From: Matt Mackall <mpm@selenic.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: "Pekka Enberg" <penberg@cs.helsinki.fi>,
"Andi Kleen" <andi@firstfloor.org>,
"Wu Fengguang" <fengguang.wu@intel.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"Larry Woodman" <lwoodman@redhat.com>,
"Peter Zijlstra" <a.p.zijlstra@chello.nl>,
"Eduard - Gabriel Munteanu" <eduard.munteanu@linux360.ro>,
"Andrew Morton" <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
"KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>,
"Alexey Dobriyan" <adobriyan@gmail.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags
Date: Tue, 28 Apr 2009 12:42:08 -0500 [thread overview]
Message-ID: <1240940528.938.426.camel@calx> (raw)
In-Reply-To: <20090428093621.GD21085@elte.hu>
On Tue, 2009-04-28 at 11:36 +0200, Ingo Molnar wrote:
> I 'integrate' traces all the time to get summary counts. This series
> of dynamic events:
>
> allocation
> page count up
> page count up
> page count down
> page count up
> page count up
> page count up
> page count up
>
> integrates into: "page count is 6".
Perhaps you've failed calculus. The integral is 6 + C.
This is a critical distinction. Tracing is great for looking at changes,
but it completely falls down for static system-wide measurements because
it would require integrating from time=0 to get a meaningful summation.
That's completely useless for taking a measurement on a system that
already has an uptime of months.
Never mind that summing up page flag changes for every page on the
system since boot time through the trace interface is incredibly
wasteful given that we're keeping a per-page integral in the page tables
anyway.
Tracing is not the answer for everything.
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next prev parent reply other threads:[~2009-04-28 17:43 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-28 1:09 [PATCH 0/5] proc: export more page flags in /proc/kpageflags (take 4) Wu Fengguang
2009-04-28 1:09 ` [PATCH 1/5] pagemap: document clarifications Wu Fengguang
2009-04-28 7:11 ` Tommi Rantala
2009-04-28 1:09 ` [PATCH 2/5] pagemap: documentation 9 more exported page flags Wu Fengguang
2009-04-28 1:09 ` [PATCH 3/5] mm: introduce PageHuge() for testing huge/gigantic pages Wu Fengguang
2009-04-28 1:09 ` [PATCH 4/5] proc: kpagecount/kpageflags code cleanup Wu Fengguang
2009-04-28 1:09 ` [PATCH 5/5] proc: export more page flags in /proc/kpageflags Wu Fengguang
2009-04-28 6:55 ` Ingo Molnar
2009-04-28 7:40 ` Andi Kleen
2009-04-28 9:04 ` Pekka Enberg
2009-04-28 9:10 ` Andi Kleen
2009-04-28 9:15 ` Pekka Enberg
2009-04-28 9:15 ` Ingo Molnar
2009-04-28 9:19 ` Pekka Enberg
2009-04-28 9:25 ` Pekka Enberg
2009-04-28 9:36 ` Wu Fengguang
2009-04-28 9:36 ` Ingo Molnar
2009-04-28 9:57 ` Pekka Enberg
2009-04-28 10:10 ` KOSAKI Motohiro
2009-04-28 10:21 ` Pekka Enberg
2009-04-28 10:56 ` Ingo Molnar
2009-04-28 11:09 ` KOSAKI Motohiro
2009-04-28 12:42 ` Ingo Molnar
2009-04-28 11:03 ` Ingo Molnar
2009-04-28 17:42 ` Matt Mackall [this message]
2009-04-28 9:29 ` Ingo Molnar
2009-04-28 9:34 ` KOSAKI Motohiro
2009-04-28 9:38 ` Ingo Molnar
2009-04-28 9:55 ` Wu Fengguang
2009-04-28 10:11 ` KOSAKI Motohiro
2009-04-28 11:05 ` Ingo Molnar
2009-04-28 11:36 ` Wu Fengguang
2009-04-28 12:17 ` [rfc] object collection tracing (was: [PATCH 5/5] proc: export more page flags in /proc/kpageflags) Ingo Molnar
2009-04-28 13:31 ` Wu Fengguang
2009-05-12 13:01 ` Frederic Weisbecker
2009-05-17 13:36 ` Wu Fengguang
2009-05-17 13:55 ` Frederic Weisbecker
2009-05-17 14:12 ` Wu Fengguang
2009-05-18 11:44 ` KOSAKI Motohiro
2009-05-18 11:47 ` Wu Fengguang
2009-04-28 10:18 ` [PATCH 5/5] proc: export more page flags in /proc/kpageflags Andi Kleen
2009-04-28 8:33 ` Wu Fengguang
2009-04-28 9:24 ` Ingo Molnar
2009-04-28 18:11 ` Tony Luck
2009-04-28 18:34 ` Matt Mackall
2009-04-28 20:47 ` Tony Luck
2009-04-28 20:54 ` Andi Kleen
2009-04-28 20:59 ` Matt Mackall
2009-04-28 21:17 ` Andrew Morton
2009-04-28 21:49 ` Matt Mackall
2009-04-29 0:02 ` Robin Holt
2009-04-28 17:49 ` Matt Mackall
2009-04-29 8:05 ` Wu Fengguang
2009-04-29 19:13 ` Matt Mackall
2009-04-30 1:00 ` Wu Fengguang
2009-04-28 21:32 ` Andrew Morton
2009-04-28 22:46 ` Matt Mackall
2009-04-28 23:02 ` Andrew Morton
2009-04-28 23:31 ` Matt Mackall
2009-04-28 23:42 ` Andrew Morton
2009-04-28 23:55 ` Matt Mackall
2009-04-29 3:33 ` Wu Fengguang
2009-04-29 2:38 ` Wu Fengguang
2009-04-29 2:55 ` Andrew Morton
2009-04-29 3:48 ` Wu Fengguang
2009-04-29 5:09 ` Wu Fengguang
2009-04-29 4:41 ` Nathan Lynch
2009-04-29 4:50 ` Andrew Morton
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