Re: [PATCH 8/8] IB/srp: Make queue size configurable

[Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 8/20/2013 8:43 PM, David Dillow wrote:
> On Tue, 2013-08-20 at 17:55 +0200, Bart Van Assche wrote:
>> On 08/20/13 17:34, Sagi Grimberg wrote:
>>> Question,
>>> If srp now will allow larger queues while using a single global FMR pool
>>> of size 1024, isn't it more likely now that in stress environment srp
>>> will run out of FMRs to handle IO commands?
>>> I mean that let's say that you have x scsi hosts with can_queue size of
>>> 512 (+-) and all of them are running IO stress, is it possible that all
>>> FMRs will be inuse and no FMR is available to register the next IO SG-list?
>>> Did you try out such a scenario?
>>>
>>> I guess that in such a case IB core will return EAGAIN and SRP will
>>> return SCSI_MLQUEUE_HOST_BUSY.
>>> I think it is a good Idea to move FMR pools to be per connection rather
>>> than a global pool, what do you think?
>> That makes sense to me. And as long as the above has not yet been
>> implemented I'm fine with dropping patch 8/8 from this patch set.
> Don't drop it; most configs won't have all that many connections and
> shouldn't have an issue; even those that do will only see a potential
> slowdown when running with everything at once.
>
> We can address the FMR/BMME issues on top of this patch.

Agree.
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