Messages in this thread | | | Date | Wed, 9 Oct 2019 08:05:39 +0200 | From | Daniel Wagner <> | Subject | Re: [PATCH] mm: vmalloc: Use the vmap_area_lock to protect ne_fit_preload_node |
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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? :)
Thanks, Daniel
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