netdev - Re: 答复: [PATCH] page_pool: mark unbound node page as reusable pages

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Date:   Thu, 5 Dec 2019 09:43:53 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     "Li,Rongqing" <lirongqing@...du.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "saeedm@...lanox.com" <saeedm@...lanox.com>
Subject: Re: 答复: [PATCH] page_pool: mark unbound node page as reusable pages

On 2019/12/5 9:08, Li,Rongqing wrote:
> 
> 
>> -----邮件原件-----
>> 发件人: Yunsheng Lin [mailto:linyunsheng@...wei.com]
>> 发送时间: 2019年12月5日 8:55
>> 收件人: Li,Rongqing <lirongqing@...du.com>; netdev@...r.kernel.org;
>> saeedm@...lanox.com
>> 主题: Re: [PATCH] page_pool: mark unbound node page as reusable pages
>>
>> On 2019/12/4 18:14, Li RongQing wrote:
>>> some drivers uses page pool, but not require to allocate page from
>>> bound node, so pool.p.nid is NUMA_NO_NODE, and this fixed patch will
>>> block this kind of driver to recycle
>>>
>>> Fixes: d5394610b1ba ("page_pool: Don't recycle non-reusable pages")
>>> Signed-off-by: Li RongQing <lirongqing@...du.com>
>>> Cc: Saeed Mahameed <saeedm@...lanox.com>
>>> ---
>>>  net/core/page_pool.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/core/page_pool.c b/net/core/page_pool.c index
>>> a6aefe989043..4054db683178 100644
>>> --- a/net/core/page_pool.c
>>> +++ b/net/core/page_pool.c
>>> @@ -317,7 +317,9 @@ static bool __page_pool_recycle_direct(struct page
>> *page,
>>>   */
>>>  static bool pool_page_reusable(struct page_pool *pool, struct page
>>> *page)  {
>>> -	return !page_is_pfmemalloc(page) && page_to_nid(page) == pool->p.nid;
>>> +	return !page_is_pfmemalloc(page) &&
>>> +		(page_to_nid(page) == pool->p.nid ||
>>> +		 pool->p.nid == NUMA_NO_NODE);
>>
>> If I understand it correctly, you are allowing recycling when
>> pool->p.nid is NUMA_NO_NODE, which does not seems match the commit
>> log: "this fixed patch will block this kind of driver to recycle".
>>
>> Maybe you mean "commit d5394610b1ba" by this fixed patch?
> 
> yes
> 
>>
>> Also, maybe it is better to allow recycling if the below condition is matched:
>>
>> 	pool->p.nid == NUMA_NO_NODE && page_to_nid(page) ==
>> numa_mem_id()
> 
> If driver uses NUMA_NO_NODE, it does not care numa node, and maybe its platform
> Only has a node, so not need to compare like "page_to_nid(page) ==  numa_mem_id()"

Normally, driver does not care if the node of a device is NUMA_NO_NODE or not, it
just uses the node that returns from dev_to_node().

Even for multi node system, the node of a device may be NUMA_NO_NODE when
BIOS/FW has not specified it through ACPI/DT, see [1].


[1] https://lore.kernel.org/patchwork/patch/1141952/

> 
> 
> -RongQing
> 
> 
>>
>>>  }
>>>
>>>  void __page_pool_put_page(struct page_pool *pool, struct page *page,
>>>
>