linux-kernel - perf monitoring triggers Was: Re: [tip:perf/core] perf bench: Print both of prefaulted and no prefaulted results by default

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Date:	Sun, 12 Dec 2010 11:46:57 -0200
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Cc:	mingo@...hat.com, hpa@...or.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org, andi@...stfloor.org,
	a.p.zijlstra@...llo.nl, yakui.zhao@...el.com, fweisbec@...il.com,
	ling.ma@...el.com, rostedt@...dmis.org, miaox@...fujitsu.com,
	tglx@...utronix.de, mingo@...e.hu, acme@...stprotocols.net
Subject: perf monitoring triggers Was: Re: [tip:perf/core] perf bench:
	Print both of prefaulted and no prefaulted results by default

Em Sun, Dec 12, 2010 at 02:15:25AM +0900, Hitoshi Mitake escreveu:
> BTW, I found that measuring performance of prefaulted memcpy()
> with perf stat is difficult. Because current perf stat monitors
> whole execution of program or range of perf stat lifetime.

> If perf stat and monitored program can interact and work
> synchronously, it will be better.

> For example, if perf stat waits on the unix domain socket
> before create_perf_stat_counter() and monitored program wakes perf stat
> up through the socket, more fine grain monitoring will be possible.

> I imagine the execution will be like this:
> perf stat --wait-on /tmp/perf_wait perf bench mem memcpy --wake-up  
> /tmp/perf_wait

> --wait-on is imaginaly option of perf stat, and the way of waking up
> perf stat is left to monitored program (in this case, --wake-up is
> used for specifying the name of the socket).

> I'd like to implement such a option to perf stat, how do you think?

Looks interesting, and also interesting would be to be able to place
probes that would wake up it too, for unmodified binaries to have
something similar.

Other kinds of triggers may be to hook on syscalls and when some
expression matches, like connecting to host 1.2.3.4, start monitoring,
stop when the socket is closed, i.e. monitor a connection lifetime, etc.

I think it is worth pursuing and encourage you to work on it :-)

- Arnaldo
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