RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V

From	KY Srinivasan <kys@microsoft.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V
Date	2015-09-17 23:20 +0200
Message-ID	<q9OKZ-7kB-11@gated-at.bofh.it> (permalink)
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> -----Original Message-----
> From: David Miller [mailto:davem@davemloft.net]
> Sent: Thursday, September 17, 2015 1:11 PM
> To: KY Srinivasan <kys@microsoft.com>
> Cc: David.Laight@ACULAB.COM; alexander.duyck@gmail.com; Haiyang Zhang
> <haiyangz@microsoft.com>; vkuznets@redhat.com; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org; jasowang@redhat.com
> Subject: Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V
> 
> From: KY Srinivasan <kys@microsoft.com>
> Date: Thu, 17 Sep 2015 19:52:01 +0000
> 
> >
> >
> >> -----Original Message-----
> >> Have a pre-cooked ring of buffers for these descriptors that you can
> >> point the chip at.  No per-packet allocation is necessary at all.
> >
> > Even if I had a ring of buffers, I would still need to manage the life cycle
> > of these buffers - selecting an unused one on the transmit path and marking
> > it used (atomically).
> 
> Have one per TX ring entry, then the lifetime matches the lifetime of the
> TX entry itself and therefore you need do nothing.

Yes, I understand. Unfortunately, the ring buffer used on Hyper-V to send the packets to the host is not
managed as a traditional TX ring entries - it is not fixed size and a given packet can wrap around and lastly, I think
the management of space on the ring buffer is not tied to the act of completing the send operation. That is why
we have an explicit "send complete" message.

I am working on moving the model to more closely match the hardware model but it will take some time.
For now, I will implement a very light weight mechanism for managing the additional memory needed.

Regards,

K. Y
> 
> That's the whole idea.

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[PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V Vitaly Kuznetsov <vkuznets@redhat.com> - 2015-09-16 18:00 +0200
  RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V Haiyang Zhang <haiyangz@microsoft.com> - 2015-09-16 18:10 +0200
    RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V David Laight <David.Laight@ACULAB.COM> - 2015-09-16 18:30 +0200
      Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V Alexander Duyck <alexander.duyck@gmail.com> - 2015-09-16 19:30 +0200
      Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V David Miller <davem@davemloft.net> - 2015-09-16 20:00 +0200
        Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V Vitaly Kuznetsov <vkuznets@redhat.com> - 2015-09-17 11:10 +0200
      RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V KY Srinivasan <kys@microsoft.com> - 2015-09-16 20:00 +0200
        Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V Alexander Duyck <alexander.duyck@gmail.com> - 2015-09-16 23:40 +0200
          RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V KY Srinivasan <kys@microsoft.com> - 2015-09-17 01:40 +0200
            Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V Alexander Duyck <alexander.duyck@gmail.com> - 2015-09-17 01:50 +0200
              RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V KY Srinivasan <kys@microsoft.com> - 2015-09-17 02:00 +0200
            RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V David Laight <David.Laight@ACULAB.COM> - 2015-09-17 10:40 +0200
              RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V KY Srinivasan <kys@microsoft.com> - 2015-09-17 17:20 +0200
                Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V David Miller <davem@davemloft.net> - 2015-09-17 21:00 +0200
                RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V KY Srinivasan <kys@microsoft.com> - 2015-09-17 22:00 +0200
                Re: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V David Miller <davem@davemloft.net> - 2015-09-17 22:20 +0200
                RE: [PATCH net-next RFC] net: increase LL_MAX_HEADER for Hyper-V KY Srinivasan <kys@microsoft.com> - 2015-09-17 23:20 +0200

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