netdev - Re: [PATCH v6 net-next 4/5] net: page_pool: make stats available just for global pools

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Date: Tue, 30 Jan 2024 17:01:50 +0100
From: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Yunsheng Lin <linyunsheng@...wei.com>,
	Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org,
	davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
	pabeni@...hat.com, bpf@...r.kernel.org, toke@...hat.com,
	willemdebruijn.kernel@...il.com, jasowang@...hat.com,
	sdf@...gle.com, ilias.apalodimas@...aro.org
Subject: Re: [PATCH v6 net-next 4/5] net: page_pool: make stats available
 just for global pools

> 
> 
> On 30/01/2024 14.52, Lorenzo Bianconi wrote:
> > > On 2024/1/29 21:07, Lorenzo Bianconi wrote:
> > > > > On 2024/1/28 22:20, Lorenzo Bianconi wrote:
> > > > > > Move page_pool stats allocation in page_pool_create routine and get rid
> > > > > > of it for percpu page_pools.
> > > > > 
> > > > > Is there any reason why we do not need those kind stats for per cpu
> > > > > page_pool?
> > > > > 
> > > > 
> > > > IIRC discussing with Jakub, we decided to not support them since the pool is not
> > > > associated to any net_device in this case.
> > > 
> > > It seems what jakub suggested is to 'extend netlink to dump unbound page pools'?
> > 
> > I do not have a strong opinion about it (since we do not have any use-case for
> > it at the moment).
> > In the case we want to support stats for per-cpu page_pools, I think we should
> > not create a per-cpu recycle_stats pointer and add a page_pool_recycle_stats field
> > in page_pool struct since otherwise we will endup with ncpu^2 copies, right?
> > Do we want to support it now?
> > 
> > @Jakub, Jesper: what do you guys think?
> > 
> 
> 
> I do see an need for being able to access page_pool stats for all
> page_pool's in the system.
> And I do like Jakub's netlink based stats.

ack from my side if you have some use-cases in mind.
Some questions below:
- can we assume ethtool will be used to report stats just for 'global'
  page_pool (not per-cpu page_pool)?
- can we assume netlink/yaml will be used to report per-cpu page_pool stats?

I think in the current series we can fix the accounting part (in particular
avoiding memory wasting) and then we will figure out how to report percpu
page_pool stats through netlink/yaml. Agree?

Regards,
Lorenzo

> 
> --Jesper
> (p.s. I'm debugging some production issues with page_pool and broadcom
> bnxt_en driver).
> 

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