2018-04-02 14:34 GMT+08:00 Minchan Kim <minc...@kernel.org>: > On Fri, Mar 30, 2018 at 12:04:07PM +0200, Greg Kroah-Hartman wrote: >> On Fri, Mar 30, 2018 at 10:29:21AM +0900, Minchan Kim wrote: >> > Hi Ganesh, >> > >> > On Fri, Mar 30, 2018 at 09:21:55AM +0800, Ganesh Mahendran wrote: >> > > 2018-03-29 14:54 GMT+08:00 Minchan Kim <minc...@kernel.org>: >> > > > binder_update_page_range needs down_write of mmap_sem because >> > > > vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless >> > > > it is set. However, when I profile binder working, it seems >> > > > every binder buffers should be mapped in advance by binder_mmap. >> > > > It means we could set VM_MIXEDMAP in binder_mmap time which is >> > > > already hold a mmap_sem as down_write so binder_update_page_range >> > > > doesn't need to hold a mmap_sem as down_write. >> > > > >> > > > Android suffers from mmap_sem contention so let's reduce mmap_sem >> > > > down_write. >> > > >> > > Hi, Minchan: >> > > >> > > It seems there is performance regression of this patch. >> > >> > You mean "This patch aims for solving performance regression" not "This >> > patch >> > makes performance regression"? >> > >> > > >> > > Do you have some test result of android app launch time or >> > > binderThroughput? >> > >> > Unfortunately, I don't have any number. The goal is to reduce the number of >> > call mmap_sem as write-side lock because it makes priority inversion of >> > threads >> > easily and that's one of clear part I spot that we don't need write-side >> > lock. >> >> Please always run the binderThroughput tests when making binder changes >> (there is a binder test suite in the CTS Android tests), as that ensures >> that you are not causing performance regressions as well as just normal >> bug regressions :) > > Thanks for the information. I didn't notice that such kinds of tests for > binder. I will keep it in mind. > > Today, I have setup the testing for my phone and found testing was very > fluctuating even without my patch. It might be not good with my test > skill. I emulated user's behavior with various touch event. With it, I open > various apps and play with them several times. Before starting the test, > I did "adb shell stop && adb shell start && echo 3 > /proc/sys/vm/drop_caches" > > Such 15% noise was very easy to make it. > > Ganesh, How did you measure? What's the stddev?
Hi, Minchan: Sorry for the late response, a little busy these days. :) We have our own test tools to measure app launch time, or you can use android systrace to get the app launch time. We tested your V1 patch: https://patchwork.kernel.org/patch/10312057/ and found app lunch time regression. I will use binderThroghput tool to test the patch today or tomorrow. Thanks. > Please let me know how you measure without noise so I'd like to reproduce > the result in my phone. > > I will do binderThroghput test, too. > >
