Re: [PATCH 9/9] IB/srp: Add fast registration support

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

On 05/07/14 19:19, Sagi Grimberg wrote:
> On 5/7/2014 5:59 PM, Bart Van Assche wrote:
>> On 05/07/14 13:34, Sagi Grimberg wrote:
>>>> +        pool = srp_create_fr_pool(dev->dev, dev->pd,
>>>> +                      SRP_MDESC_PER_POOL, max_pages_per_mr);
>>> 1024 FRMRs per connection?! we use 1024 FMRs for all connections
>>> (per-device). I'd say that's a major over-allocation.
>> It depends on how many discontiguous I/O requests are submitted
>> concurrently. Anyway, how about limiting the number of memory regions to
>> the queue size ?
> 
> Perhaps, but we will need to reserve some more for discontinuous IOs.
> It is heuristic, for FS in most cases IO will align nicely, for some
> crazy DB applications - I'm not sure.

If srp_map_sg() runs out of memory descriptors it adds the remaining sg
entries to the SRP indirect descriptor without using memory
registration. In other words, I think a queue full of discontiguous I/O
requests should be handled properly by srp_map_sg().

Bart.
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