netdev - Re: [net-next PATCH v4 2/3] net: TCP thin linear timeouts

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Message-ID: <4B7CFDE4.4010003@simula.no>
Date:	Thu, 18 Feb 2010 09:44:20 +0100
From:	Andreas Petlund <apetlund@...ula.no>
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
CC:	Netdev <netdev@...r.kernel.org>, eric.dumazet@...il.com,
	hannemann@...s.rwth-aachen.de, LKML <linux-kernel@...r.kernel.org>,
	shemminger@...tta.com, william.allen.simpson@...il.com,
	damian@....rwth-aachen.de, ebiederm@...ssion.com,
	David Miller <davem@...emloft.net>
Subject: Re: [net-next PATCH v4 2/3] net: TCP thin linear timeouts

On 02/18/2010 09:41 AM, Ilpo Järvinen wrote:
> On Wed, 17 Feb 2010, David Miller wrote:
> 
>> From: Andreas Petlund <apetlund@...ula.no>
>> Date: Tue, 16 Feb 2010 15:40:41 +0100
>>
>>> @@ -341,6 +342,8 @@ struct tcp_sock {
>>>  	u16	advmss;		/* Advertised MSS			*/
>>>  	u8	frto_counter;	/* Number of new acks after RTO */
>>>  	u8	nonagle;	/* Disable Nagle algorithm?             */
>>> +	u8      thin_lto    : 1,/* Use linear timeouts for thin streams */
>>> +		thin_undef  : 7;
>>>  
>>
>> There is now a gap of 3 unused bytes here in this critical
>> core TCP socket data structure.
>>
>> Please either find a way to avoid this hole, or document
>> it with a comment.
> 
> There would be multiple bits free for use in both frto_counter and nonagle 
> byte.
> 

I was playing aroud with this setup:

=========
u8	nonagle     : 4,/* Disable Nagle algorithm?             */
	thin_lto    : 1,/* Use linear timeouts for thin streams */
	thin_dupack : 1,/* Fast retransmit on first dupack      */
	thin_undef  : 2;
=========

Do you think that would do the trick?

Regards,
Andreas
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