Re: [PATCH for-3.11 7/7] IB/iser: Introduce fast memory registration model (FRWR)

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 07/22/13 15:11, Sagi Grimberg wrote:
> So just to clarify the flow:
> . at connection establishment allocate pool of fastreg descriptors
> . upon each IOP take a fastreg descriptor from the pool
>      . if it is not invalidated - invalidate it.
>      . register using FRWR.
> . when cleanup_task is called - just return the fastreg descriptor to
> the pool.
> . at connection teardown free all resources.
> Still to come:
> . upon each IOP response, check if the target used remote invalidate -
> if so mark relevant fastreg as valid.

Hello Sagi and Or,

Thanks for the clarifications. I have one more question though. My 
interpretation of section "10.6 Memory Management" in the IB 
specification is that memory registration maps a memory region that 
either has contiguous virtual addresses or contiguous physical 
addresses. However, there is no such requirement for an sg-list. As an 
example, for direct I/O to a block device with a sector size of 512 
bytes it is only required that I/O occurs in multiples of 512 bytes and 
from memory aligned on 512-byte boundaries. So the use of direct I/O can 
result in an sg-list where the second and subsequent sg-list elements 
have a non-zero offset. Do you agree with this ? Are such sg-lists 
mapped correctly by the FRWR code ?

Bart.

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