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?
> This:
>
> # bpftool map
> 13: lpm_trie flags 0x1
> key 8B value 8B max_entries 1 memlock 4096B
> 14: lpm_trie flags 0x1
> key 20B value 8B max_entries 1 memlock 4096B
> 15: lpm_trie flags 0x1
> key 8B value 8B max_entries 1 memlock 4096B
> 16: lpm_trie flags 0x1
> key 20B value 8B max_entries 1 memlock 4096B
> 17: lpm_trie flags 0x1
> key 8B value 8B max_entries 1 memlock 4096B
> 18: lpm_trie flags 0x1
> key 20B value 8B max_entries 1 memlock 4096B
> 21: lpm_trie flags 0x1
> key 8B value 8B max_entries 1 memlock 4096B
> 22: lpm_trie flags 0x1
> key 20B value 8B max_entries 1 memlock 4096B
> 28: perf_event_array name __augmented_sys flags 0x0
> key 4B value 4B max_entries 8 memlock 4096B
> 29: array name syscalls flags 0x0
> key 4B value 1B max_entries 512 memlock 8192B
> 30: hash name pids_filtered flags 0x0
> key 4B value 1B max_entries 64 memlock 8192B
> #
> # bpftool map dump id 30
> [{
> "key": 26554,
> "value": true
> },{
> "key": 2592,
> "value": true
> }
> ]
> #
>
> Now is equivalent to:
>
> # bpftool map dump pids_filtered
Please do keep the current model of name val, IOW dump map *name* pids..
> [{
> "key": 26554,
> "value": true
> },{
> "key": 2592,
> "value": true
> }
> ]
> #
>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Cc: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
> cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Martin KaFai Lau <kafai@xxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Quentin Monnet <quentin.monnet@xxxxxxxxxxxxx>
> Cc: Song Liu <songliubraving@xxxxxx>
> Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
> Cc: Yonghong Song <yhs@xxxxxx>
> Link: https://lkml.kernel.org/n/tip-rrnxuhvety3j3rf0r9zlbfro@xxxxxxxxxxxxxx
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Please also update the bash completions and all the help/mans/docs.
