linux-kernel - Re: [PATCH v7 perf, bpf-next 8/8] perf tools: synthesize PERF_RECORD

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Date:   Fri, 11 Jan 2019 19:23:43 +0000
From:   Song Liu <songliubraving@...com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     lkml <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "dsahern@...il.com" <dsahern@...il.com>
Subject: Re: [PATCH v7 perf, bpf-next 8/8] perf tools: synthesize
 PERF_RECORD_* for loaded BPF programs



> On Jan 11, 2019, at 10:44 AM, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> 
> Em Thu, Jan 10, 2019 at 04:19:33PM -0800, Song Liu escreveu:
>> This patch synthesize PERF_RECORD_KSYMBOL and PERF_RECORD_BPF_EVENT for
>> BPF programs loaded before perf-record. This is achieved by gathering
>> information about all BPF programs via sys_bpf.
>> 
>> Signed-off-by: Song Liu <songliubraving@...com>
>> ---
>> tools/perf/builtin-record.c |   6 ++
>> tools/perf/util/bpf-event.c | 205 ++++++++++++++++++++++++++++++++++++
>> tools/perf/util/bpf-event.h |   5 +
>> 3 files changed, 216 insertions(+)
>> 
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index deaf9b902094..88ea11d57c6f 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -41,6 +41,7 @@
>> #include "util/perf-hooks.h"
>> #include "util/time-utils.h"
>> #include "util/units.h"
>> +#include "util/bpf-event.h"
>> #include "asm/bug.h"
>> 
>> #include <errno.h>
>> @@ -1082,6 +1083,11 @@ static int record__synthesize(struct record *rec, bool tail)
>> 		return err;
>> 	}
>> 
>> +	err = perf_event__synthesize_bpf_events(tool, process_synthesized_event,
>> +						machine, opts);
>> +	if (err < 0)
>> +		pr_warning("Couldn't synthesize bpf events.\n");
>> +
> 
> There should be no warnings on older systems, I build a kernel and tools
> with your changes and then, before rebooting, I tried:
> 
> [root@...co ~]# perf record ls
> Couldn't synthesize bpf events.
> <SNIP>
> [root@...co ~]# uname -a
> Linux quaco 4.19.13-300.fc29.x86_64 #1 SMP Sat Dec 29 22:54:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
> [root@...co ~]#
> 
> At most this should be a pr_debug(), but then it should check if the
> system is bpf capable and if not only warn if the user explicitely asked
> for bpf events.

Thanks Arnaldo! I will fix it in the next version. 

Song