From: Keir Fraser <keir.fraser@eu.citrix.com>
To: Roger Cruz <rcruz@marathontechnologies.com>,
xen-devel <xen-devel@lists.xensource.com>
Subject: Re: Kernel printk timestamps and walltime drift
Date: Fri, 13 Jun 2008 21:31:18 +0100 [thread overview]
Message-ID: <C47897A6.19DDA%keir.fraser@eu.citrix.com> (raw)
In-Reply-To: <40B551BEDC7945419A5897958AB3947CB354D2@mtexch.marathontechnologies.com>
On 13/6/08 21:10, "Roger Cruz" <rcruz@marathontechnologies.com> wrote:
> The walltime appears to be generated from periodic timer ticks that
> update "xtime". These values have always been correct. Only the ones
> that get generated with the vprintk appear to slip when compared to this
> wall time.
Yes, sched_clock() can drift relative to wall time. It's an internal
monotonic timesource for the kernel, and if it drifts it doesn't usually
matter. It's not visible to user space. So, that explains your vprintk
timestamp drift. I hope it doesn't bother you too much. :-)
-- Keir
next prev parent reply other threads:[~2008-06-13 20:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <B99564216C25704085A82B41C46DD3427B060A@exchange.katana.local>
2008-06-13 17:53 ` Isolation and time Dan Magenheimer
2008-06-13 18:49 ` Kernel printk timestamps and walltime drift Roger Cruz
2008-06-13 19:47 ` Keir Fraser
2008-06-13 20:10 ` Roger Cruz
2008-06-13 20:31 ` Keir Fraser [this message]
2008-06-13 20:06 ` Dan Magenheimer
2008-06-13 21:05 ` Roger Cruz
2008-06-13 21:21 ` Dan Magenheimer
2008-06-13 21:36 ` Keir Fraser
2008-06-13 22:02 ` Roger Cruz
2008-06-13 22:09 ` Keir Fraser
2008-06-13 19:38 ` Isolation and time Keir Fraser
2008-06-14 2:20 ` Dan Magenheimer
2008-06-14 8:59 ` Keir Fraser
2008-06-14 15:16 ` Dan Magenheimer
2008-06-14 15:25 ` Keir Fraser
2008-07-01 0:22 ` Dan Magenheimer
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