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

From: Mikulas Patocka
Date: Tue Jul 15 2014 - 15:26:48 EST

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
> > 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.

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