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Date: Wed, 15 Jun 2005 08:01:10 -0700
From: Nishanth Aravamudan <nacc@us.ibm.com>
To: Ulrich Windl <ulrich.windl@rz.uni-regensburg.de>
Cc: lkml <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH 0/4] new timeofday-based soft-timer subsystem
Message-ID: <20050615150110.GC19520@us.ibm.com>
References: <20050614034655.GA4180@us.ibm.com> <42AFE71B.1181.2422D280@rkdvmks1.ngate.uni-regensburg.de>
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On 15.06.2005 [08:30:20 +0200], Ulrich Windl wrote:
> On 14 Jun 2005 at 11:11, Nishanth Aravamudan wrote:
> 
> [...]
> > Would it be beneficial to encapsulate the timer_list structure? That way
> > if the units change underneath and we eventually move to timer_fsecs
> > (for femtoseconds), we don't need to change all the callers of
> > set_timer_nsecs() again?
> [...]
> 
> I don't think that we'll see a global clock with reliable femtosecond
> resolution (not to talk about accuracy) in the foreseeable computer
> generations. Even plain gigahertz RAM is quite some time away. So how
> would you distribute such high resolution time across CPUs? As long as
> a syscall takes significantly longer than 1ns, or has a jitter of more
> than 1ns, a higher resolution clock would be just a source of
> additional noise bits.

Thank you for your feedback, Ulrich. You are probably right that such a
hardware timesource probably is not going to be common any time soon. My
thoughts for encapsulation were just a possibility, and certainly not a
requirement for my patch.

I did not consider the problems of distributing that value, either. So,
I guess, I can leave encapsulation out of the current efforts :)

Thanks,
Nish