netdev - Re: [PATCH net-next] tcp: Remove some spurious dropped packet profile hits from the passive connection accept path

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Date:	Thu, 20 Nov 2014 13:31:27 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Rick Jones <raj@...dy.usa.hp.com>
CC:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH net-next] tcp: Remove some spurious dropped packet profile
 hits from the passive connection accept path

On 11/20/2014 12:47 PM, Eric Dumazet wrote:
> On Thu, 2014-11-20 at 10:58 -0800, Rick Jones wrote:
>> From: Rick Jones <rick.jones2@...com>
>>
>> When a system is the passive accepter of many connections, for example
>> when the target of a netperf TCP_CC or TCP_CRR test, or as say a web
>> server, the discard of the skb containing the TCP SYN being processed
>> for the LISTEN endpoint should be a consume_skb() rather than a kfree_skb()
>> to avoid cluttering a dropped packet profile.
>>
>> Signed-off-by: Rick Jones <rick.jones2@...com>
>>
>> ---
>
> So what happens if we really drop the packet ?

Do you mean when there is actually data in the SYN?

rick

>
> TCP stack at this point owns the packet, it is possible to mark a bit in
> it to either call consume_skb() or kfree_skb()
>
> I attempted this once but gave up because it was a quite intrusive
> patch...

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