netdev - Re: [PATCH] sctp: Do not account for sizeof(struct sk

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Date:	Tue, 20 Dec 2011 13:00:48 +0800
From:	Wei Yongjun <weiyj.lk@...il.com>
To:	tgraf@...radead.org
Cc:	vladislav.yasevich@...com, linux-sctp@...r.kernel.org,
	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] sctp: Do not account for sizeof(struct sk_buff) in
 estimated rwnd

Hi Thomas,

> On Mon, Dec 19, 2011 at 03:11:40PM +0100, Thomas Graf wrote:
>> Trying to reproduce this I found that with the sk_buff overhead removed,
>> the performance would improve significantly unless socket buffer limits
>> are increased.
> I believe this is likely to be misunderstood. What I meant is that by
> removing the sk_buff overhead and while using default socket buffer limits
> the performance increases as shown below. If socket buffers are enlarged
> performance differences fade until there is no longer any difference.
>
> Sorry for poor wording.
>
>> The following numbers have been gathered using a patched iperf
>> supporting SCTP over a live 1 Gbit ethernet network. The -l option
>> was used to limit DATA chunk sizes. The numbers listed are based on
>> the average of 3 test runs each. Default values have been used for
>> sk_(r|w)mem.
>>
>> Chunk
>> Size    Unpatched     No Overhead
>> -------------------------------------
>>    4    15.2 Kbit [!]   12.2 Mbit [!]
>>    8    35.8 Kbit [!]   26.0 Mbit [!]
>>   16    95.5 Kbit [!]   54.4 Mbit [!]
>>   32   106.7 Mbit      102.3 Mbit
>>   64   189.2 Mbit      188.3 Mbit
>>  128   331.2 Mbit      334.8 Mbit
>>  256   537.7 Mbit      536.0 Mbit
>>  512   766.9 Mbit      766.6 Mbit
>> 1024   810.1 Mbit      808.6 Mbit

I saw you discussed this with Vlad in old mail:
    http://www.spinics.net/lists/linux-sctp/msg01365.html

You said you will update patch to include a per packet overhead,
but it does not include in this patch, what's wrong with in?



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