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Re: [net-next][PATCH v2 11/13] RDS: IB: add Fastreg MR (FRMR) detection support

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On 2/28/16 1:08 AM, Christoph Hellwig wrote:
> On Sat, Feb 27, 2016 at 06:19:48PM -0800, Santosh Shilimkar wrote:
>> Discovere Fast Memmory Registration support using IB device
>> IB_DEVICE_MEM_MGT_EXTENSIONS. Certain HCA might support just FRMR
>> or FMR or both FMR and FRWR. In case both mr type are supported,
>> default FMR is used.
>>
>> Default MR is still kept as FMR against what everyone else
>> is following. Default will be changed to FRMR once the
>> RDS performance with FRMR is comparable with FMR. The
>> work is in progress for the same.
>>
>> Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
>> ---
>> v2: Dropped the module parameter as suggested by David Miller
>
> This means we only use the safer method if the HCA doesn't support
> the other one.  All other RDMA ULP that support both methods have
> a module_param so the veto from Dave is a bit unfortunate.  Anyway,
> let's get the code in for now and figure out what to use later.
>
Indeed. It wasn't really deal breaker for RDS so I agreed to drop it.

> Just curious:  where / how do you see worse peformance using FRs?
>
I wouldn't call it worse but its not comparable. Use case
is multi-threaded RDS RDMA perf test(s). Hopefully the follow
up series which am working on should minimise the gap. I am
leaving the details for later, but one of the main issue I
saw was contention on driver post_send() lock from send, MR reg
and MR invalidation.

Regards,
Santosh

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[net-next][PATCH v2 00/13] RDS: Major clean-up with couple of new features for 4.6 Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 12/13] RDS: IB: allocate extra space on queues for FRMR support Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 09/13] RDS: IB: handle the RDMA CM time wait event Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 04/13] RDS: IB: Remove the RDS_IB_SEND_OP dependency Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 10/13] RDS: IB: add mr reused stats Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 11/13] RDS: IB: add Fastreg MR (FRMR) detection support Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
    Re: [net-next][PATCH v2 11/13] RDS: IB: add Fastreg MR (FRMR)  detection support Christoph Hellwig <hch@infradead.org> - 2016-02-28 10:10 +0100
      Re: [net-next][PATCH v2 11/13] RDS: IB: add Fastreg MR (FRMR)  detection support "santosh.shilimkar@oracle.com" <santosh.shilimkar@oracle.com> - 2016-02-28 11:30 +0100
  [net-next][PATCH v2 02/13] RDS: Add support for SO_TIMESTAMP for incoming messages Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 05/13] RDS: IB: Re-organise ibmr code Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 03/13] MAINTAINERS: update RDS entry Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 08/13] RDS: IB: add connection info to ibmr Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  [net-next][PATCH v2 13/13] RDS: IB: Support Fastreg MR (FRMR) memory registration mode Santosh Shilimkar <santosh.shilimkar@oracle.com> - 2016-02-28 03:30 +0100
  Re: [net-next][PATCH v2 00/13] RDS: Major clean-up with couple of  new features for 4.6 David Miller <davem@davemloft.net> - 2016-03-01 23:40 +0100
    Re: [net-next][PATCH v2 00/13] RDS: Major clean-up with couple of new  features for 4.6 santosh shilimkar <santosh.shilimkar@oracle.com> - 2016-03-02 00:10 +0100

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