[rds-devel] RDS - resource leakage - recv_ring counters - looks buggy

[Viral Mehta]

Hi Andy,
Thanks for your response.

Yes, I agree with you. rdma_disconnect should free up all SQ and RQ 
WQEs. Also iwarp sepc confirms the same.

So, looks like RDS has no problem. I will let you know if I find 
something else.

Thanks again,

Andy Grover wrote:
> Viral Mehta wrote:
>   
>> I am, somehow, not able to forward this to netdev list.
>>
>> When we run any rds-ping test, it creates a connection. It sets up
>> QP. And then it posts (1024 or whatever mentioned through sysctl)
>> recvs. Basically these are pre-post recvs. Extra recvs will be posted
>> again if it goes below low-watermark.
>>
>> By design, Connection and all RDMA resources are destroyed only when
>> module is unloaded. Now in unloading process, before destroying RDMA
>> resources, it  waits till all send_ring/recv_ring becomes empty. 
>> =========== iw_cm.c:600:
>> wait_event(rds_iw_ring_empty_wait, iw_cm.c-601-
>> rds_iw_ring_empty(&ic->i_send_ring) && iw_cm.c-602-
>> rds_iw_ring_empty(&ic->i_recv_ring)); ===========
>>
>> Ring empty means diff (i.e., ring->w_alloc_ctr - ring->free_ctr)
>> should be zero. w_alloc_ctr are number of posted recvs and free_ctr
>> is number of recvs consumed. Ideally, this can never be zero as we
>> always want some pre-posted recvs and thus recv_ring will never be
>> empty.
>>     
>
> Hi Viral, sorry for the delay in responding.
>
> I believe what happens is that the rdma_disconnect() above the
> wait_event causes all the outstanding recv wrs to be completed with an
> error. This causes them to be freed. They are not refilled, and so the
> ring becomes empty.
>
> Does this analysis appear correct to you?
>
> Thanks -- Regards -- Andy
>
>
>
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>
>   
-- 
Thanks, Viral Mehta, Embedded Software Engineer, www.einfochips.com