linux-kernel - Re: [PATCH net-next] tcp: add SNMP counter for the number of packets pruned from ofo queue

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Date:   Wed, 25 Jul 2018 21:40:04 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] tcp: add SNMP counter for the number of packets
 pruned from ofo queue

On Wed, Jul 25, 2018 at 9:33 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
> On 07/25/2018 06:06 AM, Yafang Shao wrote:
>> LINUX_MIB_OFOPRUNED is used to count how many times ofo queue is pruned,
>> but sometimes we want to know how many packets are pruned from this queue,
>> that could help us to track the dropped packets.
>>
>> As LINUX_MIB_OFOPRUNED is a useful event for us, so I introduce a new
>> SNMP counter LINUX_MIB_OFOPRUNEDROP, which could be showed in netstat as
>> OfoPruneDrop.
>
>
> Okay, but why tracking number of skbs that are removed ?
>

Because we want to know why packets were dropped.
If that could be show in netstat, we could easily find that it is
dropped due to ofo prune.


> Skb can contain many segments (because of GRO and TCP coalescing)
>
> So your claim of tracking dropped packets is ill defined.
>
> Also I prefer having net tree being merged into net-next, since your patch would
> add a merge conflict.
>
>