netdev - Re: [PATCH v3 3/3] tcp: early retransmit: delayed fast retransmit

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Date:	Wed, 2 May 2012 14:17:20 -0700
From:	Yuchung Cheng <ycheng@...gle.com>
To:	Neal Cardwell <ncardwell@...gle.com>
Cc:	davem@...emloft.net, ilpo.jarvinen@...sinki.fi,
	nanditad@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH v3 3/3] tcp: early retransmit: delayed fast retransmit

On Wed, May 2, 2012 at 12:34 PM, Neal Cardwell <ncardwell@...gle.com> wrote:
> On Wed, May 2, 2012 at 2:46 PM, Yuchung Cheng <ycheng@...gle.com> wrote:
>> Implementing the advanced early retransmit (sysctl_tcp_early_retrans==2).
>> Delays the fast retransmit by an interval of RTT/4. We borrow the
>> RTO timer to implement the delay. If we receive another ACK or send
>> a new packet, the timer is cancelled and restored to original RTO
>> value offset by time elapsed.  When the delayed-ER timer fires,
>> we enter fast recovery and perform fast retransmit.
>>
>> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
>> ---
>> ChangeLog in v2:
>>  - Set sysctl_tcp_early_retrans default to 2
>> ChangeLog in v3:
>>  - use separate u8 for early retrans stats in tcp_sock
>>  - disable ER if detects any reordering
>
> After reading patch 3 of the series, I see that patch 3 incorporates
> most of those suggestions from Monday. I think it would be quite a bit
> cleaner to just have patch 2 of the series put the
> tcp_disable_early_retrans() call and tcp_sock fields in the ultimately
> desired place, rather than having patch 2 put them somewhere and patch
> 3 move them, but maybe that's just me.
>
> When all the patches in the series are applied, the one issue I still
> see is that frto_counter is in a new place, a bit further away from
> frto_highmark than it used to be before the patch series. I think it
> would be good  to keep frto_counter in its original location, back up
> nearer to frto_highmark.
Sorry for keep mis-placing the changes in different patch parts. Will fix asap.

>
> neal
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