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Date: Thu, 16 Oct 2014 15:30:20 +0200
From: Hans Petter Selasky <hps@selasky.org>
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To: Mateusz Guzik <mjguzik@gmail.com>
Subject: Re: svn commit: r273135 - in head/sys: contrib/rdma/krping
 dev/cxgbe/iw_cxgbe
 ofed/drivers/infiniband/core ofed/drivers/infiniband/hw/mlx4
 ofed/drivers/infiniband/hw/mthca ofed/drivers/infiniband/ulp/i...
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 <20141016123908.GA10350@dft-labs.eu>
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On 10/16/14 14:39, Mateusz Guzik wrote:
> On Wed, Oct 15, 2014 at 01:40:30PM +0000, Hans Petter Selasky wrote:
>> Author: hselasky
>> Date: Wed Oct 15 13:40:29 2014
>> New Revision: 273135
>> URL: https://svnweb.freebsd.org/changeset/base/273135
>>
>> Log:
>>    Update the OFED Linux compatibility layer and
>>    Mellanox hardware driver(s):
>>
>>    - Properly name an inclusion guard
>>    - Fix compile warnings regarding unsigned enums
>>    - Add two new sysctl nodes
>>    - Remove all empty linux header files
>>    - Make an error printout more verbose
>>    - Use "mod_delayed_work()" instead of
>>      cancelling and starting a timeout.
>>    - Implement more Linux scatterlist
>>      functions.
>>
>
> Do you have ofed benchmarks by any chance?
>
> In linux they use atomic_read which just reads the var and so on, while
> our compat layer issues full memory barrier in such case (i.e. does it
> in an expensive way providing guarantees not needed by the code).
>
> I would suggest investigating re-implementation of the layer with
> relaxed functions and checking if it improves stuff.
>
> Just my $0,03.
>

Hi Mateusz,

We have not specifically investigated all parts of the OFED layer, and 
your comments are valid. There is indeed room for improvement. Do you 
have a patch suggestion?

--HPS