netdev - Re: [net 1/8] igb: shorten maximum PHC timecounter update interval

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Message-ID: <20181101141239.GF19434@localhost>
Date:   Thu, 1 Nov 2018 15:12:39 +0100
From:   Miroslav Lichvar <mlichvar@...hat.com>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, nhorman@...hat.com,
        sassmann@...hat.com, Jacob Keller <jacob.e.keller@...el.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [net 1/8] igb: shorten maximum PHC timecounter update interval

On Wed, Oct 31, 2018 at 12:42:47PM -0700, Jeff Kirsher wrote:
> From: Miroslav Lichvar <mlichvar@...hat.com>
> 
> The timecounter needs to be updated at least once per ~550 seconds in
> order to avoid a 40-bit SYSTIM timestamp to be misinterpreted as an old
> timestamp.
> 
> Since commit 500462a9d ("timers: Switch to a non-cascading wheel"),
> scheduling of delayed work seems to be less accurate and a requested
> delay of 540 seconds may actually be longer than 550 seconds. Shorten
> the delay to 480 seconds to be sure the timecounter is updated in time.

It looks like this is the v1 of the patch. There was a v2 I sent on
Oct 26, which made the interval even shorter. I can send a separate
patch for that change.

-- 
Miroslav Lichvar