Re: [PATCH 1/3] net/hns3: fix simple Tx path incorrect free the mbuf

[huangdengdui <huangdengdui@huawei.com>]

On 2025/1/9 0:57, Stephen Hemminger wrote:
> On Wed, 8 Jan 2025 10:40:43 +0800
> Jie Hai <haijie1@huawei.com> wrote:
> 
>> On 2024/12/31 1:55, Stephen Hemminger wrote:
>>> On Mon, 30 Dec 2024 14:54:03 +0800
>>> Jie Hai <haijie1@huawei.com> wrote:
>>>   
>>>> From: Jie Hai <haijie1@huawei.com>
>>>> To: <dev@dpdk.org>, <thomas@monjalon.net>, <ferruh.yigit@amd.com>,  <david.marchand@redhat.com>, <andrew.rybchenko@oktetlabs.ru>, Chengwen Feng  <fengchengwen@huawei.com>, "Wei Hu (Xavier)" <xavier.huwei@huawei.com>,  Huisong Li <lihuisong@huawei.com>
>>>> CC: <haijie1@huawei.com>, <huangdengdui@huawei.com>
>>>> Subject: [PATCH 1/3] net/hns3: fix simple Tx path incorrect free the mbuf
>>>> Date: Mon, 30 Dec 2024 14:54:03 +0800
>>>> X-Mailer: git-send-email 2.22.0
>>>>
>>>> From: Dengdui Huang <huangdengdui@huawei.com>
>>>>
>>>> When RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE offload is not set,
>>>> use rte_pktmbuf_free_seg() to free the mbuf.
>>>>
>>>> Fixes: 7ef933908f04 ("net/hns3: add simple Tx path")
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Dengdui Huang <huangdengdui@huawei.com>
>>>> Signed-off-by: Jie Hai <haijie1@huawei.com>  
>>>
>>> What about the fast free case which is using rte_mempool_put_bulk when
>>> it should use rte_pktmbuf_free_bulk instead?
>>>
>>>   
>> Hi, Stephen Hemminger,
>>
>> During the fast free case, the performance of using
>> rte_mempool_put_bulk is higher than that of using
>> rte_pktmbuf_free_bulk because other references
>> to mbuf do not need to be considered. So it's better
>>   to not change.
>>
>> Thanks,
>> Jie Hai
> 
> The problem is that having an open coded version of this buried in
> one driver is a long term potential proble>
> If you really think that optimizing free like this is noticeable, then
> why not make a new function "rte_pktmuf_fast_free_bulk" and put it in the
> regular mbuf library.
> 

Do you mean to add the following functions to the library?

void rte_pktmbuf_fast_free_bulk(struct rte_mbuf **mbufs, unsigned int count)
{
	rte_mempool_put_bulk(mbufs[0]->pool, (void **)mbufs, count);
}

The driver uses rte_mempool_put_bulk only when the following conditions are met:
1. All mbufs comes from the same mempool
2. All mbufs have only one reference.
3. All mbufs have only one segment.
So the rte_pktmbuf_fast_free_bulk function is just a wrapper around the rte_mempool_put_bulk function.