Re: [PATCH for-next] RDMA/hns: Create QP/CQ with selected QPN/CQN for bank load balance

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Sep 09, 2020 at 05:09:23PM +0800, Weihang Li wrote:
> From: Yangyang Li <liyangyang20@huawei.com>
> 
> In order to improve performance by balancing the load between different
> banks of cache, the QPC cache is desigend to choose one of 8 banks
> according to lower 3 bits of QPN, and the CQC cache uses the lower 2 bits
> to choose one from 4 banks. The hns driver needs to count the number of
> QP/CQ on each bank and then assigns the QP/CQ being created to the bank
> with the minimum load first.
> 
> Signed-off-by: Yangyang Li <liyangyang20@huawei.com>
> Signed-off-by: Weihang Li <liweihang@huawei.com>
>  drivers/infiniband/hw/hns/hns_roce_alloc.c  | 46 +++++++++++++++++++++++++++++
>  drivers/infiniband/hw/hns/hns_roce_cq.c     | 38 +++++++++++++++++++++++-
>  drivers/infiniband/hw/hns/hns_roce_device.h |  8 +++++
>  drivers/infiniband/hw/hns/hns_roce_qp.c     | 39 ++++++++++++++++++++++--
>  4 files changed, 128 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/hns/hns_roce_alloc.c b/drivers/infiniband/hw/hns/hns_roce_alloc.c
> index a522cb2..cbe955c 100644
> +++ b/drivers/infiniband/hw/hns/hns_roce_alloc.c
> @@ -36,6 +36,52 @@
>  #include "hns_roce_device.h"
>  #include <rdma/ib_umem.h>
>  
> +static int get_bit(struct hns_roce_bitmap *bitmap, u8 bankid,
> +		   u8 mod, unsigned long *obj)
> +{
> +	unsigned long offset_bak = bitmap->last;
> +	bool one_circle_flag = false;
> +
> +	do {
> +		*obj = find_next_zero_bit(bitmap->table, bitmap->max,
> +					  bitmap->last);
> +		if (*obj >= bitmap->max) {
> +			*obj = find_first_zero_bit(bitmap->table, bitmap->max);
> +			one_circle_flag = true;
> +		}
> +
> +		bitmap->last = (*obj + 1);
> +		if (bitmap->last == bitmap->max) {
> +			bitmap->last = 0;
> +			one_circle_flag = true;
> +		}
> +
> +		/* Not found after a round of search */
> +		if (bitmap->last >= offset_bak && one_circle_flag)
> +			return -EINVAL;
> +
> +	} while (*obj % mod != bankid);
> +
> +	return 0;
> +}

This looks like an ida, is there a reason it has to be open coded?

Jason