Received-SPF: pass (google.com: domain of linux-kernel+bounces-7743-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Subject: Re: [PATCH net-next] page_pool: Rename frag_users to frag_cnt
To: Ilias Apalodimas <ilias.apalodimas@linaro.org>
CC: <netdev@vger.kernel.org>, Jesper Dangaard Brouer <hawk@kernel.org>, "David
 S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Jakub
 Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	<linux-kernel@vger.kernel.org>
References: <20231215073119.543560-1-ilias.apalodimas@linaro.org>
 <6fddeb22-0906-e04c-3a84-7836bef9ffa2@huawei.com>
 <CAC_iWjLiOdUqLmRHjZmwv9QBsBvYNV=zn30JrRbJa05qMyDBmw@mail.gmail.com>
 <fb0f33d8-d09a-57fc-83b0-ccf152277355@huawei.com>
 <CAC_iWjKH5ZCUwVWc2EisfjeLVF=ko967hqpdAc7G4FdsZCq7NA@mail.gmail.com>
From: Yunsheng Lin <linyunsheng@huawei.com>
Message-ID: <d853acde-7d69-c715-4207-fb77da1fb203@huawei.com>
Date: Thu, 21 Dec 2023 10:07:26 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.0
Precedence: bulk
MIME-Version: 1.0
In-Reply-To: <CAC_iWjKH5ZCUwVWc2EisfjeLVF=ko967hqpdAc7G4FdsZCq7NA@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 7bit

On 2023/12/20 15:56, Ilias Apalodimas wrote:
> Hi Yunsheng,
>>>>>  #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
> 
> This is still a bit confusing for me since the actual bias is the
> number of fragments that you initially split the page. But I am fine
Acctually there are two bais numbers for a page used by
page_pool_alloc_frag().
the one for page->pp_ref_count, which already use the BIAS_MAX, which
indicates the initial bais number:
https://elixir.bootlin.com/linux/latest/source/net/core/page_pool.c#L779

Another one for pool->frag_users indicating the runtime bais number, which
need changing when a page is split into more fragments:
https://elixir.bootlin.com/linux/latest/source/net/core/page_pool.c#L776
https://elixir.bootlin.com/linux/latest/source/net/core/page_pool.c#L783

> with having a common approach. I'll send the rename again shortly, and
> I can send the logic invert a bit later (or feel free to send it,
> since it was your idea).
> 
> Thanks
> /Ilias
> .
>