2018-03-30 9:29 GMT+08:00 Minchan Kim <minc...@kernel.org>: > 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"?
After applying this patch in our devices, app launch time increases about 15% in average. "This patch makes performance regression", yes, from the results, it is like this. I will do more test of this patch. > >> >> 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. > > Thanks.
