netdev - Re: [TCP]: min_t/max_t confusion in tcp_select_initial

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Message-ID: <alpine.DEB.2.00.0912232140500.10866@melkinpaasi.cs.helsinki.fi>
Date:	Wed, 23 Dec 2009 21:45:57 +0200 (EET)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	David Miller <davem@...emloft.net>
cc:	roel.kluin@...il.com, Netdev <netdev@...r.kernel.org>
Subject: Re: [TCP]: min_t/max_t confusion in tcp_select_initial_window()?

On Tue, 22 Dec 2009, David Miller wrote:

> From: Roel Kluin <roel.kluin@...il.com>
> Date: Wed, 23 Dec 2009 03:00:24 +0100
> 
> > I could be confused, but in net/ipv4/tcp_output.c:217:
> > 
> >                 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
> >                 space = min_t(u32, space, *window_clamp);
> > ------------------------^^^^^
> > 
> > shouldn't the min_t and max_t be exchanged? i.e.
> > 
> >                 space = min_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
> >                 space = max_t(u32, space, *window_clamp);
> 
> It looks correct to me.
> 
> Globally, the largest window we could ever end up advertising
> is the maximum of the sysctl_tcp_rmem[2] threshold and
> sysctl_rmem_max.
> 
> But for this connection, the window clamp is our upper bound.

I don't understand how window_clamp line could be changed to max_t.
...I guess min in both would seem the most reasonable one?

-- 
 i.
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