netdev - Re: [PATCH net-next] page_pool: Rename frag_users to frag

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Date: Fri, 15 Dec 2023 20:34:05 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Ilias Apalodimas <ilias.apalodimas@...aro.org>
CC: <netdev@...r.kernel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] page_pool: Rename frag_users to frag_cnt

On 2023/12/15 19:58, Ilias Apalodimas wrote:
> Hi Yunsheng,
> 
> On Fri, 15 Dec 2023 at 13:10, Yunsheng Lin <linyunsheng@...wei.com> wrote:
>>
>> On 2023/12/15 15:31, Ilias Apalodimas wrote:
>>> Since [0] got merged, it's clear that 'pp_ref_count' is used to track
>>> the number of users for each page. On struct_page though we have
>>> a member called 'frag_users'. Despite of what the name suggests this is
>>> not the number of users. It instead represents the number of fragments of
>>> the current page. When we have a single page this is set to one. When we
>>> split the page this is set to the actual number of frags and later used
>>> in page_pool_drain_frag() to infer the real number of users.
>>>
>>> So let's rename it to something that matches the description above
>>>
>>> [0]
>>> Link: https://lore.kernel.org/netdev/20231212044614.42733-2-liangchen.linux@gmail.com/
>>> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
>>> ---
>>>  include/net/page_pool.h | 2 +-
>>>  net/core/page_pool.c    | 8 ++++----
>>>  2 files changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
>>> index 813c93499f20..957cd84bb3f4 100644
>>> --- a/include/net/page_pool.h
>>> +++ b/include/net/page_pool.h
>>> @@ -158,7 +158,7 @@ struct page_pool {
>>>       u32 pages_state_hold_cnt;
>>>       unsigned int frag_offset;
>>>       struct page *frag_page;
>>> -     long frag_users;
>>> +     long frag_cnt;
>>
>> I would rename it to something like refcnt_bais to mirror the pagecnt_bias
>> in struct page_frag_cache.
> 
> Sure
> 
>>
>>>
>>>  #ifdef CONFIG_PAGE_POOL_STATS
>>>       /* these stats are incremented while in softirq context */
>>> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
>>> index 9b203d8660e4..19a56a52ac8f 100644
>>> --- a/net/core/page_pool.c
>>> +++ b/net/core/page_pool.c
>>> @@ -659,7 +659,7 @@ EXPORT_SYMBOL(page_pool_put_page_bulk);
>>>  static struct page *page_pool_drain_frag(struct page_pool *pool,
>>>                                        struct page *page)
>>>  {
>>> -     long drain_count = BIAS_MAX - pool->frag_users;
>>> +     long drain_count = BIAS_MAX - pool->frag_cnt;
>>
>> drain_count = pool->refcnt_bais;
> 
> I think this is a typo right? This still remains

It would be better to invert logic too, as it is mirroring:

https://elixir.bootlin.com/linux/v6.7-rc5/source/mm/page_alloc.c#L4745