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From: Tom Lane <tgl@sss.pgh.pa.us>
To: 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 11:33:20 -0500
Message-ID: <4101.1165941200@sss.pgh.pa.us> (raw)
In-Reply-To: <5e66c6e90612120218p435bc0a6i80f1158fae970b9a@mail.gmail.com>
References: <5e66c6e90612080417r23ecaea4p210905f868c26c7f@mail.gmail.com>
	<5e66c6e90612081724m57293ffdy21d6b45697e69bd4@mail.gmail.com>
	<3317.1165636358@sss.pgh.pa.us>
	<5e66c6e90612110658r3c0918f6v4fd3682363db5c15@mail.gmail.com>
	<12645.1165852740@sss.pgh.pa.us>
	<5e66c6e90612111444y78729a71m4ec9852ae9bc8567@mail.gmail.com>
	<21549.1165886726@sss.pgh.pa.us>
	<5e66c6e90612120218p435bc0a6i80f1158fae970b9a@mail.gmail.com>

"Axel Waggershauser" <awagger@web.de> writes:
> On 12/12/06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I think this almost certainly indicates a Nagle/delayed-ACK
>> interaction.  I googled and found a nice description of the issue:
>> http://www.stuartcheshire.org/papers/NagleDelayedAck/

> 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.
Again, given that you only see the behavior at one specific message
length, I suspect this is a corner case rather than a generic "it
doesn't work" issue.

We're pretty much guessing though.  Have you tried tracing the traffic
with a packet sniffer to see what's really happening at different
message sizes?

			regards, tom lane



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