netdev - Re: [PATCH net-next v3 00/13] net: page_pool: add netlink-based introspection

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Date: Sat, 25 Nov 2023 20:57:24 +0000
From: Shakeel Butt <shakeelb@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com, 
	pabeni@...hat.com, almasrymina@...gle.com, hawk@...nel.org, 
	ilias.apalodimas@...aro.org, dsahern@...il.com, dtatulea@...dia.com, 
	willemb@...gle.com
Subject: Re: [PATCH net-next v3 00/13] net: page_pool: add netlink-based introspection

On Tue, Nov 21, 2023 at 07:44:07PM -0800, Jakub Kicinski wrote:
> We recently started to deploy newer kernels / drivers at Meta,
> making significant use of page pools for the first time.
> We immediately run into page pool leaks both real and false positive
> warnings. As Eric pointed out/predicted there's no guarantee that
> applications will read / close their sockets so a page pool page
> may be stuck in a socket (but not leaked) forever. This happens
> a lot in our fleet. Most of these are obviously due to application
> bugs but we should not be printing kernel warnings due to minor
> application resource leaks.
> 
> Conversely the page pool memory may get leaked at runtime, and
> we have no way to detect / track that, unless someone reconfigures
> the NIC and destroys the page pools which leaked the pages.
> 
> The solution presented here is to expose the memory use of page
> pools via netlink. This allows for continuous monitoring of memory
> used by page pools, regardless if they were destroyed or not.
> Sample in patch 15 can print the memory use and recycling
> efficiency:
> 
> $ ./page-pool
>     eth0[2]	page pools: 10 (zombies: 0)
> 		refs: 41984 bytes: 171966464 (refs: 0 bytes: 0)
> 		recycling: 90.3% (alloc: 656:397681 recycle: 89652:270201)

Hi Jakub, I am wondering if you considered to expose these metrics
through meminfo/vmstat as well, is that a bad idea or is this/netlink
more of a preference?

thanks,
Shakeel