Re: [PATCH 00/34] perf clang: Builtin clang and perfhook support

[Alexei Starovoitov]

On Mon, Nov 14, 2016 at 8:05 PM, Wang Nan <wangnan0@xxxxxxxxxx> wrote:
> This is version 2 of perf builtin clang patch series. Compare to v1,
> add an exciting feature: jit compiling perf hook functions. This
> features allows script writer report result through BPF map in a
> customized way.

looks great.

>   SEC("perfhook:record_start")
>   void record_start(void *ctx)
>   {
>         int perf_pid = getpid(), key = G_perf_pid;
>         printf("Start count, perfpid=%d\n", perf_pid);
>         jit_helper__map_update_elem(ctx, &GVALS, &key, &perf_pid, 0);

the name, I think, is too verbose.
Why not to keep them as bpf_map_update_elem
even for user space programs?

>   SEC("perfhook:record_end")
>   void record_end(void *ctx)
>   {
>         u64 key = -1, value;
>         while (!jit_helper__map_get_next_key(ctx, &syscall_counter, &key, &key)) {
>                 jit_helper__map_lookup_elem(ctx, &syscall_counter, &key, &value);
>                 printf("syscall %ld\tcount: %ld\n", (long)key, (long)value);

this loop will be less verbose as well.