linux-kernel - Re: ANNOUNCE: SCSI XCOPY support for the kernel and device mapper

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Message-ID: <alpine.LRH.2.02.1407151523120.14632@file01.intranet.prod.int.rdu2.redhat.com>
Date:	Tue, 15 Jul 2014 15:26:10 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
cc:	"Alasdair G. Kergon" <agk@...hat.com>,
	Mike Snitzer <msnitzer@...hat.com>,
	Jonathan Brassow <jbrassow@...hat.com>,
	Edward Thornber <thornber@...hat.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Jens Axboe <axboe@...nel.dk>, dm-devel@...hat.com,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: ANNOUNCE: SCSI XCOPY support for the kernel and device mapper



On Tue, 15 Jul 2014, Christoph Hellwig wrote:

> On Tue, Jul 15, 2014 at 02:33:13PM -0400, Mikulas Patocka wrote:
> > Hi
> > 
> > I annouce that I released the first version of a patch set that makes it 
> > possible to use SCSI XCOPY offload for the block layer and device mapper.
> > 
> > The patchset is at 
> > http://people.redhat.com/~mpatocka/patches/kernel/xcopy/series.html It 
> > requires kernel version at least 3.16-rc4. It was tested on target-core 
> > iSCSI implementation.
> 
> Can you send the series to the mainling list(s)?  That makes it a lot
> easier to do a quick review.

I'll post them to the lists.

> > The dm-kcopyd subsystem is modified to use the XCOPY command, so device 
> > mapper targets that use it (mirror, snapshot, thin, cache) take advantage 
> > of copy offload automatically.
> 
> That sounds good, do you have any benchmarking data that shows the
> advantage of using XCOPY?

dm-mirror resynchronization is 4 times faster with XCOPY offload, but it 
is just a benchmark on a network with iSCSI between two slow machines.

I hope that we get some benchmarks on a real hardware.

Mikulas
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