linux-kernel - Re: [PATCH] perf record: Add snapshot mode support for perf's regular events

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Date:	Tue, 24 Nov 2015 09:16:11 -0700
From:	David Ahern <dsahern@...il.com>
To:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:	Yunlong Song <yunlong.song@...wei.com>, a.p.zijlstra@...llo.nl,
	paulus@...ba.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
	wangnan0@...wei.com, namhyung@...nel.org, ast@...nel.org,
	masami.hiramatsu.pt@...achi.com, kan.liang@...el.com,
	adrian.hunter@...el.com, jolsa@...nel.org, bp@...en8.de,
	jean.pihet@...aro.org, rric@...nel.org, xiakaixu@...wei.com,
	hekuang@...wei.com
Subject: Re: [PATCH] perf record: Add snapshot mode support for perf's regular
 events

On 11/24/15 8:40 AM, Arnaldo Carvalho de Melo wrote:
> perf-record without his patch? yes, but with his patch it does:
>
>      __cmd_record()
>          for (;;)
>              record__mmap_read_all()
>                  record__write()
>                      perf_memory__write()
> 			event = (union perf_event *)(memory->start + memory->head + skip);
>                          if (event->header.type != PERF_RECORD_SAMPLE) {
>                              if (buf_to_file(rec, memory->start, memory->size,
>                          }
>
> I almost thought that I had been fooled by the difficulty to follow his
> patch and was forgetting that 'perf record' doesn't processes events,
> and hasn't done so for a very good reason: to reduce its impact on the
> observed workload, but that ain't so, no?

exactly. And I missed the above. Thanks for pointing that out.
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