52PM -0800, Andrew Morton wrote: > On Tue, 27 Feb 2018 05:06:43 -0800 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > On Tue, Feb 27, 2018 at 11:22:59AM +0100, Uladzislau Rezki (Sony) wrote: > > > During finding a suitable hole in the vmap_area_list > > > there is an explicit rescheduling check for latency reduction. > > > We do it, since there are workloads which are sensitive for > > > long (more than 1 millisecond) preemption off scenario. > > > > I understand your problem, but this is a horrid solution. If it takes > > us a millisecond to find a suitable chunk of free address space, something > > is terribly wrong. On a 3GHz CPU, that's 3 million clock ticks! > > Yup. > > > I think our real problem is that we have no data structure that stores > > free VA space. We have the vmap_area which stores allocated space, but no > > data structure to store free space. > > I wonder if we can reuse free_vmap_cache as a quick fix: if > need_resched(), point free_vmap_cache at the current rb_node, drop the > lock, cond_resched, goto retry? > It sounds like we can. But there is a concern if that potentially can introduce a degrade of search time due to changing a starting point for our search. -- Vlad Rezki -- 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>
