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

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Message-ID: <CAC_iWjL04RRFCU13yejUONvvY0dzYO1scAzNOC+auWpFDctzAA@mail.gmail.com>
Date: Thu, 21 Dec 2023 08:37:46 +0200
From: Ilias Apalodimas <ilias.apalodimas@...aro.org>
To: Yunsheng Lin <linyunsheng@...wei.com>
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

Hi Yunsheng,

On Thu, 21 Dec 2023 at 04:07, Yunsheng Lin <linyunsheng@...wei.com> wrote:
>
> 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

I know, and that's exactly what my commit message explains.  Also,
that's the reason that the rename was 'frag_cnt' on v1.

/Ilias
>
> > 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
> > .
> >