Am Freitag, 29. Juni 2018, 02:52:16 CEST schrieb Jefferson Carpenter: > On 6/27/2018 1:18 PM, Richard Weinberger wrote: > > Am Mittwoch, 27. Juni 2018, 15:12:48 CEST schrieb Michal Hocko: > >> On Wed 27-06-18 13:29:05, Richard Weinberger wrote: > >>> On Wed, Jun 27, 2018 at 11:34 AM, Jefferson Carpenter > >>> <[email protected]> wrote: > >>>> Is there a way for a user process to mark memory as 'sensitive' or > >>>> 'non-sensitive' when it is allocated? That could allow it not to have > >>>> to be > >>>> zeroed before being allocated to another process. > >>> > >>> Isn't this what we have Meltdown and Spectre for? ;-) > >>> > >>> No, memory from the kernel is always zeroed. > >>> libc offers malloc() and calloc() for this purpose. > > Interesting. Let's say > > Process 1: > free(use_memory(malloc(1024))); > > Then Process 2: > malloc(1024); > > The physical RAM used to service Process 2's malloc call has to be > zeroed to prevent it from leaking data from Process 1. However, if > Process 1 could mark that memory as non-sensitive, then it would not > have to be zeroed, saving the time it takes to do that. However, this > would require at least a bit per memory page, so maybe it's not worth it.
Is this really a measurable overhead on your system? Do you have numbers? Thanks, //richard
