linux-kernel - Re: [PATCH for-next 4/6] RDMA/hns: Support flexible pagesize

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Date: Tue, 26 Dec 2023 11:42:18 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Junxian Huang <huangjunxian6@...ilicon.com>
Cc: jgg@...pe.ca, linux-rdma@...r.kernel.org, linuxarm@...wei.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH for-next 4/6] RDMA/hns: Support flexible pagesize

On Tue, Dec 26, 2023 at 05:16:33PM +0800, Junxian Huang wrote:
> 
> 
> On 2023/12/26 16:52, Leon Romanovsky wrote:
> > On Mon, Dec 25, 2023 at 03:53:28PM +0800, Junxian Huang wrote:
> >> From: Chengchang Tang <tangchengchang@...wei.com>
> >>
> >> In the current implementation, a fixed page size is used to
> >> configure the PBL, which is not flexible enough and is not
> >> conducive to the performance of the HW.
> >>
> >> Signed-off-by: Chengchang Tang <tangchengchang@...wei.com>
> >> Signed-off-by: Junxian Huang <huangjunxian6@...ilicon.com>
> >> ---
> >>  drivers/infiniband/hw/hns/hns_roce_alloc.c  |   6 -
> >>  drivers/infiniband/hw/hns/hns_roce_device.h |   9 ++
> >>  drivers/infiniband/hw/hns/hns_roce_mr.c     | 168 +++++++++++++++-----
> >>  3 files changed, 139 insertions(+), 44 deletions(-)
> > 
> > I'm wonder if the ib_umem_find_best_pgsz() API should be used instead.
> > What is missing there?
> > 
> > Thanks
> 
> Actually this API is used for umem.
> For kmem, we add hns_roce_find_buf_best_pgsz() to do a similar job.

Thanks, let's give a chance to Jason to provide his feedback. I have a
strong feeling that this code duplicates something in the kernel.

Thanks

> 
> +static int get_best_page_shift(struct hns_roce_dev *hr_dev,
> +			       struct hns_roce_mtr *mtr,
> +			       struct hns_roce_buf_attr *buf_attr)
> +{
> +	unsigned int page_sz;
> +
> +	if (!buf_attr->adaptive || buf_attr->type != MTR_PBL)
> +		return 0;
> +
> +	if (mtr->umem)
> +		page_sz = ib_umem_find_best_pgsz(mtr->umem,
> +						 hr_dev->caps.page_size_cap,
> +						 buf_attr->iova);
> +	else
> +		page_sz = hns_roce_find_buf_best_pgsz(hr_dev, mtr->kmem);
> +
> +	if (!page_sz)
> +		return -EINVAL;
> +
> +	buf_attr->page_shift = order_base_2(page_sz);
> +	return 0;
> +}
> 
> Thanks,
> Junxian