linux-kernel - Re: [PATCH v1 1/1] rxe: calculate inline data size based on requested values

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Date:   Tue, 29 Oct 2019 12:31:03 -0700
From:   Rao Shoaib <rao.shoaib@...cle.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     monis@...lanox.com, dledford@...hat.com, sean.hefty@...el.com,
        hal.rosenstock@...il.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] rxe: calculate inline data size based on requested
 values

Hi Jason,

Thanks for the comments, please see inline.

On 10/29/19 12:11 PM, Jason Gunthorpe wrote:
> On Wed, Oct 23, 2019 at 10:32:37AM -0700, rao Shoaib wrote:
>> From: Rao Shoaib <rao.shoaib@...cle.com>
>>
>> rxe driver has a hard coded value for the size of inline data, where as
>> mlx5 driver calculates number of SGE's and inline data size based on the
>> values in the qp request. This patch modifies rxe driver to do the same
>> so that applications can work seamlessly across drivers.
> This description doesn't seem accurate at all, and this patch seems to
> be doing two things:
I thought the note described the change, I will try harder next time.
>
>> Signed-off-by: Rao Shoaib <rao.shoaib@...cle.com>
>> ---
>>   drivers/infiniband/sw/rxe/rxe_param.h | 2 +-
>>   drivers/infiniband/sw/rxe/rxe_qp.c    | 4 ++++
>>   2 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_param.h b/drivers/infiniband/sw/rxe/rxe_param.h
>> index 1b596fb..657f9303 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_param.h
>> +++ b/drivers/infiniband/sw/rxe/rxe_param.h
>> @@ -68,7 +68,6 @@ enum rxe_device_param {
>>   	RXE_HW_VER			= 0,
>>   	RXE_MAX_QP			= 0x10000,
>>   	RXE_MAX_QP_WR			= 0x4000,
>> -	RXE_MAX_INLINE_DATA		= 400,
>>   	RXE_DEVICE_CAP_FLAGS		= IB_DEVICE_BAD_PKEY_CNTR
>>   					| IB_DEVICE_BAD_QKEY_CNTR
>>   					| IB_DEVICE_AUTO_PATH_MIG
>> @@ -81,6 +80,7 @@ enum rxe_device_param {
>>   					| IB_DEVICE_MEM_MGT_EXTENSIONS,
>>   	RXE_MAX_SGE			= 32,
>>   	RXE_MAX_SGE_RD			= 32,
>> +	RXE_MAX_INLINE_DATA		= RXE_MAX_SGE * sizeof(struct ib_sge),
>>   	RXE_MAX_CQ			= 16384,
>>   	RXE_MAX_LOG_CQE			= 15,
>>   	RXE_MAX_MR			= 2 * 1024,
> Increasing RXE_MAX_INLINE_DATA to match the WQE size limited the
> MAX_SGE. IMHO this is done in a hacky way, instead we should define a
> maximim WQE size and from there derive the MAX_INLINE_DATA and MAX_SGE
> limitations.
There was already RXE_MAX_SGE defined so I did not define MAX_WQE. If 
that is what is preference I can submit a patch with that. What is a 
good value for MAX_WQE?
>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_qp.c b/drivers/infiniband/sw/rxe/rxe_qp.c
>> index aeea994..45b5da5 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_qp.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_qp.c
>> @@ -229,6 +229,7 @@ static int rxe_qp_init_req(struct rxe_dev *rxe, struct rxe_qp *qp,
>>   {
>>   	int err;
>>   	int wqe_size;
>> +	unsigned int inline_size;
>>   
>>   	err = sock_create_kern(&init_net, AF_INET, SOCK_DGRAM, 0, &qp->sk);
>>   	if (err < 0)
>> @@ -244,6 +245,9 @@ static int rxe_qp_init_req(struct rxe_dev *rxe, struct rxe_qp *qp,
>>   			 sizeof(struct rxe_send_wqe) +
>>   			 qp->sq.max_inline);
>>   
>> +	inline_size = wqe_size - sizeof(struct rxe_send_wqe);
>> +	qp->sq.max_inline = inline_size;
>> +	init->cap.max_inline_data = inline_size;
> Whatever this is doing. Is this trying to expand the supported inline
> data when max_sge is provided? That seems reasonable but
> peculiar. Should be it's own patch.
Yes that is what it is dong same as mlx5 which takes the larger of the 
two values reqquested and bumps the other. I will submit a separate patch.
>
> Also don't double initialize qp->sq.max_inline in the same function,
> and there is no need for the temporary 'inline_size'

I used a separate variable as I would have to repeat the calculation 
twice. I do not understand your comment about double initialization, can 
you please clarify that for me.

Thanks,

Shoaib

>
> Jason
>
>
>>   	qp->sq.queue = rxe_queue_init(rxe,
>>   				      &qp->sq.max_wr,
>>   				      wqe_size);
>> -- 
>> 1.8.3.1
>>