netdev - Re: [PATCH net-next] tcp: use TCP_DEFAULT_INIT_RCVWND in tcp_fixup

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Message-Id: <20111020.161356.2120784879469409197.davem@davemloft.net>
Date:	Thu, 20 Oct 2011 16:13:56 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: use TCP_DEFAULT_INIT_RCVWND in
 tcp_fixup_rcvbuf()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 20 Oct 2011 22:02:34 +0200

> Le jeudi 20 octobre 2011 à 15:50 -0400, David Miller a écrit :
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Thu, 20 Oct 2011 21:16:26 +0200
>> 
>> > Since commit 356f039822b (TCP: increase default initial receive
>> > window.), we allow sender to send 10 (TCP_DEFAULT_INIT_RCVWND) segments.
>> > 
>> > Change tcp_fixup_rcvbuf() to reflect this change, even if no real change 
>> > is expected, since sysctl_tcp_rmem[1] = 87380 and this value
>> > is bigger than tcp_fixup_rcvbuf() computed rcvmem (~23720)
>> > 
>> > Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
>>  ...
>> > +	unsigned int mss = min_t(unsigned int, tp->advmss, 1460);
>> 
>> I don't understand where this calculation comes from, and even if it
>> should be obvious it isn't to me and deserves a mention in the commit
>> message at a minimum.
> 
> This is the calculation done in commit 356f039822b as well.
> 
> The window is 10*MSS, but no more than 14600
> 
> On loopback, this matters, because we could end with rcvmem=219680

Thanks, please help weak brains like mine by adding this to the commit message.
:-)
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