On Mon, Oct 11, 2021 at 8:00 PM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > On Mon, Oct 11, 2021 at 06:20:25PM -0700, Suren Baghdasaryan wrote: > > On Mon, Oct 11, 2021 at 6:18 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > > > > > On Mon, Oct 11, 2021 at 1:36 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > > > On Fri 08-10-21 13:58:01, Kees Cook wrote: > > > > > - Strings for "anon" specifically have no required format (this is good) > > > > > it's informational like the task_struct::comm and can (roughly) > > > > > anything. There's no naming convention for memfds, AF_UNIX, etc. Why > > > > > is one needed here? That seems like a completely unreasonable > > > > > requirement. > > > > > > > > I might be misreading the justification for the feature. Patch 2 is > > > > talking about tools that need to understand memeory usage to make > > > > further actions. Also Suren was suggesting "numbering convetion" as an > > > > argument against. > > > > > > > > So can we get a clear example how is this being used actually? If this > > > > is just to be used to debug by humans than I can see an argument for > > > > human readable form. If this is, however, meant to be used by tools to > > > > make some actions then the argument for strings is much weaker. > > > > > > The simplest usecase is when we notice that a process consumes more > > > memory than usual and we do "cat /proc/$(pidof my_process)/maps" to > > > check which area is contributing to this growth. The names we assign > > > to anonymous areas are descriptive enough for a developer to get an > > > idea where the increased consumption is coming from and how to proceed > > > with their investigation. > > > There are of course cases when tools are involved, but the end-user is > > > always a human and the final report should contain easily > > > understandable data. > > > > > > IIUC, the main argument here is whether the userspace can provide > > > tools to perform the translations between ids and names, with the > > > kernel accepting and reporting ids instead of strings. Technically > > > it's possible, but to be practical that conversion should be fast > > > because we will need to make name->id conversion potentially for each > > > mmap. On the consumer side the performance is not as critical, but the > > > fact that instead of dumping /proc/$pid/maps we will have to parse the > > > file, do id->name conversion and replace all [anon:id] with > > > [anon:name] would be an issue when we do that in bulk, for example > > > when collecting system-wide data for a bugreport. > > Is that something you need to do client-side? Or could the bug tool > upload the userspace-maintained name:ids database alongside the > /proc/pid/maps dump for external processing? You can generate a bugreport and analyze it locally or submit it as an attachment to a bug for further analyzes. Sure, we can attach the id->name conversion table to the bugreport but either way, some tool would have to post-process it to resolve the ids. If we are not analyzing the results immediately then that step can be postponed and I think that's what you mean? If so, then yes, that is correct.
