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From: "Luck, Tony" <tony.luck@intel.com>
To: "john stultz" <johnstul@us.ibm.com>, <bob.picco@hp.com>
Cc: "Steven Rostedt" <rostedt@goodmis.org>,
	"LKML" <linux-kernel@vger.kernel.org>,
	"Ingo Molnar" <mingo@elte.hu>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Peter Zijlstra" <a.p.zijlstra@chello.nl>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Mathieu Desnoyers" <mathieu.desnoyers@polymtl.ca>,
	"Gregory Haskins" <ghaskins@novell.com>,
	"Arnaldo Carvalho de Melo" <acme@ghostprotocols.net>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Tim Bird" <tim.bird@am.sony.com>,
	"Sam Ravnborg" <sam@ravnborg.org>,
	"Frank Ch. Eigler" <fche@redhat.com>,
	"Steven Rostedt" <srostedt@redhat.com>
Subject: RE: [RFC PATCH 13/22 -v2] handle accurate time keeping over longdelays
Date: Thu, 10 Jan 2008 13:33:09 -0800	[thread overview]
Message-ID: <1FE6DD409037234FAB833C420AA843EC48842F@orsmsx424.amr.corp.intel.com> (raw)
In-Reply-To: <1199996959.6108.18.camel@localhost.localdomain>

> If you noticed in my email, the fix for ppc was a bit easier, as it has
> only a 64bit counter that is quite unlikely to wrap twice between calls
> to update_wall_time().

"quite unlikely" ...

Hmmm just how fast are you driving the clocks on your ppc?  Even at 100GHz
It is almost SIX YEARS between wrap-arounds of a 64-bit counter.
Perhaps you could just have a cron job that forces a call to update_wall_time()
every January 1st, rather than add extra code overhead to a hot path :-) ?

But I agree that narrower counters are a problem.

-Tony

  parent reply	other threads:[~2008-01-10 21:36 UTC|newest]

