From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH 0/3] sched_clock updates
Date: Mon, 07 Jul 2008 14:16:49 -0400 [thread overview]
Message-ID: <20080707181649.942597764@goodmis.org> (raw)
Working with ftrace on linux-tip, I found a few problems with the sched_clock
code that is suppose to help an unstable TSC keep accurate time. The
problem I was seeing was on a box with a stable TSC. The time would
jump around a lot. One would think that code to help unstable TSC keep
time would not be a problem with a stable TSC.
The main change was the patch that handled the dynamic ticks. That was
the culprit of bein off by several jiffies.
With these patches applied, ftrace is quite a bit better with respect to time.
But there is still jumps that happen that do not happen with sched_clock.
I'm suspecting that the problems that still exist have more to do with
time updates or a drift between the TSC and the clock used for GTOD.
Anyway, enjoy,
-- Steve
next reply other threads:[~2008-07-07 18:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-07 18:16 Steven Rostedt [this message]
2008-07-07 18:16 ` [PATCH 1/3] sched_clock: record from last tick Steven Rostedt
2008-07-07 18:16 ` [PATCH 2/3] sched_clock: widen the max and min time Steven Rostedt
2008-07-07 18:16 ` [PATCH 3/3] sched_clock: stop maximum check on NO HZ Steven Rostedt
2008-07-16 11:14 ` Peter Zijlstra
2008-07-16 11:41 ` Steven Rostedt
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