linux-kernel - Re: REGRESSION f54b311142a92ea2e42598e347b84e1655caf8e3 tcp auto corking slows down iSCSI file system creation by factor of 70 [WAS: 4 TB VMFS creation takes 15 minutes vs 26 seconds]

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Message-ID: <20140208133847.GB20512@glanzmann.de>
Date:	Sat, 8 Feb 2014 14:38:47 +0100
From:	Thomas Glanzmann <thomas@...nzmann.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	John Ogness <john.ogness@...utronix.de>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	target-devel <target-devel@...r.kernel.org>,
	Linux Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: REGRESSION f54b311142a92ea2e42598e347b84e1655caf8e3 tcp auto
 corking slows down iSCSI file system creation by factor of 70 [WAS: 4 TB
 VMFS creation takes 15 minutes vs 26 seconds]

Hello Eric,

> Also make sure you have commit a181ceb501b31b4bf8812a5c84c716cc31d82c2d
> ("tcp: autocork should not hold first packet in write queue")
> in your tree.

confirmed:

(node-62) [~/work/linux-2.6] git show a181ceb501b31b4bf8812a5c84c716cc31d82c2d | head
commit a181ceb501b31b4bf8812a5c84c716cc31d82c2d
Author: Eric Dumazet <edumazet@...gle.com>
Date:   Tue Dec 17 09:58:30 2013 -0800

    tcp: autocork should not hold first packet in write queue

    Willem noticed a TCP_RR regression caused by TCP autocorking
    on a Mellanox test bed. MLX4_EN_TX_COAL_TIME is 16 us, which can be
    right above RTT between hosts.

Cheers,
        Thomas
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