linux-kernel - Re: [PATCH rdma-next 2/5] RDMA/hns: Modify uar allocation algorithm to avoid bitmap exhaust

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Date:   Wed, 23 May 2018 14:49:35 +0800
From:   "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     <dledford@...hat.com>, <jgg@...pe.ca>,
        <linux-rdma@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <xavier.huwei@....com>, <lijun_nudt@....com>
Subject: Re: [PATCH rdma-next 2/5] RDMA/hns: Modify uar allocation algorithm
 to avoid bitmap exhaust



On 2018/5/23 14:05, Leon Romanovsky wrote:
> On Thu, May 17, 2018 at 04:02:50PM +0800, Wei Hu (Xavier) wrote:
>> This patch modified uar allocation algorithm in hns_roce_uar_alloc
>> function to avoid bitmap exhaust.
>>
>> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@...wei.com>
>> ---
>>  drivers/infiniband/hw/hns/hns_roce_device.h |  1 +
>>  drivers/infiniband/hw/hns/hns_roce_pd.c     | 10 ++++++----
>>  2 files changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/infiniband/hw/hns/hns_roce_device.h b/drivers/infiniband/hw/hns/hns_roce_device.h
>> index 53c2f1b..412297d4 100644
>> --- a/drivers/infiniband/hw/hns/hns_roce_device.h
>> +++ b/drivers/infiniband/hw/hns/hns_roce_device.h
>> @@ -214,6 +214,7 @@ enum {
>>  struct hns_roce_uar {
>>  	u64		pfn;
>>  	unsigned long	index;
>> +	unsigned long	logic_idx;
>>  };
>>
>>  struct hns_roce_ucontext {
>> diff --git a/drivers/infiniband/hw/hns/hns_roce_pd.c b/drivers/infiniband/hw/hns/hns_roce_pd.c
>> index 4b41e04..b9f2c87 100644
>> --- a/drivers/infiniband/hw/hns/hns_roce_pd.c
>> +++ b/drivers/infiniband/hw/hns/hns_roce_pd.c
>> @@ -107,13 +107,15 @@ int hns_roce_uar_alloc(struct hns_roce_dev *hr_dev, struct hns_roce_uar *uar)
>>  	int ret = 0;
>>
>>  	/* Using bitmap to manager UAR index */
>> -	ret = hns_roce_bitmap_alloc(&hr_dev->uar_table.bitmap, &uar->index);
>> +	ret = hns_roce_bitmap_alloc(&hr_dev->uar_table.bitmap, &uar->logic_idx);
>>  	if (ret == -1)
>>  		return -ENOMEM;
>>
>> -	if (uar->index > 0)
>> -		uar->index = (uar->index - 1) %
>> +	if (uar->logic_idx > 0 && hr_dev->caps.phy_num_uars > 1)
>> +		uar->index = (uar->logic_idx - 1) %
>>  			     (hr_dev->caps.phy_num_uars - 1) + 1;
>> +	else
>> +		uar->index = 0;
>>
> Sorry, but maybe I didn't understand this change fully, but logic_idx is
> not initialized at all and one of two (needs to check your uar
> allocation): the logic_idx is always zero -> index will be zero too,
> or logic_idx is random variable -> index will be random too.
>
> What did you want to do?
>
Hi, Leon

    The prototype of hns_roce_bitmap_alloc as belows:
        int hns_roce_bitmap_alloc(struct hns_roce_bitmap *bitmap,
unsigned long *obj);
    In this statement,  we evaluate uar->logic_idx.
        ret = hns_roce_bitmap_alloc(&hr_dev->uar_table.bitmap,
&uar->logic_idx); 

    In hip06,  hr_dev->caps.phy_num_uars equals 8, 
        if (uar->logic_idx > 0) 
             uar-> index = 0;
       else
             uar-> index =(uar->logic_idx - 1) %
(hr_dev->caps.phy_num_uars - 1) + 1;   
    In hip08,  hr_dev->caps.phy_num_uars equals 1,  uar-> index = 0;

   Regards
Wei Hu
>>  	if (!dev_is_pci(hr_dev->dev)) {
>>  		res = platform_get_resource(hr_dev->pdev, IORESOURCE_MEM, 0);
>> @@ -132,7 +134,7 @@ int hns_roce_uar_alloc(struct hns_roce_dev *hr_dev, struct hns_roce_uar *uar)
>>
>>  void hns_roce_uar_free(struct hns_roce_dev *hr_dev, struct hns_roce_uar *uar)
>>  {
>> -	hns_roce_bitmap_free(&hr_dev->uar_table.bitmap, uar->index,
>> +	hns_roce_bitmap_free(&hr_dev->uar_table.bitmap, uar->logic_idx,
>>  			     BITMAP_NO_RR);
>>  }
>>
>> --
>> 1.9.1
>>