netdev - Re: Slow tcp handshakes rate of 2.6.20 and 2.6.19

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Date:	Sat, 28 Apr 2007 06:43:00 +0200
From:	"Robert Iakobashvili" <coroberti@...il.com>
To:	"Quan Sun" <cfk.quan@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Slow tcp handshakes rate of 2.6.20 and 2.6.19

On 4/28/07, Quan Sun <cfk.quan@...il.com> wrote:
> Hi,
>   In these days I met a strange situation, tcp handshake rate is
> slow after 2.6.18.8.
>
>   The case is, server accepts connections, and records number of successful
> tcp handshakes during last 10 seconds. Client tries to connect to server's
> listen port as fast as possible and as many as possible, or in simple words,
> client use connect() to flood the server.  In both cases, there are a log of syn
> re-send.
>
>   Server's performances varied much, depending on which kernel it was
> running. On 2.6.18.8, 10000 successful connections take about 30-40 seconds,
> while on 2.6.20 or 2.6.19, it will cost about more than 5 minutes.

Please, look at this by pressing next_in_thread:
http://marc.info/?l=linux-netdev&m=117664202416020&w=2

What are the
#cat /proc/sys/net/ipv4/tcp_mem values for your kernels?

Do you see tcp memory pressure by
#netstat -s ?

Sincerely,
Robert Iakobashvili,
coroberti %x40 gmail %x2e com
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