netdev - Re: [PATCH -next] net: tcp: add mib counters to track zero window transitions

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Message-ID: <20140219191831.GA7119@breakpoint.cc>
Date:	Wed, 19 Feb 2014 20:18:31 +0100
From:	Florian Westphal <fw@...len.de>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH -next] net: tcp: add mib counters to track zero window
 transitions

Hannes Frederic Sowa <hannes@...essinduktion.org> wrote:
> On Wed, Feb 19, 2014 at 10:49:47AM -0800, Eric Dumazet wrote:
> > On Wed, 2014-02-19 at 13:17 -0500, David Miller wrote:
> > > From: Florian Westphal <fw@...len.de>
> > > Date: Mon, 17 Feb 2014 22:57:48 +0100
> > > 
> > > > Three counters are added:
> > > > - one to track when we went from non-zero to zero window
> > > > - one to track the reverse
> > > > - one counter incremented when we want to announce zero window.
> > > > 
> > > > The latter is added because it can show cases where we want to close the
> > > > window but can't because we would shrink window.
> > > > 
> > > > Suggested-by: Eric Dumazet <edumazet@...gle.com>
> > > > Signed-off-by: Florian Westphal <fw@...len.de>
> > > > ---
> > > >  Eric, is this what you had in mind?
> > > > 
> > > >  I re-ran my 'slow-sender-with-reader-that-does-not-drain-socket'
> > > >  scenario and, as expected, only TCPWANTZEROWINDOW increases.
> > > 
> > > Eric, ping?
> > 
> > Thanks, I missed this patch. Let me think about it, thanks !
> 
> We need NET_INC_STATS instead of NET_INC_STATS_BH, no?

sure, I can send v2 but I'll wait for (n)ack from Eric first
before considering it.

tcp_transmit_skb (caller of tcp_select_window) also uses _BH
which is why it ended up in tcp_select_window.
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