[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <1351094432.23327.42.camel@hornet>
Date: Wed, 24 Oct 2012 17:00:32 +0100
From: Pawel Moll <pawel.moll@....com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Amit Daniel Kachhap <amit.kachhap@...aro.org>,
Zhang Rui <rui.zhang@...el.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Jean Delvare <khali@...ux-fr.org>,
Guenter Roeck <linux@...ck-us.net>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...e.hu>, Jesper Juhl <jj@...osbits.net>,
Thomas Renninger <trenn@...e.de>,
Jean Pihet <jean.pihet@...oldbits.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>
Subject: Re: [RFC] Energy/power monitoring within the kernel
On Tue, 2012-10-23 at 18:43 +0100, Steven Rostedt wrote:
> > <...>212.673126: hwmon_attr_update: hwmon4 temp1_input 34361
> >
> > One issue with this is that some external knowledge is required to
> > relate a number to a processor core. Or maybe it's not an issue at all
> > because it should be left for the user(space)?
>
> If the external knowledge can be characterized in a userspace tool with
> the given data here, I see no issues with this.
Ok, fine.
> > TP_fast_assign(
> > memcpy(__entry->cpus, cpus, sizeof(struct cpumask));
>
> Copying the entire cpumask seems like overkill. Especially when you have
> 4096 CPU machines.
Uh, right. I didn't consider such use case...
> Perhaps making a field that can be a subset of cpus may be better. That
> way we don't waste the ring buffer with lots of zeros. I'm guessing that
> it will only be a group of cpus, and not a scattered list? Of course,
> I've seen boxes where the cpu numbers went from core to core. That is,
> cpu 0 was on core 1, cpu 1 was on core 2, and then it would repeat.
> cpu 8 was on core 1, cpu 9 was on core 2, etc.
>
> But still, this could be compressed somehow.
Sure thing. Or I could simply use cpumask_scnprintf() on the assign
stage and keep an already-formatted string. Or, as the cpumask per
sensor would be de-facto constant, I could assume keep only a pointer to
it. Will keep it in mind if this event was supposed to happen.
Thanks!
Paweł
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists