On Wed, Oct 20, 2021 at 3:03 PM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > > Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> writes: > > > On Wed, Oct 20, 2021 at 11:09 AM Stanislav Fomichev <sdf@xxxxxxxxxx> wrote: > >> > >> On Wed, Oct 20, 2021 at 10:59 AM Andrii Nakryiko > >> <andrii.nakryiko@xxxxxxxxx> wrote: > >> > > >> > On Tue, Oct 12, 2021 at 8:29 AM Stanislav Fomichev <sdf@xxxxxxxxxx> wrote: > >> > > > >> > > On Mon, Oct 11, 2021 at 8:45 PM Andrii Nakryiko > >> > > <andrii.nakryiko@xxxxxxxxx> wrote: > >> > > > > >> > > > On Mon, Oct 11, 2021 at 11:24 PM Alexei Starovoitov <ast@xxxxxx> wrote: > >> > > > > > >> > > > > On 10/8/21 2:44 PM, Toke Høiland-Jørgensen wrote: > >> > > > > > > >> > > > > > Hmm, so introduce a new 'map_name_long' field, and on query the kernel > >> > > > > > will fill in the old map_name with a truncated version, and put the full > >> > > > > > name in the new field? Yeah, I guess that would work too! > >> > > > > > >> > > > > Let's start storing full map names in BTF instead. > >> > > > > Like we do already for progs. > >> > > > > Some tools already fetch full prog names this way. > >> > > > > >> > > > We do have those names in BTF. Each map has either corresponding VAR > >> > > > or DATASEC. The problem is that we don't know which. > >> > > > > >> > > > Are you proposing to add some extra "btf_def_type_id" field to specify > >> > > > BTF type ID of what "defines" the map (VAR or DATASEC)? That would > >> > > > work. Would still require UAPI and kernel changes, of course. > >> > > > > >> > > > The reason Toke and others were asking to preserve that object name > >> > > > prefix for .rodata/.data maps was different though, and won't be > >> > > > addressed by the above. Even if you know the BTF VAR/DATASEC, you > >> > > > don't know the "object name" associated with the map. And the kernel > >> > > > doesn't know because it's purely libbpf's abstraction. And sometimes > >> > > > that abstraction doesn't make sense (e.g., if we create a map that's > >> > > > pinned and reused from multiple BPF apps/objects). > >> > > > >> > > [..] > >> > > > >> > > > We do have BPF metadata that Stanislav added a while ago, so maybe we > >> > > > should just punt that problem to that? I'd love to have clean > >> > > > ".rodata" and ".data" names, of course. > >> > > > >> > > Are you suggesting we add some option to associate the metadata with > >> > > the maps (might be an option)? IIRC, the metadata can only be > >> > > associated with the progs right now. > >> > > >> > Well, maps have associated BTF fd, when they are created, no? So you > >> > can find all the same metadata for the map, no? > >> > >> I guess that's true, we can store this metadata in the map itself > >> using something like existing bpf_metadata_ prefix. > > > > We had a discussion during the inaugural BSC meeting about having a > > small set of "standardized" metadata strings. "owner" and > > "description" (or maybe "app" for "application name") were two that > > were clearly useful and generally useful. So if we update bpftool and > > other tooling to recognize bpf_metadata_owner and bpf_metadata_app and > > print them in some nice and meaningful way in bpftool output (in > > addition to general btf_metadata dump), it would be great. > > I like the idea of specifying some well-known metadata names, especially > if libbpf can auto-populate them if the user doesn't. > > Also, couldn't bpftool just print out all bpf_metadata_* fields? At > least in a verbose mode... Yes, bpftool dumps all bpf_metadata_* fields already. The point of converging on few common ones (say, bpf_metadata_owner and bpf_metadata_app) would allow all the tools to use consistent subset to display meaningful short info about a prog or map. Dumping all metadata fields for something like "bpf top" doesn't make sense. re: libbpf auto-populating some of them. It can populate "app" metadata from bpf_object's name, but we need to think through all the logistics carefully (e.g., not setting if user already specified that explicitly, etc). There is no way libbpf can know "owner" meta, though. > > -Toke >
