Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory

From	Knut Omang <knut.omang@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory
Date	2017-04-25 08:40 +0200
Message-ID	<tA2iL-148-41@gated-at.bofh.it> (permalink)
References	(14 earlier) <twUKK-5ru-7@gated-at.bofh.it> <twVnr-5TD-5@gated-at.bofh.it> <tx1jb-12F-3@gated-at.bofh.it> <tzGLg-45f-9@gated-at.bofh.it> <tzOSu-O4-3@gated-at.bofh.it>
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On Mon, 2017-04-24 at 10:14 -0600, Logan Gunthorpe wrote:
> 
> On 24/04/17 01:36 AM, Knut Omang wrote:
> > My first reflex when reading this thread was to think that this whole domain
> > lends it self excellently to testing via Qemu. Could it be that doing this in 
> > the opposite direction might be a safer approach in the long run even though 
> > (significant) more work up-front?
> 
> That's an interesting idea. We did do some very limited testing on qemu
> with one iteration of our work. However, it's difficult because there is
> no support for any RDMA devices which are a part of our primary use
> case. 

Yes, that's why I used 'significant'. One good thing is that given resources 
it can easily be done in parallel with other development, and will give additional
insight of some form.

> I also imagine it would be quite difficult to develop those models
> given the array of hardware that needs to be supported and the deep
> functional knowledge required to figure out appropriate restrictions.

From my naive perspective it seems it need not even be a full model to get some benefits,
just low level functionality tests with some instances of a
device that offers some MMIO space 'playground'.

Or maybe you can leverage some of the already implemented emulated devices in Qemu?

Knut

> 
> Logan

Thread

Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-12 08:30 +0200
  Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-12 19:20 +0200
    Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-13 00:00 +0200
      Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-13 23:30 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-14 00:40 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Bjorn Helgaas <helgaas@kernel.org> - 2017-04-14 01:30 +0200
          Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-14 06:20 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-14 06:50 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@au1.ibm.com> - 2017-04-14 13:50 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-14 15:00 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-14 13:40 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-14 19:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Bjorn Helgaas <helgaas@kernel.org> - 2017-04-14 21:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-15 00:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-15 19:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-16 00:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-16 05:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-16 06:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-16 18:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-16 18:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-17 01:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Knut Omang <knut.omang@oracle.com> - 2017-04-24 09:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-24 18:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Knut Omang <knut.omang@oracle.com> - 2017-04-25 08:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-25 19:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory "Stephen  Bates" <sbates@raithlin.com> - 2017-04-25 23:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory "Stephen  Bates" <sbates@raithlin.com> - 2017-04-25 23:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-17 00:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-16 00:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-16 07:40 +0200

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