linux-kernel - Re: [PATCH] aoe: Use 64-bit timestamp in frame

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Date:	Tue, 12 May 2015 21:26:35 -0400
From:	Ed Cashin <ed.cashin@....org>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Tina Ruchandani <ruchandani.tina@...il.com>,
	y2038@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] aoe: Use 64-bit timestamp in frame

On 05/12/2015 05:44 AM, Arnd Bergmann wrote:
> On Monday 11 May 2015 21:00:25 Ed Cashin wrote:
...
> In that case, there is still information about the timing embedded in
> the AoE tag.  The send time in jiffies is a rough-grained record of the
> send time, and it's extracted from the tag.  For these "unexpected"
> responses, this timing information can improve performance significantly
> without introducing extra overhead or risk.
> That path is not changed at all by this patch, right? It also looks
> like the jiffies information from there is only used to print an
> error message.
>

That's right, thanks, the tag still has the old jiffies embedded
in it.

The information, though, is used to update the round-trip-time
average and the running estimate of the RTT variance.  For the
unexpected responses that information can help the driver to
maintain high performance when there are inconsistencies in the
network performance.  (calc_rttavg)

-- 
   Ed
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