From: Peter Zijlstra <peterz@infradead.org>
To: Chris Metcalf <cmetcalf@mellanox.com>
Cc: John Stultz <john.stultz@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Salman Qazi <sqazi@google.com>, Paul Turner <pjt@google.com>,
Tony Lindgren <tony@atomide.com>, Steven Miao <realmz6@gmail.com>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute cycle count
Date: Fri, 18 Nov 2016 15:50:46 +0100 [thread overview]
Message-ID: <20161118145046.GT3117@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <16b10c48-7caf-8097-e9a0-adca64c57773@mellanox.com>
On Fri, Nov 18, 2016 at 09:24:52AM -0500, Chris Metcalf wrote:
> I would think you would also unnecessarily accumulate small errors.
True..
> The x86 sched_clock() seems to purely scale the current TSC value,
> so what tile is doing is consistent with that, at least.
Right, this comes apart the moment TSC goes faster than 1GHz though.
Which might actually be the case, because then the mult-and-shift
reduces resolution and we'd wrap before the 64bit are done.
That would be something I ought to look at some time..
next prev parent reply other threads:[~2016-11-18 14:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 16:57 [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits Chris Metcalf
2016-11-16 18:04 ` John Stultz
2016-11-16 19:30 ` Chris Metcalf
2016-11-16 19:35 ` [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute cycle count Chris Metcalf
2016-11-16 19:59 ` John Stultz
2016-11-16 20:16 ` Chris Metcalf
2016-11-16 20:29 ` John Stultz
2016-11-16 20:31 ` John Stultz
2016-11-17 9:53 ` Peter Zijlstra
2016-11-17 20:00 ` Chris Metcalf
2016-11-18 10:34 ` Peter Zijlstra
2016-11-18 14:24 ` Chris Metcalf
2016-11-18 14:50 ` Peter Zijlstra [this message]
2016-11-16 19:40 ` [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits John Stultz
2016-11-16 19:45 ` John Stultz
2016-11-16 19:56 ` Chris Metcalf
2016-11-16 20:00 ` John Stultz
2016-11-16 20:30 ` Chris Metcalf
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