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From: Miroslav Lichvar <mlichvar@redhat.com>
To: John Stultz <john.stultz@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Richard Cochran <richardcochran@gmail.com>,
	Prarit Bhargava <prarit@redhat.com>
Subject: Re: [PATCH 0/3] timekeeping: Improved NOHZ frequency steering (v2)
Date: Tue, 8 Jul 2014 13:08:16 +0200	[thread overview]
Message-ID: <20140708110816.GB23173@localhost> (raw)
In-Reply-To: <CALAqxLUyCGJeYDwzXKN0zCBdmYuapo1iYJX4nvR7Sru+ySkesQ@mail.gmail.com>

On Mon, May 19, 2014 at 10:57:29AM -0700, John Stultz wrote:
> Another area we have to be careful with is there are still
> architectures (powerpc and ia64) which haven't switched from the old
> vsyscall rounding logic (CONFIG_GENERIC_TIME_VSYSCALL_OLD). In these
> cases we add up to 1ns of error each tick/update as we round up the
> sub-nanoseconds to ensure we don't see inconsistencies.  If the
> adjustment logic can't handle this, I don't want to regress those
> arches.

I spent some time trying to figure out a workaround for the nanosecond
rounding, but I didn't find anything that wouldn't complicate the mult
adjustment logic and bring back the problems which the direct division
approach is supposed to solve.

It seems it may be a while before the old vsyscalls are fixed. How
about including only the first two patches from this set for now?

Thanks,

-- 
Miroslav Lichvar

  parent reply	other threads:[~2014-07-08 11:08 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-17  0:56 [PATCH 0/3] timekeeping: Improved NOHZ frequency steering (v2) John Stultz
2014-05-17  0:56 ` [PATCH 1/3] [RFC] timekeeping: Rework frequency adjustments to work better w/ nohz John Stultz
2014-05-17  0:56 ` [PATCH 2/3] [RFC] timekeeping: Use cached ntp_tick_length when accumulating error John Stultz
2014-05-17  0:56 ` [PATCH 3/3] [RFC] timekeeping: Calculate freq adjustment directly John Stultz
2014-05-19 10:14 ` [PATCH 0/3] timekeeping: Improved NOHZ frequency steering (v2) Miroslav Lichvar
2014-05-19 17:57   ` John Stultz
2014-05-20 10:26     ` Miroslav Lichvar
2014-07-08 11:08     ` Miroslav Lichvar [this message]
2014-07-16  4:02       ` John Stultz
2014-07-16  6:59         ` Thomas Gleixner
2014-07-16 11:57         ` Miroslav Lichvar
2017-05-12 15:14         ` Miroslav Lichvar
2017-05-12 17:26           ` John Stultz
2017-05-17 15:03             ` Miroslav Lichvar

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