RE: [PATCH rdma-next] RDMA/irdma: Add support for address handle re-use

["Saleem, Shiraz" <shiraz.saleem@intel.com>]

> Subject: Re: [PATCH rdma-next] RDMA/irdma: Add support for address handle re-
> use
> 
> On Thu, Jan 20, 2022 at 11:40:41AM -0600, Shiraz Saleem wrote:
> > +/**
> > + * irdma_ah_exists - Check for existing identical AH
> > + * @iwdev: irdma device
> > + * @new_ah: AH to check for
> > + *
> > + * returns true if AH is found, false if not found.
> > + */
> > +static bool irdma_ah_exists(struct irdma_device *iwdev,
> > +			    struct irdma_ah *new_ah)
> > +{
> > +	struct irdma_ah *ah;
> >
> > -		if (!cnt) {
> > -			ibdev_dbg(&iwdev->ibdev,
> > -				  "VERBS: CQP create AH timed out");
> > -			err = -ETIMEDOUT;
> > -			goto error;
> > +	list_for_each_entry (ah, &iwdev->ah_list, list) {
> > +		/* Set ah_valid and ah_id the same so memcmp can work */
> > +		new_ah->sc_ah.ah_info.ah_idx = ah->sc_ah.ah_info.ah_idx;
> > +		new_ah->sc_ah.ah_info.ah_valid = ah->sc_ah.ah_info.ah_valid;
> > +		if (!memcmp(&ah->sc_ah.ah_info, &new_ah->sc_ah.ah_info,
> > +			    sizeof(ah->sc_ah.ah_info))) {
> > +			refcount_inc(&ah->refcnt);
> > +			new_ah->parent_ah = ah;
> > +			return true;
> >  		}
> >  	}
> 
> So, the number of AHs is so large the HW has problems but you propose to use a
> linear search to de-dup them?

We will look into optimizing this search. 

> 
> > +static int irdma_create_user_ah(struct ib_ah *ibah,
> > +				struct rdma_ah_init_attr *attr,
> > +				struct ib_udata *udata)
> > +{
> > +	struct irdma_ah *ah = container_of(ibah, struct irdma_ah, ibah);
> > +	struct irdma_device *iwdev = to_iwdev(ibah->pd->device);
> > +	struct irdma_create_ah_resp uresp;
> > +	struct irdma_ah *parent_ah;
> > +	int err;
> > +
> > +	err = irdma_setup_ah(ibah, attr);
> > +	if (err)
> > +		return err;
> > +	if (attr->flags & RDMA_CREATE_AH_SLEEPABLE) {
> > +		mutex_lock(&iwdev->ah_list_lock);
> 
> User AH's are always sleepable, no need for these extra paths.
>

Ok.

Thanks a lot for the feedback.

Shiraz