Re: [PATCH rdma-next v1 2/2] RDMA/core: Optimize XRC target lookup

[Maor Gottlieb <maorg@mellanox.com>]

On 6/23/2020 9:49 PM, Jason Gunthorpe wrote:
> On Tue, Jun 23, 2020 at 09:15:06PM +0300, Leon Romanovsky wrote:
>> On Tue, Jun 23, 2020 at 02:52:00PM -0300, Jason Gunthorpe wrote:
>>> On Tue, Jun 23, 2020 at 02:15:31PM +0300, Leon Romanovsky wrote:
>>>> From: Maor Gottlieb <maorg@mellanox.com>
>>>>
>>>> Replace the mutex with read write semaphore and use xarray instead
>>>> of linked list for XRC target QPs. This will give faster XRC target
>>>> lookup. In addition, when QP is closed, don't insert it back to the
>>>> xarray if the destroy command failed.
>>>>
>>>> Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
>>>> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
>>>>   drivers/infiniband/core/verbs.c | 57 ++++++++++++---------------------
>>>>   include/rdma/ib_verbs.h         |  5 ++-
>>>>   2 files changed, 23 insertions(+), 39 deletions(-)
>>>>
>>>> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
>>>> index d66a0ad62077..1ccbe43e33cd 100644
>>>> +++ b/drivers/infiniband/core/verbs.c
>>>> @@ -1090,13 +1090,6 @@ static void __ib_shared_qp_event_handler(struct ib_event *event, void *context)
>>>>   	spin_unlock_irqrestore(&qp->device->qp_open_list_lock, flags);
>>>>   }
>>>>
>>>> -static void __ib_insert_xrcd_qp(struct ib_xrcd *xrcd, struct ib_qp *qp)
>>>> -{
>>>> -	mutex_lock(&xrcd->tgt_qp_mutex);
>>>> -	list_add(&qp->xrcd_list, &xrcd->tgt_qp_list);
>>>> -	mutex_unlock(&xrcd->tgt_qp_mutex);
>>>> -}
>>>> -
>>>>   static struct ib_qp *__ib_open_qp(struct ib_qp *real_qp,
>>>>   				  void (*event_handler)(struct ib_event *, void *),
>>>>   				  void *qp_context)
>>>> @@ -1139,16 +1132,15 @@ struct ib_qp *ib_open_qp(struct ib_xrcd *xrcd,
>>>>   	if (qp_open_attr->qp_type != IB_QPT_XRC_TGT)
>>>>   		return ERR_PTR(-EINVAL);
>>>>
>>>> -	qp = ERR_PTR(-EINVAL);
>>>> -	mutex_lock(&xrcd->tgt_qp_mutex);
>>>> -	list_for_each_entry(real_qp, &xrcd->tgt_qp_list, xrcd_list) {
>>>> -		if (real_qp->qp_num == qp_open_attr->qp_num) {
>>>> -			qp = __ib_open_qp(real_qp, qp_open_attr->event_handler,
>>>> -					  qp_open_attr->qp_context);
>>>> -			break;
>>>> -		}
>>>> +	down_read(&xrcd->tgt_qps_rwsem);
>>>> +	real_qp = xa_load(&xrcd->tgt_qps, qp_open_attr->qp_num);
>>>> +	if (!real_qp) {
>>> Don't we already have a xarray indexed against qp_num in res_track?
>>> Can we use it somehow?
>> We don't have restrack for XRC, we will need somehow manage QP-to-XRC
>> connection there.
> It is not xrc, this is just looking up a qp and checking if it is part
> of the xrcd
>
> Jason


It's the XRC target  QP and it is not tracked.