Em Fri, Mar 15, 2019 at 07:41:35PM +0000, Quentin Monnet escreveu:
> 2019-03-15 12:16 UTC-0700 ~ Jakub Kicinski <[email protected]>
> > On Fri, 15 Mar 2019 15:41:41 -0300, Arnaldo Carvalho de Melo wrote:
> > > While developing 'perf trace' and looking at BPF maps it puts in place I
> > > noticed that one needs to first use 'bpftool map' to lookup a map id to
> > > then use 'bpftool map dump map id <map-id-looked-up>'.
> > >
> > > This is needed because everytime we restart 'perf trace' the map IDs
> > > gets changed so we need to do the ID lookup again.
> > >
> > > To speed up this sequence, allow specifying just the map name, look up
> > > its ID and then use the existing routines as if the user had provided
> > > the map id.
> >
> > I can see how it could be useful for quick debug. Names are not
> > guaranteed to be unique, though, do you not care about potential
> > duplicates?
> >
>
> Jakub beat me to it by a few seconds :). I discussed possible workarounds on
> that point with him though, so here are my two cents. I see two options:
> first one would be to return the ids of, and then dump info about all maps
> having that name. The second one would be to simply return an error if
> duplicate names are found.
>
> We agreed that returning an error if there are duplicates is probably the
> best way to go, because dealing with several maps for anything else than
> "bpftool map show" would be problematic (clearly, we don't want to update
> all maps with a given name at once). Of course if you have other
> suggestions, feel free to propose :).
So, if there are dups, just tell that and print the ids, i.e. the
following, for any 'bpf map' command that finds dups, except for this
one:
[root@quaco ~]# bpftool map list pids_filtered
45: hash name pids_filtered flags 0x0
key 4B value 1B max_entries 64 memlock 8192B
90: hash name pids_filtered flags 0x0
key 4B value 80B max_entries 512 memlock do-the-mathB
[root@quaco ~]#
I.e. if there are multiple 'pids_filtered' maps, the output for, say,
'dump' would be:
[root@quaco ~]# bpftool map dump pids_filtered
There are multiple maps with this name, use 'bpftool map dump id NR' to
disambiguate:
-------------------------------------------------------------------------------------
45: hash name pids_filtered flags 0x0
key 4B value 1B max_entries 64 memlock 8192B
90: hash name pids_filtered flags 0x0
key 4B value 80B max_entries 512 memlock do-the-mathB
[root@quaco ~]#
- Arnaldo
