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

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Message-ID: <582A972A.1010304@huawei.com>
Date:   Tue, 15 Nov 2016 13:03:38 +0800
From:   "Wangnan (F)" <wangnan0@...wei.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Alexei Starovoitov <ast@...com>, Zefan Li <lizefan@...wei.com>,
        He Kuang <hekuang@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        pi3orama <pi3orama@....com>, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 00/34] perf clang: Builtin clang and perfhook support



On 2016/11/15 12:57, Alexei Starovoitov wrote:
> On Mon, Nov 14, 2016 at 8:05 PM, Wang Nan <wangnan0@...wei.com> 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?

I can make it shorter by give it a better name or use a wrapper like

BPF_MAP(update_elem)

but the only thing I can't do is to make perfhook and in-kernel script
use a uniform name for these bpf_map functions, because
bpf_map_update_elem is already defined:

"static long (*bpf_map_update_elem)(void *, void *, void *, unsigned 
long) = (void *)2;\n"


>>    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.