Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <CALOAHbASvcEdudqpit-c=RRZ8xVD+G+0jU-ynp9PsH4_mU7xjw@mail.gmail.com>
References: <1532524010-11855-1-git-send-email-laoar.shao@gmail.com>
 <047bc12f-9eb5-e512-10c5-6334c494c77e@gmail.com> <CALOAHbCC=oWgzcA=VhkXq0rVLBa5_TvtbKtTqESGrgxvYTtH6w@mail.gmail.com>
 <096a8a2f-ea32-2107-b2af-c246450cc3b9@gmail.com> <CALOAHbASvcEdudqpit-c=RRZ8xVD+G+0jU-ynp9PsH4_mU7xjw@mail.gmail.com>
From:   Yafang Shao <laoar.shao@gmail.com>
Date:   Thu, 26 Jul 2018 09:42:50 +0800
Message-ID: <CALOAHbAHgEF_=w_hbd_03NOH3h9m-4W=UJ0HCYGK0BtEyq=5Tw@mail.gmail.com>
Subject: Re: [PATCH net-next] tcp: add SNMP counter for the number of packets
 pruned from ofo queue
To:     Eric Dumazet <eric.dumazet@gmail.com>
Cc:     David Miller <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jul 25, 2018 at 9:59 PM, Yafang Shao <laoar.shao@gmail.com> wrote:
> On Wed, Jul 25, 2018 at 9:55 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>
>>
>> On 07/25/2018 06:40 AM, Yafang Shao wrote:
>>
>>>
>>> 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.
>>
>>
>> We have a counter already for these events : LINUX_MIB_OFOPRUNED
>>
>> You want to add another counter tracking number of _skbs_,
>> which has no precise value for user,
>> given each skb can contain a variable number of _packets_.
>>
>
> Got it.
>
> But with LINUX_MIB_OFOPRUNED, we only know  tcp_prune_ofo_queue is
> called, but have no idea how many skbs are dropped.
>


Hi Eric,

LINUX_MIB_TCPOFOQUEUE, LINUX_MIB_TCPOFODROP and LINUX_MIB_TCPOFOMERGE
are all for the number of SKBs, but only  LINUX_MIB_OFOPRUNED is for
the event, that could lead misunderstading.
So I think introducing a counter for the number of SKB pruned could be
better, that could help us to track the whole behavior of ofo queue.
That is why I submit this patch.


Thanks
Yafang