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From: David Boreham <david_list@boreham.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Axel Waggershauser <awagger@web.de>
Cc: pgsql-performance@postgresql.org
Subject: Re: Low throughput of binary inserts from windows to linux
Date: Tue, 12 Dec 2006 09:56:02 -0700
Message-ID: <457EDF22.4010303@boreham.org> (raw)
In-Reply-To: <4101.1165941200@sss.pgh.pa.us>
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Tom Lane wrote:

>>In case I was mistaken, this explanation makes perfectly sens to me.
>>But then again it would indicate a 'bug' in libpq, in the sense that
>>it (apparently) sets TCP_NODELAY on linux but not on windows.
>>    
>>
>
>No, it would mean a bug in Windows in that it fails to honor TCP_NODELAY.
>  
>
Last time I did battle with nagle/delayed ack interaction in windows 
(the other end
has to be another stack implementation -- windows to itself I don't 
think has the problem),
it _did_ honor TCP_NODELAY. That was a while ago (1997) but I'd be surprised
if things have changed much since then.

Basically nagle has to be turned off for protocols like this 
(request/response interaction
over TCP) otherwise you'll sometimes end up with stalls waiting for the 
delayed ack
before sending, which in turn results in very low throughput, per 
connection. As I remember
Windows client talking to Solaris server had the problem, but various 
other permutations
of client and server stack implementation did not.

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