netdev - Re: [PATCH v3 net-next 01/23] lib: add reference counting tracking infrastructure

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Message-ID: <20211208065943.61b6220b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 8 Dec 2021 06:59:43 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Andrzej Hajda <andrzej.hajda@...el.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>, Greg KH <greg@...ah.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 net-next 01/23] lib: add reference counting tracking
 infrastructure

On Wed, 8 Dec 2021 15:09:17 +0100 Andrzej Hajda wrote:
> On 05.12.2021 05:21, Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@...gle.com>
> >
> > It can be hard to track where references are taken and released.
> >
> > In networking, we have annoying issues at device or netns dismantles,
> > and we had various proposals to ease root causing them.
> >
> > This patch adds new infrastructure pairing refcount increases
> > and decreases. This will self document code, because programmers
> > will have to associate increments/decrements.
> >
> > This is controled by CONFIG_REF_TRACKER which can be selected
> > by users of this feature.
> >
> > This adds both cpu and memory costs, and thus should probably be
> > used with care.
> >
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
> 
> Life is surprising, I was working on my own framework, solving the same 
> issue, with intention to publish it in few days :)
>
> My approach was little different:
> 
> 1. Instead of creating separate framework I have extended debug_objects.
> 
> 2. There were no additional fields in refcounted object and trackers - 
> infrastructure of debug_objects was reused - debug_objects tracked both 
> pointers of refcounted object and its users.
> 
> 
> Have you considered using debug_object? it seems to be good place to put 
> it there, I am not sure about performance differences.

Something along these lines?

https://lore.kernel.org/all/20211117174723.2305681-1-kuba@kernel.org/

;)

> One more thing about design - as I understand CONFIG_REF_TRACKER turns 
> on all trackers in whole kernel, have you considered possibility/helpers 
> to enable/disable tracking per class of objects?