Re: [RFC RESEND 16/16] nvme-pci: use blk_rq_dma_map() for NVMe SGL

Zhu Yanjun
2024-05-06T07:25:09Z

On 05.05.24 15:23, Leon Romanovsky wrote:
> On Fri, May 03, 2024 at 04:41:21PM +0200, Zhu Yanjun wrote:
>> On 05.03.24 12:18, Leon Romanovsky wrote:
>>> From: Chaitanya Kulkarni <kch@nvidia.com>
> <...>
>
>>> This is an RFC to demonstrate the newly added DMA APIs can be used to
>>> map/unmap bvecs without the use of sg list, hence I've modified the pci
>>> code to only handle SGLs for now. Once we have some agreement on the
>>> structure of new DMA API I'll add support for PRPs along with all the
>>> optimization that I've removed from the code for this RFC for NVMe SGLs
>>> and PRPs.
>>>
> <...>
>
>>> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
>>> index e6267a6aa380..140939228409 100644
>>> --- a/drivers/nvme/host/pci.c
>>> +++ b/drivers/nvme/host/pci.c
>>> @@ -236,7 +236,9 @@ struct nvme_iod {
>>> unsigned int dma_len; /* length of single DMA segment mapping */
>>> dma_addr_t first_dma;
>>> dma_addr_t meta_dma;
>>> - struct sg_table sgt;
>>> + struct dma_iova_attrs iova;
>>> + dma_addr_t dma_link_address[128];
>> Why the length of this array is 128? Can we increase this length of the
>> array?
> It is combination of two things:
> * Good enough value for this nvme RFC to pass simple test, which Chaitanya did.
> * Output of various NVME_CTRL_* defines

Thanks a lot. I enlarged this number to 512. It seems that it can work.
Hope this will increase the performance.

Best Regards,

Zhu Yanjun

>
> Thanks

--
Best Regards,
Yanjun.Zhu