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-09 23:29 [RFC PATCH 00/22 -v2] mcount and latency tracing utility -v2 Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 01/22 -v2] Add basic support for gcc profiler instrumentation Steven Rostedt
2008-01-10 18:19   ` Jan Kiszka
2008-01-10 19:54     ` Steven Rostedt
2008-01-10 23:02     ` Steven Rostedt
2008-01-10 18:28   ` Sam Ravnborg
2008-01-10 19:10     ` Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 02/22 -v2] Annotate core code that should not be traced Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 03/22 -v2] x86_64: notrace annotations Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 04/22 -v2] add notrace annotations to vsyscall Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 05/22 -v2] add notrace annotations for NMI routines Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 06/22 -v2] mcount based trace in the form of a header file library Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 07/22 -v2] tracer add debugfs interface Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 08/22 -v2] mcount tracer output file Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 09/22 -v2] mcount tracer show task comm and pid Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 10/22 -v2] Add a symbol only trace output Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 11/22 -v2] Reset the tracer when started Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 12/22 -v2] separate out the percpu date into a percpu struct Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 13/22 -v2] handle accurate time keeping over long delays Steven Rostedt
2008-01-10  0:00   ` john stultz
2008-01-10  0:09     ` Steven Rostedt
2008-01-10 19:54     ` Tony Luck
2008-01-10 20:15       ` Steven Rostedt
2008-01-10 20:41         ` john stultz
2008-01-10 20:29       ` john stultz
2008-01-10 20:42         ` Mathieu Desnoyers
2008-01-10 21:25           ` john stultz
2008-01-10 22:00             ` Mathieu Desnoyers
2008-01-10 22:40               ` Steven Rostedt
2008-01-10 22:51               ` john stultz
2008-01-10 23:05                 ` john stultz
2008-01-10 21:33         ` Luck, Tony [this message]
2008-01-10  0:19   ` john stultz
2008-01-10  0:25     ` Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 14/22 -v2] time keeping add cycle_raw for actual incrementation Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 15/22 -v2] initialize the clock source to jiffies clock Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 16/22 -v2] add get_monotonic_cycles Steven Rostedt
2008-01-10  3:28   ` Daniel Walker
2008-01-15 21:46   ` Mathieu Desnoyers
2008-01-15 22:01     ` Steven Rostedt
2008-01-15 22:03       ` Steven Rostedt
2008-01-15 22:08       ` Mathieu Desnoyers
2008-01-16  1:38         ` Steven Rostedt
2008-01-16  3:17           ` Mathieu Desnoyers
2008-01-16 13:17             ` Steven Rostedt
2008-01-16 14:56               ` Mathieu Desnoyers
2008-01-16 15:06                 ` Steven Rostedt
2008-01-16 15:28                   ` Mathieu Desnoyers
2008-01-16 15:58                     ` Steven Rostedt
2008-01-16 17:00                       ` Mathieu Desnoyers
2008-01-16 17:49                         ` Mathieu Desnoyers
2008-01-16 19:43                         ` Steven Rostedt
2008-01-16 20:17                           ` Mathieu Desnoyers
2008-01-16 20:45                             ` Tim Bird
2008-01-16 20:49                             ` Steven Rostedt
2008-01-17 20:08                             ` Steven Rostedt
2008-01-17 20:37                               ` Frank Ch. Eigler
2008-01-17 21:03                                 ` Steven Rostedt
2008-01-18 22:26                                   ` Mathieu Desnoyers
2008-01-18 22:49                                     ` Steven Rostedt
2008-01-18 23:19                                       ` Mathieu Desnoyers
2008-01-19  3:36                                         ` Frank Ch. Eigler
2008-01-19  3:55                                           ` Steven Rostedt
2008-01-19  4:23                                             ` Frank Ch. Eigler
2008-01-19 15:29                                               ` Mathieu Desnoyers
2008-01-19  3:32                                       ` Frank Ch. Eigler
2008-01-16 18:01                       ` Tim Bird
2008-01-16 22:36                 ` john stultz
2008-01-16 22:51                   ` john stultz
2008-01-16 23:33                     ` Steven Rostedt
2008-01-17  2:28                       ` john stultz
2008-01-17  2:40                         ` Mathieu Desnoyers
2008-01-17  2:50                           ` Mathieu Desnoyers
2008-01-17  3:02                             ` Steven Rostedt
2008-01-17  3:21                             ` Paul Mackerras
2008-01-17  3:39                               ` Steven Rostedt
2008-01-17  4:22                                 ` Mathieu Desnoyers
2008-01-17  4:25                                 ` Mathieu Desnoyers
2008-01-17  4:14                               ` Mathieu Desnoyers
2008-01-17 15:22                                 ` Steven Rostedt
2008-01-17 17:46                                 ` Linus Torvalds
2008-01-17  2:51                           ` Steven Rostedt
2008-01-16 23:39                     ` Mathieu Desnoyers
2008-01-16 23:50                       ` Steven Rostedt
2008-01-17  0:36                         ` Steven Rostedt
2008-01-17  0:33                       ` john stultz
2008-01-17  2:20                         ` Mathieu Desnoyers
2008-01-17  1:03                       ` Linus Torvalds
2008-01-17  1:35                         ` Mathieu Desnoyers
2008-01-17  2:20                       ` john stultz
2008-01-17  2:35                         ` Mathieu Desnoyers
2008-01-09 23:29 ` [RFC PATCH 17/22 -v2] Add timestamps to tracer Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 18/22 -v2] Sort trace by timestamp Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 19/22 -v2] speed up the output of the tracer Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 20/22 -v2] Add latency_trace format tor tracer Steven Rostedt
2008-01-10  3:41   ` Daniel Walker
2008-01-09 23:29 ` [RFC PATCH 21/22 -v2] Split out specific tracing functions Steven Rostedt
2008-01-09 23:29 ` [RFC PATCH 22/22 -v2] Trace irq disabled critical timings Steven Rostedt
2008-01-10  3:58   ` Daniel Walker
2008-01-10 14:45     ` Steven Rostedt

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