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Re: [PATCH] gettimeofday jumps backwards then forwards

To: Martin Michlmayr <tbm@cyrius.com>, linux-mips@linux-mips.org
Subject: Re: [PATCH] gettimeofday jumps backwards then forwards
From: Dave Johnson <djohnson+linuxmips@sw.starentnetworks.com>
Date: Mon, 16 Jan 2006 11:35:26 -0500
In-reply-to: <20060116160031.GA28383@deprecation.cyrius.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <17118.25343.948383.547250@cortez.sw.starentnetworks.com> <20060116160031.GA28383@deprecation.cyrius.com>
Sender: linux-mips-bounce@linux-mips.org
Martin Michlmayr writes:
> * Dave Johnson <djohnson+linuxmips@sw.starentnetworks.com> [2005-07-20 10:43]:
> > Below are 2 fixes I made to 2.6.12 to do with time jumping around
> > as reported by gettimeofday().  One is SB1250 specific and one appears
> > generic.
> > 
> > The symptom is revealed by running multile copies (1 per cpu) of a
> > simple test program that calls gettimeofday() as fast as possible
> > looking for time to go backwards.
> > 
> > When a jump is detected the program outputs a few samples before and
> > after each jump:
> 
> Does anyone have comments regarding this patch?

In addition to this problem I found significant lost ticks under load
as there is no checking for lost ticks. I'll create a clean patch with
just that fix in a bit.


-- 
Dave Johnson
Starent Networks


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