netdev - Re: [PATCH net-next 2/2] sunvnet: Re-check for a VIO_DESC_READY data descriptor after short udelay()

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Message-ID: <54074C18.2090207@oracle.com>
Date:	Wed, 03 Sep 2014 13:12:56 -0400
From:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:	David Miller <davem@...emloft.net>
CC:	raghuram.kothakota@...cle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] sunvnet: Re-check for a VIO_DESC_READY data
 descriptor after short udelay()

On 09/02/2014 04:59 PM, David Miller wrote:
> From: Sowmini Varadhan <sowmini.varadhan@...cle.com>
> Date: Tue, 02 Sep 2014 06:27:54 -0400
>
>> when there are no more packets coming, the extra 12 microsecond
>> delay is not that big of a deal anyway.
>
> How much other work could the cpu do in those 12 microseconds?
>
> That's almost 3000 cpu cycles on a T4.
>
> I understand your argument, and the fact that there are some existing
> pieces of code doing this already, so I'll think about it some more.
>
> Thanks.
>

Maybe we should just leave out patch 2/2 for now, and only retain 1/2.
I was always somewhat ambivalent about the fudge-factor anyway,
and there are plenty of other things we can do to get better
perf- we could revisit this one afterward, if it still makes
a difference.

--Sowmini

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