On Wed, 7 Aug 2019 16:45:30 -0400 Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > On Wed, Aug 07, 2019 at 01:04:02PM -0700, Andrew Morton wrote: > > On Wed, 7 Aug 2019 13:15:54 -0400 "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx> wrote: > > > > > In Android, we are using this for the heap profiler (heapprofd) which > > > profiles and pin points code paths which allocates and leaves memory > > > idle for long periods of time. This method solves the security issue > > > with userspace learning the PFN, and while at it is also shown to yield > > > better results than the pagemap lookup, the theory being that the window > > > where the address space can change is reduced by eliminating the > > > intermediate pagemap look up stage. In virtual address indexing, the > > > process's mmap_sem is held for the duration of the access. > > > > So is heapprofd a developer-only thing? Is heapprofd included in > > end-user android loads? If not then, again, wouldn't it be better to > > make the feature Kconfigurable so that Android developers can enable it > > during development then disable it for production kernels? > > Almost all of this code is already configurable with > CONFIG_IDLE_PAGE_TRACKING. If you disable it, then all of this code gets > disabled. > > Or are you referring to something else that needs to be made configurable? Yes - the 300+ lines of code which this patchset adds! The impacted people will be those who use the existing idle-page-tracking feature but who will not use the new feature. I guess we can assume this set is small...
