linux-kernel - Re: [RFC PATCH net-next] net/smc: Introduce receive queue flow control support

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Message-ID: <0b73df73-d5e8-32a8-1495-63596b256392@linux.alibaba.com>
Date:   Sat, 22 Jan 2022 00:48:32 +0800
From:   Guangguan Wang <guangguan.wang@...ux.alibaba.com>
To:     Tony Lu <tonylu@...ux.alibaba.com>
Cc:     kgraul@...ux.ibm.com, davem@...emloft.net, kuba@...nel.org,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next] net/smc: Introduce receive queue flow
 control support

On 2022/1/20 22:22, Tony Lu wrote:>>  #include "smc_ib.h"
>>  
>> -#define SMC_RMBS_PER_LGR_MAX	255	/* max. # of RMBs per link group */
>> +#define SMC_RMBS_PER_LGR_MAX	32	/* max. # of RMBs per link group. Correspondingly,
>> +					 * SMC_WR_BUF_CNT should not be less than 2 *
>> +					 * SMC_RMBS_PER_LGR_MAX, since every connection at
>> +					 * least has two rq/sq credits in average, otherwise
>> +					 * may result in waiting for credits in sending process.
>> +					 */
> 
> This gives a fixed limit for per link group connections. Using tunable
> knobs to control this for different workload would be better. It also
> reduce the completion of free slots in the same link group and link.
> 

It is a good idea, but I find a patch (https://lore.kernel.org/linux-s390/20220114054852.38058-7-tonylu@linux.alibaba.com/) where you have already done this idea.