netdev - Re: [PATCH net-next v3] net/smc: Use percpu ref for wr tx reference

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Date:   Mon, 13 Mar 2023 11:46:07 +0800
From:   Kai <KaiShen@...ux.alibaba.com>
To:     Tony Lu <tonylu@...ux.alibaba.com>
Cc:     kgraul@...ux.ibm.com, wenjia@...ux.ibm.com, jaka@...ux.ibm.com,
        kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next v3] net/smc: Use percpu ref for wr tx reference



On 3/13/23 9:20 AM, Kai wrote:
> 
> 
> On 3/8/23 4:30 PM, Tony Lu wrote:
>>> redis-benchmark on smc-r with atomic wr_tx_refcnt:
>>> SET: 525817.62 requests per second, p50=0.087 msec
>>> GET: 570841.44 requests per second, p50=0.087 msec
>>>
>>> redis-benchmark on the percpu_ref version:
>>> SET: 539956.81 requests per second, p50=0.087 msec
>>> GET: 587613.12 requests per second, p50=0.079 msec
>>
>> Does the test data need to be refreshed?
>>
> Will do.
>>> diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
>>> index 08b457c2d294..1645fba0d2d3 100644
>>> --- a/net/smc/smc_core.h
>>> +++ b/net/smc/smc_core.h
>>> @@ -106,7 +106,10 @@ struct smc_link {
>>>       unsigned long        *wr_tx_mask;    /* bit mask of used 
>>> indexes */
>>>       u32            wr_tx_cnt;    /* number of WR send buffers */
>>>       wait_queue_head_t    wr_tx_wait;    /* wait for free WR send 
>>> buf */
>>> -    atomic_t        wr_tx_refcnt;    /* tx refs to link */
>>> +    struct {
>>> +        struct percpu_ref    wr_tx_refs;
>>> +    } ____cacheline_aligned_in_smp;
>>> +    struct completion    tx_ref_comp;
>>
>> For the variable names suffixed with wr_*_refs, should we continue to
>> use wr_*_refcnt?
>>
>> Thanks.
> In my opinion, we can't get the count of the percpu reference until it 
> we start to destroy it. So maybe using wr_*_refcnt here is more 
> appropriate？
I mean wr_*_refs here. Sorry for the mistake.