From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Joel Fernandes <agnel.joel@gmail.com>
Cc: linux-rt-users@vger.kernel.org, fweisbec@gmail.com
Subject: Re: Question on clock drift with NO_HZ_FULL vs NO_HZ_IDLE
Date: Sun, 23 Feb 2014 08:38:49 -0800 [thread overview]
Message-ID: <20140223163849.GV4250@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAD=GYpaGnS=1A7z6AhtJ9KGH68NY4C5rGRXgfePm33he6s6YOw@mail.gmail.com>
On Sun, Feb 23, 2014 at 01:20:53AM -0600, Joel Fernandes wrote:
> Hi,
> After reading documentation, I follow that NO_HZ_FULL turns off the
> scheduling-clock interrupt on all except the boot CPU, where as
> NO_HZ_IDLE turns it off on all idle CPUs.
>
> I understand the period scheduling-clock interrupt is required to
> compensate for hardware oscillator drift. I believe that's why
> NO_HZ_FULL keeps it ON on atleast one CPU. That way the drift is
> compensated for.
>
> But, with NO_HZ_IDLE, all CPUs turn off interrupt during idle. Then
> how is the drift accounted for?
>
> CC'ing Paul as well for any guidance, thanks :)
The clock code fixes things up as needed when the first CPU returns
from idle.
Thanx, Paul
next prev parent reply other threads:[~2014-02-23 16:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-23 7:20 Question on clock drift with NO_HZ_FULL vs NO_HZ_IDLE Joel Fernandes
2014-02-23 16:38 ` Paul E. McKenney [this message]
2014-02-23 17:22 ` Joel Fernandes
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