On Fri, Jul 31, 2020 at 01:48:55PM -0700, Paul E. McKenney wrote: > On Fri, Jul 31, 2020 at 01:38:34PM -0700, Andrew Morton wrote: > > On Thu, 30 Jul 2020 16:12:05 -0700 "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote: > > > > > So, may we add a GFP_ flag that will cause kmalloc() and friends to return > > > NULL when they would otherwise need to acquire their non-raw spinlock? > > > This avoids adding any overhead to the slab-allocator fastpaths, but > > > allows callback invocation to reduce cache misses without having to > > > restructure some existing callers of call_rcu() and potential future > > > callers of kfree_rcu(). > > > > We have eight free gfp_t bits so that isn't a problem. > > Whew!!! ;-) > > > Adding a test-n-branch to the kmalloc() fastpath may well be a concern. > > > > Which of mm/sl?b.c are affected? > > None of them, it turns out. The initial patch will instead directly > invoke __get_free_page(). So we could just leave sl?b.c alone. Isn't that spelled GFP_NOWAIT?
