linux-kernel - Loopback and Nagle's algorithm

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Message-Id: <1302575869.13492.1440076201@webmail.messagingengine.com>
Date:	Mon, 11 Apr 2011 22:37:49 -0400
From:	"Adam McLaurin" <lkml@...tas.net>
To:	linux-kernel@...r.kernel.org
Subject: Loopback and Nagle's algorithm

I understand that disabling Nagle's algorithm via TCP_NODELAY will
generally degrade throughput. However, in my scenario (150 byte
messages, sending as fast as possible), the actual throughput penalty
over the network is marginal (maybe 10% at most).

However, when I disable Nagle's algorithm when connecting over loopback,
the performance hit is *huge* - 10x reduction in throughput.

The question is, why is disabling Nagle's algorithm on loopback so much
worse w.r.t. throughput? Is there anything I can do to reduce the
incurred throughput penalty?

Thanks,
Adam
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