From: Andi Kleen <ak@muc.de>
To: Tim Bird <tim.bird@am.sony.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Is there a problem in timeval_to_jiffies?
Date: Thu, 30 Sep 2004 00:03:03 +0200 [thread overview]
Message-ID: <m3d604u414.fsf@averell.firstfloor.org> (raw)
In-Reply-To: <2JTS7-5Ri-3@gated-at.bofh.it> (Tim Bird's message of "Wed, 29 Sep 2004 23:10:07 +0200")
Tim Bird <tim.bird@am.sony.com> writes:
> Henry Margies wrote:
>> Right? But for arm, with a jiffie size of 10000000, it is much
>> more easier. And that is why I don't understand why an one second
>> interval is converted to 101 jiffies (on arm).
> ...
>> I agree. But then, why adding one jiffie to every interval? If
>> there is no latency, the timer should appear right at the
>> beginning of a jiffie. For x86 you are right, because 10 jiffies
>> are less then 10ms. But for arm, 1 jiffie is precisely 10ms.
>
> How does the computer "know" that the timer is at the beginning
> of the jiffy? By definition, Linux (without HRT support) has
do_gettimeofday() or better the posix monotonic clock normally have
much better resolution than a jiffie (on x86 typically the resolution
of the CPU clock) xtime is the T-O-D of the last jiffie
However calling do_gettimeofday and doing the calculation may
be too expensive.
-Andi
next parent reply other threads:[~2004-09-29 22:03 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <2CxDn-2ib-51@gated-at.bofh.it>
[not found] ` <2DDGs-7Om-31@gated-at.bofh.it>
[not found] ` <2EVhQ-6Qe-5@gated-at.bofh.it>
[not found] ` <2F1e7-2r9-21@gated-at.bofh.it>
[not found] ` <2Fb3o-1cT-27@gated-at.bofh.it>
[not found] ` <2Fb3o-1cT-25@gated-at.bofh.it>
[not found] ` <2FnQM-1wt-1@gated-at.bofh.it>
[not found] ` <2JTS7-5Ri-3@gated-at.bofh.it>
2004-09-29 22:03 ` Andi Kleen [this message]
2004-09-09 13:48 Is there a problem in timeval_to_jiffies? Henry Margies
2004-09-12 14:33 ` Henry Margies
2004-09-16 3:30 ` Randy.Dunlap
2004-09-16 9:54 ` George Anzinger
2004-09-16 15:38 ` Henry Margies
2004-09-16 18:10 ` Henry Margies
[not found] ` <20040916200203.6259e113.henry.margies@gmx.de>
2004-09-16 20:19 ` George Anzinger
2004-09-17 9:55 ` Henry Margies
2004-09-29 20:56 ` Tim Bird
2004-09-29 21:24 ` Jon Masters
2004-10-01 11:42 ` Henry Margies
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