On Wed, Oct 6, 2021 at 2:27 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 06.10.21 10:27, Michal Hocko wrote: > > On Tue 05-10-21 23:57:36, John Hubbard wrote: > > [...] > >> 1) Yes, just leave the strings in the kernel, that's simple and > >> it works, and the alternatives don't really help your case nearly > >> enough. > > > > I do not have a strong opinion. Strings are easier to use but they > > are more involved and the necessity of kref approach just underlines > > that. There are going to be new allocations and that always can lead > > to surprising side effects. These are small (80B at maximum) so the > > overall footpring shouldn't all that large by default but it can grow > > quite large with a very high max_map_count. There are workloads which > > really require the default to be set high (e.g. heavy mremap users). So > > if anything all those should be __GFP_ACCOUNT and memcg accounted. > > > > I do agree that numbers are just much more simpler from accounting, > > performance and implementation POV. > > +1 > > I can understand that having a string can be quite beneficial e.g., when > dumping mmaps. If only user space knows the id <-> string mapping, that > can be quite tricky. > > However, I also do wonder if there would be a way to standardize/reserve > ids, such that a given id always corresponds to a specific user. If we > use an uint64_t for an id, there would be plenty room to reserve ids ... > > I'd really prefer if we can avoid using strings and instead using ids. I wish it was that simple and for some names like [anon:.bss] or [anon:dalvik-zygote space] reserving a unique id would work, however some names like [anon:dalvik-/system/framework/boot-core-icu4j.art] are generated dynamically at runtime and include package name. Packages are constantly evolving, new ones are developed, names can change, etc. So assigning a unique id for these names is not really feasible. That leaves us with the central facility option, which as I described in my previous email would be prohibitive from performance POV (IPC every time we have a new name or want to convert id to name). I'm all for simplicity but the simple approach of using ids instead of names unfortunately would not work for our usecases. > > -- > Thanks, > > David / dhildenb >
