Re: [PATCH net-next v2 0/4] Implement classifier-action terse dump mode

From: Cong Wang <xiyou.wangcong@gmail.com>
To: Edward Cree <ecree@solarflare.com>
Cc: Vlad Buslov <vladbu@mellanox.com>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	Jiri Pirko <jiri@resnulli.us>,
	Davide Caratti <dcaratti@redhat.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
	Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH net-next v2 0/4] Implement classifier-action terse dump mode
Date: Mon, 18 May 2020 11:50:05 -0700	[thread overview]
Message-ID: <CAM_iQpWUzWyPZyDyVFLhOb5peVMp5Y4OeBxfSzuKY5bnF5Z02Q@mail.gmail.com> (raw)
In-Reply-To: <649b2756-1ddf-2b3e-cd13-1c577c50eaa2@solarflare.com>

On Mon, May 18, 2020 at 8:38 AM Edward Cree <ecree@solarflare.com> wrote:
>
> On 15/05/2020 12:40, Vlad Buslov wrote:
> > In order to
> > significantly improve filter dump rate this patch sets implement new
> > mode of TC filter dump operation named "terse dump" mode. In this mode
> > only parameters necessary to identify the filter (handle, action cookie,
> > etc.) and data that can change during filter lifecycle (filter flags,
> > action stats, etc.) are preserved in dump output while everything else
> > is omitted.
> I realise I'm a bit late, but isn't this the kind of policy that shouldn't
>  be hard-coded in the kernel?  I.e. if next year it turns out that some
>  user needs one parameter that's been omitted here, but not the whole dump,
>  are they going to want to add another mode to the uapi?
> Should this not instead have been done as a set of flags to specify which
>  pieces of information the caller wanted in the dump, rather than a mode
>  flag selecting a pre-defined set?

Excellent point!

I agree, this is more elegant, although potentially needs more work.

I am not sure whether we can simply pass those flags to cb->args[],
if not, that will need more work at netlink layer.

Thanks.