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. Thanks.
