On Tue, Sep 10, 2024 at 08:42:54AM -0700, Paul E. McKenney wrote: > On Tue, Aug 20, 2024 at 05:59:35PM +0200, Uladzislau Rezki (Sony) wrote: > > Add a kvfree_rcu_barrier() function. It waits until all > > in-flight pointers are freed over RCU machinery. It does > > not wait any GP completion and it is within its right to > > return immediately if there are no outstanding pointers. > > > > This function is useful when there is a need to guarantee > > that a memory is fully freed before destroying memory caches. > > For example, during unloading a kernel module. > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> > > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> > > As a follow-on patch, once kvfree_rcu_barrier() is accepted into > mainline, should we add a call to kvfree_rcu_barrier() to the > rcu_barrier_throttled() function in kernel/rcu/tree.c? > > This would allow the do_rcu_barrier module parameter to be used to clear > out kfree_rcu() as well as call_rcu() work. This would be useful to > people running userspace benchmarks that cause the kernel to do a lot > of kfree_rcu() calls. Always good to avoid messing up the results from > the current run due to deferred work from the previous run. Even better > would be to actually account for the deferred work, but do_rcu_barrier > can help with that as well. ;-) > > Thoughts? > Makes sense. To be make sure that all objects are flushed. And as you mentioned it is good to have it for benchmarking as a return to a baseline point. One issue is probably a "name" which would be common for both: rcu_barrier() kvfree_rcu_barrier() i mean /sys/module/rcutree/parameters/do_rcu_barrier. From how i would see it, it is supposed to trigger just rcu_barrier() API. -- Uladzislau Rezki
