netdev - Re: [PATCH net-next v3 12/18] net/smc: implement DMB-related operations of loopback

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Message-ID: <d6facfd5-e083-ffc7-05e5-2e8f3ef17735@linux.alibaba.com>
Date: Fri, 22 Sep 2023 15:42:45 +0800
From: Wen Gu <guwen@...ux.alibaba.com>
To: Wenjia Zhang <wenjia@...ux.ibm.com>, kgraul@...ux.ibm.com,
 jaka@...ux.ibm.com, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com
Cc: alibuda@...ux.alibaba.com, tonylu@...ux.alibaba.com,
 linux-s390@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 12/18] net/smc: implement DMB-related
 operations of loopback



On 2023/9/22 07:31, Wenjia Zhang wrote:
> 
> 

<...>

>> +static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
>> +                   void *client_priv)
>> +{
>> +    struct smc_lo_dmb_node *dmb_node, *tmp_node;
>> +    struct smc_lo_dev *ldev = smcd->priv;
>> +    int sba_idx, rc;
>> +
>> +    /* check space for new dmb */
>> +    for_each_clear_bit(sba_idx, ldev->sba_idx_mask, SMC_LODEV_MAX_DMBS) {
>> +        if (!test_and_set_bit(sba_idx, ldev->sba_idx_mask))
>> +            break;
>> +    }
>> +    if (sba_idx == SMC_LODEV_MAX_DMBS)
>> +        return -ENOSPC;
>> +
>> +    dmb_node = kzalloc(sizeof(*dmb_node), GFP_KERNEL);
>> +    if (!dmb_node) {
>> +        rc = -ENOMEM;
>> +        goto err_bit;
>> +    }
>> +
>> +    dmb_node->sba_idx = sba_idx;
>> +    dmb_node->cpu_addr = kzalloc(dmb->dmb_len, GFP_KERNEL |
>> +                     __GFP_NOWARN | __GFP_NORETRY |
>> +                     __GFP_NOMEMALLOC);
> kzalloc()/kmalloc() allocates physically contigueous memory. Are you sure it is suitable for allocating the dmb?
> 

Yes, physically contigueous memory is little expensive here. I initially wanted to see the best performance.

I tried using vzalloc here, and the performance dropped a bit (2%~8%) compared to kzalloc. I think it is acceptable.

- ipc-benchmark
                        kzalloc                vzalloc
Message
rate (msg/s)            152076                 145753(-4.16%)

- sockperf
                        kzalloc                vzalloc
Bandwidth(MBps)       8491.638               8002.380(-5.76%)
Latency(us)              3.222                  3.508(+8.88%)

- nginx/wrk
                        kzalloc                vzalloc
Requests/s           272519.36              256490.94(-5.88%)

- redis-benchmark
                        kzalloc                vzalloc
GET(Requests/s)      123304.56              120084.05(-2.61%)
SET(Requests/s)      122062.87              118800.12(-2.67%)


>> +    if (!dmb_node->cpu_addr) {
>> +        rc = -ENOMEM;
>> +        goto err_node;
>> +    }
>> +    dmb_node->len = dmb->dmb_len;
>> +    dmb_node->dma_addr = (dma_addr_t)dmb_node->cpu_addr;
>> +
>> +again:
>> +    /* add new dmb into hash table */
>> +    get_random_bytes(&dmb_node->token, sizeof(dmb_node->token));
>> +    write_lock(&ldev->dmb_ht_lock);
>> +    hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_node->token) {
>> +        if (tmp_node->token == dmb_node->token) {
>> +            write_unlock(&ldev->dmb_ht_lock);
>> +            goto again;
>> +        }
>> +    }
>> +    hash_add(ldev->dmb_ht, &dmb_node->list, dmb_node->token);
>> +    write_unlock(&ldev->dmb_ht_lock);
>> +
>> +    dmb->sba_idx = dmb_node->sba_idx;
>> +    dmb->dmb_tok = dmb_node->token;
>> +    dmb->cpu_addr = dmb_node->cpu_addr;
>> +    dmb->dma_addr = dmb_node->dma_addr;
>> +    dmb->dmb_len = dmb_node->len;
>> +
>> +    return 0;
>> +
>> +err_node:
>> +    kfree(dmb_node);
>> +err_bit:
>> +    clear_bit(sba_idx, ldev->sba_idx_mask);
>> +    return rc;
>> +}
>> +
>> +static int smc_lo_unregister_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb)
>> +{
>> +    struct smc_lo_dmb_node *dmb_node = NULL, *tmp_node;
>> +    struct smc_lo_dev *ldev = smcd->priv;
>> +
>> +    /* remove dmb from hash table */
>> +    write_lock(&ldev->dmb_ht_lock);
>> +    hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb->dmb_tok) {
>> +        if (tmp_node->token == dmb->dmb_tok) {
>> +            dmb_node = tmp_node;
>> +            break;
>> +        }
>> +    }
>> +    if (!dmb_node) {
>> +        write_unlock(&ldev->dmb_ht_lock);
>> +        return -EINVAL;
>> +    }
>> +    hash_del(&dmb_node->list);
>> +    write_unlock(&ldev->dmb_ht_lock);
>> +
>> +    clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
>> +    kfree(dmb_node->cpu_addr);
>> +    kfree(dmb_node);
>> +
>> +    return 0;
>> +}
>> +