Re: [PATCH v2 2/2] RDMA/cm: Optimise rbtree searching

["Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>]

On 2021/5/12 22:26, Jason Gunthorpe wrote:
> On Wed, May 12, 2021 at 09:12:08PM +0800, Leizhen (ThunderTown) wrote:
>>
>>
>> On 2021/5/12 20:50, Jason Gunthorpe wrote:
>>> On Wed, May 12, 2021 at 06:05:37PM +0800, Zhen Lei wrote:
>>>>  static struct cm_id_private *cm_find_listen(struct ib_device *device,
>>>> @@ -686,22 +687,23 @@ static struct cm_id_private *cm_find_listen(struct ib_device *device,
>>>>  
>>>>  	while (node) {
>>>>  		cm_id_priv = rb_entry(node, struct cm_id_private, service_node);
>>>> -		if ((cm_id_priv->id.service_mask & service_id) ==
>>>> -		     cm_id_priv->id.service_id &&
>>>> -		    (cm_id_priv->id.device == device)) {
>>>> -			refcount_inc(&cm_id_priv->refcount);
>>>> -			return cm_id_priv;
>>>> -		}
>>>> +
>>>>  		if (device < cm_id_priv->id.device)
>>>>  			node = node->rb_left;
>>>>  		else if (device > cm_id_priv->id.device)
>>>>  			node = node->rb_right;
>>>> +		else if ((cm_id_priv->id.service_mask & service_id) == cm_id_priv->id.service_id)
>>>> +			goto found;
>>>>  		else if (be64_lt(service_id, cm_id_priv->id.service_id))
>>>>  			node = node->rb_left;
>>>>  		else
>>>>  			node = node->rb_right;
>>>>  	}
>>>
>>> This is not the pattern I showed you. Drop the first patch and rely on
>>> the implicit equality in the final else.
>>
>> Do you mean treate the "found" process as the else branch?
>>
>> But ((cm_id_priv->id.service_mask & service_id) ==
>> cm_id_priv->id.service_id) is different from (service_id ==
>> cm_id_priv->id.service_id),I'm just worried that it might change
>> the original logic.
> 
> The service_mask is always ~cpu_to_be64(0), it is some non-working
> dead code that has been left in here.
> 
> If you really want to touch this then you should have a prep patch to
> remove that entire API facet, then the above will make sense.

Okay, I'll try.

> 
> Jason
> 
> .
>