From: Ingo Molnar <mingo@kernel.org>
To: John Stultz <john.stultz@linaro.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Dave Jones <davej@codemonkey.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Richard Cochran <richardcochran@gmail.com>,
Prarit Bhargava <prarit@redhat.com>,
Stephen Boyd <sboyd@codeaurora.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 02/12] clocksource: Simplify logic around clocksource wrapping saftey margins
Date: Sat, 7 Mar 2015 10:22:15 +0100 [thread overview]
Message-ID: <20150307092215.GC30888@gmail.com> (raw)
In-Reply-To: <1425696603-16878-3-git-send-email-john.stultz@linaro.org>
* John Stultz <john.stultz@linaro.org> wrote:
> The clocksource logic has a number of places where we try to
> include a safety margin. Most of these are 12% safety margins,
> but they are inconsistently applied and sometimes are applied
> on top of each other.
>
> Additionally, in the previous patch, we corrected an issue
> where we unintentionally in effect created a 50% saftey margin,
> which these 12.5% margins where then added to.
>
> So to siplify the logic here, this patch removes the various
Typo.
> 12.5% margins, and consolidates adding the margin in one place:
> clocks_calc_max_nsecs().
>
> Addtionally, Linus prefers a 50% safety margin, as it allows
> bad clock values to be more easily caught. This should really
> have no net effect, due to the corrected issue earlier which
> caused greater then 50% margins to be used w/o issue.
>
> Cc: Dave Jones <davej@codemonkey.org.uk>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <sboyd@codeaurora.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Acked-by: Stephen Boyd <sboyd@codeaurora.org> (for sched_clock.c bit)
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> kernel/time/clocksource.c | 26 ++++++++++++--------------
> kernel/time/sched_clock.c | 4 ++--
> 2 files changed, 14 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index 11323f4..e5d00e6 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -469,6 +469,9 @@ static u32 clocksource_max_adjustment(struct clocksource *cs)
> * @shift: cycle to nanosecond divisor (power of two)
> * @maxadj: maximum adjustment value to mult (~11%)
> * @mask: bitmask for two's complement subtraction of non 64 bit counters
> + *
> + * NOTE: This function includes a saftey margin of 50%, so that bad clock values
Typo.
There's also the same typo in the title of the patch.
Thanks,
Ingo
next prev parent reply other threads:[~2015-03-07 9:22 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-07 2:49 [PATCH 00/12] Increased clocksource validation and cleanups (v3) John Stultz
2015-03-07 2:49 ` [PATCH 01/12] clocksource: Simplify clocks_calc_max_nsecs logic John Stultz
2015-03-07 9:20 ` Ingo Molnar
2015-03-07 2:49 ` [PATCH 02/12] clocksource: Simplify logic around clocksource wrapping saftey margins John Stultz
2015-03-07 9:22 ` Ingo Molnar [this message]
2015-03-07 2:49 ` [PATCH 03/12] clocksource: Remove clocksource_max_deferment() John Stultz
2015-03-07 9:18 ` Ingo Molnar
2015-03-07 2:49 ` [PATCH 04/12] clocksource: Add max_cycles to clocksource structure John Stultz
2015-03-07 9:54 ` Ingo Molnar
2015-03-07 2:49 ` [PATCH 05/12] time: Add debugging checks to warn if we see delays John Stultz
2015-03-07 9:22 ` Paul Bolle
2015-03-07 9:29 ` Ingo Molnar
2015-03-07 2:49 ` [PATCH 06/12] time: Add infrastructure to cap clocksource reads to the max_cycles value John Stultz
2015-03-07 9:32 ` Ingo Molnar
2015-03-07 2:49 ` [PATCH 07/12] time: Try to catch clocksource delta underflows John Stultz
2015-03-07 9:34 ` Ingo Molnar
2015-03-07 2:49 ` [PATCH 08/12] time: Add warnings when overflows or underflows are observed John Stultz
2015-03-07 9:40 ` Ingo Molnar
2015-03-09 16:50 ` John Stultz
2015-03-10 5:05 ` Ingo Molnar
2015-03-07 2:50 ` [PATCH 09/12] clocksource: Improve clocksource watchdog reporting John Stultz
2015-03-07 2:50 ` [PATCH 10/12] clocksource: Mostly kill clocksource_register() John Stultz
2015-03-07 9:45 ` Ingo Molnar
2015-03-07 2:50 ` [PATCH 11/12] sparc: Convert to using clocksource_register_hz() John Stultz
2015-03-07 9:46 ` Ingo Molnar
2015-03-07 2:50 ` [PATCH 12/12] clocksource: Add some debug info about clocksources being registered John Stultz
2015-03-07 9:50 ` Ingo Molnar
2015-03-12 3:16 ` John Stultz
-- strict thread matches above, loose matches on Subject: below --
2015-01-23 0:09 [PATCH 00/12][RFC] Increased clocksource validation and cleanups (v2) John Stultz
2015-01-23 0:09 ` [PATCH 02/12] clocksource: Simplify logic around clocksource wrapping saftey margins John Stultz
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