netdev - Re: [PATCH rdma-next 3/3] RDMA/rw: Support threshold for registration vs scattering to local pages

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Date:   Mon, 7 Oct 2019 13:07:02 +0300
From:   Max Gurtovoy <maxg@...lanox.com>
To:     Leon Romanovsky <leon@...nel.org>,
        Christoph Hellwig <hch@...radead.org>
CC:     Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Yamin Friedman <yaminf@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH rdma-next 3/3] RDMA/rw: Support threshold for registration
 vs scattering to local pages


On 10/7/2019 10:54 AM, Leon Romanovsky wrote:
> On Sun, Oct 06, 2019 at 11:58:25PM -0700, Christoph Hellwig wrote:
>>>   /*
>>> - * Check if the device might use memory registration.  This is currently only
>>> - * true for iWarp devices. In the future we can hopefully fine tune this based
>>> - * on HCA driver input.
>>> + * Check if the device might use memory registration.
>>>    */
>> Please keep the important bits of this comments instead of just
>> removing them.
>>
>>>   {
>>> @@ -30,6 +28,8 @@ static inline bool rdma_rw_can_use_mr(struct ib_device *dev, u8 port_num)
>>>   		return true;
>>>   	if (unlikely(rdma_rw_force_mr))
>>>   		return true;
>>> +	if (dev->attrs.max_sgl_rd)
>>> +		return true;
>> Logically this should go before the rdma_rw_force_mr check.
>>
>>>   	if (unlikely(rdma_rw_force_mr))
>>>   		return true;
>>> +	if (dev->attrs.max_sgl_rd && dir == DMA_FROM_DEVICE
>>> +	    && dma_nents > dev->attrs.max_sgl_rd)
>> Wrong indendation.  The && belongs on the first line.  And again, this
>> logically belongs before the rdma_rw_force_mr check.
> I'll fix.
>
> Thanks

The above comments looks reasonable.

Nice optimization Yamin.