From: john stultz <johnstul@us.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Mark Lord <lkml@rtr.ca>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [patch, v2.6.22-rc6] sys_time() speedup
Date: Tue, 26 Jun 2007 09:59:24 -0700 [thread overview]
Message-ID: <1182877164.1437.49.camel@localhost> (raw)
In-Reply-To: <20070626145825.GA31076@elte.hu>
On Tue, 2007-06-26 at 16:58 +0200, Ingo Molnar wrote:
> * Mark Lord <lkml@rtr.ca> wrote:
>
> > Ingo Molnar wrote:
> > >Subject: [patch] sys_time() speedup
> > >From: Ingo Molnar <mingo@elte.hu>
> > >
> > >improve performance of sys_time(). sys_time() returns time in seconds,
> > >but it does so by calling do_gettimeofday() and then returning the
> > >tv_sec portion of the GTOD time. But the data structure "xtime", which
> > >is updated by every timer/scheduler tick, already offers HZ granularity
> > >time.
> >
> > How well synchronized is xtime with real-time ?
>
> it's updated by every jiffy.
Well, NTP_INTERVAL_LENGTH to be specific which is every jiffie with one
exception: With dynticks this is a bit more complicated, and xtime is
updated only twice a second.
thanks
-john
prev parent reply other threads:[~2007-06-26 16:59 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-25 20:06 [patch, v2.6.22-rc6] sys_time() speedup Ingo Molnar
2007-06-25 21:09 ` Roman Zippel
2007-06-25 21:17 ` Jesper Juhl
2007-06-25 22:00 ` Roman Zippel
2007-06-25 22:20 ` Jesper Juhl
2007-06-25 22:49 ` Roman Zippel
2007-06-26 16:18 ` Ingo Molnar
2007-06-26 16:39 ` Roman Zippel
2007-06-26 16:49 ` Andrea Arcangeli
2007-06-26 17:13 ` Ray Lee
2007-06-27 0:15 ` Andrea Arcangeli
2007-06-26 17:08 ` Roman Zippel
2007-06-26 17:35 ` Andrew Morton
2007-06-25 22:15 ` Andrew Morton
2007-06-26 2:20 ` Stephen Rothwell
2007-06-26 15:26 ` Ingo Molnar
2007-06-26 17:14 ` Andrew Morton
2007-06-27 0:22 ` Andrea Arcangeli
2007-06-26 15:43 ` Andrea Arcangeli
2007-06-26 17:36 ` Andrew Morton
2007-06-25 22:02 ` Eric Dumazet
2007-06-26 0:22 ` Mark Lord
2007-06-26 14:58 ` Ingo Molnar
2007-06-26 16:59 ` john stultz [this message]
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