On Fri 14-09-18 03:33:28, Jann Horn wrote: > On Wed, Sep 12, 2018 at 10:43 PM prakash.sangappa > <prakash.sangappa@xxxxxxxxxx> wrote: > > On 05/09/2018 04:31 PM, Dave Hansen wrote: > > > On 05/07/2018 06:16 PM, prakash.sangappa wrote: > > >> It will be /proc/<pid>/numa_vamaps. Yes, the behavior will be > > >> different with respect to seeking. Output will still be text and > > >> the format will be same. > > >> > > >> I want to get feedback on this approach. > > > I think it would be really great if you can write down a list of the > > > things you actually want to accomplish. Dare I say: you need a > > > requirements list. > > > > > > The numa_vamaps approach continues down the path of an ever-growing list > > > of highly-specialized /proc/<pid> files. I don't think that is > > > sustainable, even if it has been our trajectory for many years. > > > > > > Pagemap wasn't exactly a shining example of us getting new ABIs right, > > > but it sounds like something along those is what we need. > > > > Just sent out a V2 patch. This patch simplifies the file content. It > > only provides VA range to numa node id information. > > > > The requirement is basically observability for performance analysis. > > > > - Need to be able to determine VA range to numa node id information. > > Which also gives an idea of which range has memory allocated. > > > > - The proc file /proc/<pid>/numa_vamaps is in text so it is easy to > > directly view. > > > > The V2 patch supports seeking to a particular process VA from where > > the application could read the VA to numa node id information. > > > > Also added the 'PTRACE_MODE_READ_REALCREDS' check when opening the > > file /proc file as was indicated by Michal Hacko > > procfs files should use PTRACE_MODE_*_FSCREDS, not PTRACE_MODE_*_REALCREDS. Out of my curiosity, what is the semantic difference? At least kernel_move_pages uses PTRACE_MODE_READ_REALCREDS. Is this a bug? -- Michal Hocko SUSE Labs
