linux-kernel - Re: [PATCH 28/31] perf probe: Init symbol as kprobe

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Date:	Wed, 2 Sep 2015 09:22:19 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
CC:	<mingo@...nel.org>, <ast@...mgrid.com>,
	<linux-kernel@...r.kernel.org>, <lizefan@...wei.com>,
	<pi3orama@....com>, Brendan Gregg <brendan.d.gregg@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	"David Ahern" <dsahern@...il.com>, He Kuang <hekuang@...wei.com>,
	Jiri Olsa <jolsa@...nel.org>, Kaixu Xia <xiakaixu@...wei.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 28/31] perf probe: Init symbol as kprobe



On 2015/9/2 4:11, Arnaldo Carvalho de Melo wrote:
> Em Sat, Aug 29, 2015 at 04:22:02AM +0000, Wang Nan escreveu:
>> Before this patch, add_perf_probe_events() init symbol maps only for
>> uprobe if the first 'struct perf_probe_event' passed to it is a uprobe
>> event. This is a trick because 'perf probe''s command line syntax
>> constrains the first elements of the probe_event arrays must be kprobes
>> if there is one kprobe there.
>>
>> However, with the incoming BPF uprobe support, that constrain is not
>> hold since 'perf record' will also probe on k/u probes through BPF
>> object, and is possible to pass an array with kprobe but the first
>> element is uprobe.
>>
>> This patch init symbol maps for kprobes even if all of events are
>> uprobes, because the extra cost should be small enough.
> Masami, are you Ok with this one?

I think he would be okay with it because it is his idea :)

Please refer to: http://lkml.kernel.org/n/558E5F42.1060705@hitachi.com

Thank you.
> - Arnaldo
>   
>> Signed-off-by: Wang Nan <wangnan0@...wei.com>
>> Cc: Alexei Starovoitov <ast@...mgrid.com>
>> Cc: Brendan Gregg <brendan.d.gregg@...il.com>
>> Cc: Daniel Borkmann <daniel@...earbox.net>
>> Cc: David Ahern <dsahern@...il.com>
>> Cc: He Kuang <hekuang@...wei.com>
>> Cc: Jiri Olsa <jolsa@...nel.org>
>> Cc: Kaixu Xia <xiakaixu@...wei.com>
>> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>> Cc: Namhyung Kim <namhyung@...nel.org>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> Cc: Zefan Li <lizefan@...wei.com>
>> Cc: pi3orama@....com
>> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
>> Link: http://lkml.kernel.org/n/1436445342-1402-39-git-send-email-wangnan0@huawei.com
>> ---
>>   tools/perf/util/probe-event.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>> index e720913..b94a8d7 100644
>> --- a/tools/perf/util/probe-event.c
>> +++ b/tools/perf/util/probe-event.c
>> @@ -2789,7 +2789,7 @@ int add_perf_probe_events(struct perf_probe_event *pevs, int npevs,
>>   {
>>   	int i, ret;
>>   
>> -	ret = init_symbol_maps(pevs->uprobes);
>> +	ret = init_symbol_maps(false);
>>   	if (ret < 0)
>>   		return ret;
>>   
>> -- 
>> 2.1.0


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