From: Ingo Molnar <mingo@elte.hu>
To: David Ahern <daahern@cisco.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-perf-users@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
acme@ghostprotocols.net, Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Paul Mackerras <paulus@samba.org>,
John Stultz <johnstul@us.ibm.com>, Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH 3/6] perf record: add time-of-day option
Date: Thu, 3 Mar 2011 09:51:48 +0100 [thread overview]
Message-ID: <20110303085148.GA16832@elte.hu> (raw)
In-Reply-To: <4D6E5413.6060500@cisco.com>
* David Ahern <daahern@cisco.com> wrote:
> > How does all that deal with CLOCK_REALTIME being affected by NTP and
> > settimeofday? Not really, as far as I can tell. It somehow works, but
> > that depends on the frequency of your event injection.
>
> It is sampled at some periodic rate to get NTP changes. Right now it is
> hardcoded at once an hour. The frequency option can be added to the
> --tod parameter.
As Thomas mentioned, we probably need something more complete than that.
Still your approach is obviously useful and i'd like to stress that explicitly. Have
you considered another related feature, feeding printk lines as special 'string
events' into the perf ringbuffer?
It would round up your scheme very nicely: that way you'd have a single, global,
GTOD-correlated event store/flow for basically every system event you might be
interested in. You could switch events (and tracepoints) on/off based on need,
controlling the type and rate of information in a very finegrained way.
If the printk approach works out i'd even suggest that such a facility would need a
separate tool within perf: 'perf syslog' or 'perf log'. It would heavily reuse
perf-script and other perf internal facilities, obviously - but you would not be
tied to any particular sub-tool implementation.
EDAC type events could feed into this as well, giving the tool a broader 'system
health' aspect as well, beyond the 'system performance analysis' aspect.
Thanks,
Ingo
next prev parent reply other threads:[~2011-03-03 8:52 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-28 3:52 [PATCH 0/6 v3] perf events: Add realtime clock event, time-of-day strings to script output David Ahern
2011-02-28 3:52 ` [PATCH 1/6] perf events: Introduce realtime clock event David Ahern
2011-02-28 3:52 ` [PATCH 2/6] perf events: plumbing for PERF_SAMPLE_READ and read_format David Ahern
2011-02-28 3:52 ` [PATCH 3/6] perf record: add time-of-day option David Ahern
2011-03-01 14:29 ` Peter Zijlstra
2011-03-01 14:35 ` David Ahern
2011-03-01 15:35 ` Peter Zijlstra
2011-03-01 15:41 ` David Ahern
2011-03-01 16:00 ` Peter Zijlstra
2011-03-01 16:09 ` David Ahern
2011-03-01 16:37 ` Peter Zijlstra
2011-03-01 16:45 ` David Ahern
2011-03-01 17:07 ` Arnaldo Carvalho de Melo
2011-03-01 17:09 ` Arnaldo Carvalho de Melo
2011-03-01 22:28 ` Peter Zijlstra
2011-03-01 22:35 ` David Ahern
2011-03-02 14:16 ` Thomas Gleixner
2011-03-02 14:28 ` David Ahern
2011-03-02 17:28 ` Thomas Gleixner
2011-03-03 14:29 ` David Ahern
2011-03-03 8:51 ` Ingo Molnar [this message]
2011-03-03 14:33 ` David Ahern
2011-02-28 3:52 ` [PATCH 4/6] perf script: dump software events too David Ahern
2011-03-01 14:09 ` Frederic Weisbecker
2011-03-01 14:18 ` David Ahern
2011-03-01 15:11 ` Frederic Weisbecker
2011-03-01 16:11 ` David Ahern
2011-03-01 16:24 ` Frederic Weisbecker
2011-03-01 16:49 ` Arnaldo Carvalho de Melo
2011-02-28 3:52 ` [PATCH 5/6] perf script: Prepend lines with time-of-day string David Ahern
2011-02-28 3:52 ` [PATCH 6/6] perf stat: treat realtime-clock as nsec counter David Ahern
2011-02-28 3:55 ` [PATCH 0/6 v3] perf events: Add realtime clock event, time-of-day strings to script output David Ahern
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