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: <1391871986.10160.105.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Sat, 08 Feb 2014 07:06:26 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Thomas Glanzmann <thomas@...nzmann.de>
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]

On Sat, 2014-02-08 at 16:00 +0100, Thomas Glanzmann wrote:
> Hello Eric,
> 
> > Idea would be to set this flag when calling sendmsg() of the 48 bytes
> > of the header, and not set it on the sendmsg() of the 512 bytes of the
> > payload.
> 
> I see.
> 
> > iscsi_sw_tcp_xmit_segment() already adds MSG_MORE, but
> > it would be nice to add a new _initial_ flags parameter to
> > iscsi_sw_tcp_xmit_segment()
> 
> This is for the iscsi initiator implementation. I'm interested in iSCSI
> target code, but I already found it and experiemented a little bit, but
> I need to dig deeper if I want to prepare a patch.

Fantastic !

Let me know if you want some help.

Note : We did some patches in the MSG_MORE logic for sendpage(), but in
your case I do not think its related

(git grep -n MSG_SENDPAGE_NOTLAST ) if you are curious


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