Re: [SPDK] SPDK NVMe CMB WDS/RDS Support: Thanks and next steps!

[Harris, James R <james.r.harris at intel.com>]

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On 2/15/18, 2:02 PM, "Stephen  Bates" <sbates(a)raithlin.com> wrote:

    Jim
    
    > We also need a better CMB allocation scheme.  
    
    Ha! I knew there was a feature I was forgetting. This is it. Yes for sure, thanks for reminding me. I have added it to my list so I don't forget next time. 
    
  Do we have anything like this in SPDK already or does anyone have any pointers to a licence compatible open-source allocator that might suit our needs?


There’s really nothing like this today in SPDK.  I believe DPDK provides a way to use their allocators with “user-provided” memory – i.e. not from the hugepages allocated in host memory by DPDK.  But I haven’t looked at exactly how that works.

I guess I’m not 100% sold that we need a full-blown allocator.  Maybe what we have currently is enough – the user can allocate the memory but it’s up to the user how it is managed.  Meaning that the free_cmb_io_buffer routine effectively goes away.  And just be explicit in the API – i.e. here’s the call you make to get the CMB buffer and its size – what you choose to do with it is your business.  We could always provide some kind of allocator later – but that can be done outside of the SPDK NVMe CMB logic itself.

I’m curious – how much CMB does one of your NoLoad card have?

-Jim