Hello, Daniel. On Wed, Oct 09, 2019 at 08:05:39AM +0200, Daniel Wagner wrote: > On Tue, Oct 08, 2019 at 06:04:59PM +0200, Uladzislau Rezki wrote: > > > so, we do not guarantee, instead we minimize number of allocations > > > with GFP_NOWAIT flag. For example on my 4xCPUs i am not able to > > > even trigger the case when CPU is not preloaded. > > > > > > I can test it tomorrow on my 12xCPUs to see its behavior there. > > > > > Tested it on different systems. For example on my 8xCPUs system that > > runs PREEMPT kernel i see only few GFP_NOWAIT allocations, i.e. it > > happens when we land to another CPU that was not preloaded. > > > > I run the special test case that follows the preload pattern and path. > > So 20 "unbind" threads run it and each does 1000000 allocations. As a > > result only 3.5 times among 1000000, during splitting, CPU was not > > preloaded thus, GFP_NOWAIT was used to obtain an extra object. > > > > It is obvious that slightly modified approach still minimizes allocations > > in atomic context, so it can happen but the number is negligible and can > > be ignored, i think. > > Thanks for doing the tests. In this case I would suggest to get rid of > the preempt_disable() micro optimization, since there is almost no > gain in doing so. Do you send a patch? :) > I can do it, for sure, in case you do not mind, since it was your initiative. Otherwise you can upload v2. -- Vlad Rezki
