From: Jakub Kicinski <kuba@kernel.org>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Edward Cree <ecree@solarflare.com>,
netdev@vger.kernel.org, davem@davemloft.net,
netfilter-devel@vger.kernel.org, jiri@resnulli.us
Subject: Re: [RFC PATCH net] net: flow_offload: simplify hw stats check handling
Date: Thu, 7 May 2020 16:48:20 -0700 [thread overview]
Message-ID: <20200507164820.0f48c36b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20200507164643.GA10994@salvia>
On Thu, 7 May 2020 18:46:43 +0200 Pablo Neira Ayuso wrote:
> On Thu, May 07, 2020 at 04:49:15PM +0100, Edward Cree wrote:
> > On 07/05/2020 16:32, Pablo Neira Ayuso wrote:
> > > On Thu, May 07, 2020 at 03:59:09PM +0100, Edward Cree wrote:
> > >> Make FLOW_ACTION_HW_STATS_DONT_CARE be all bits, rather than none, so that
> > >> drivers and __flow_action_hw_stats_check can use simple bitwise checks.
> > >
> > > You have have to explain why this makes sense in terms of semantics.
> > >
> > > _DISABLED and _ANY are contradicting each other.
> > No, they aren't. The DISABLED bit means "I will accept disabled", it doesn't
> > mean "I insist on disabled". What _does_ mean "I insist on disabled" is if
> > the DISABLED bit is set and no other bits are.
> > So DISABLED | ANY means "I accept disabled; I also accept immediate or
> > delayed". A.k.a. "I don't care, do what you like".
>
> Jiri said Disabled means: bail out if you cannot disable it.
That's in TC uAPI Jiri chose... doesn't mean we have to do the same
internally.
> If the driver cannot disable, then it will have to check if the
> frontend is asking for Disabled (hence, report error to the frontend)
> or if it is actually asking for Don't care.
>
> What you propose is a context-based interpretation of the bits. So
> semantics depend on how you accumulate/combine bits.
>
> I really think bits semantics should be interpreted on the bit alone
> itself.
These 3 paragraphs sound to me like you were arguing for Ed's approach..
> There is one exception though, that is _ANY case, where you let the
> driver pick between delayed or immediate. But if the driver does not
> support for counters, it bails out in any case, so the outcome in both
> request is basically the same.
>
> You are asking for different outcome depending on how bits are
> combined, which can be done, but it sounds innecessarily complicated
> to me.
No, quite the opposite, the code as committed to net has magic values
which drivers have to check.
The counter-proposal is that each bit represents a configuration, and
if more than one bit is set the driver gets to choose which it prefers.
What could be simpler?
netfilter just has to explicitly set the field to DONT_CARE rather than
depending on 0 form zalloc() coinciding with the correct value.
next prev parent reply other threads:[~2020-05-07 23:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 14:59 [RFC PATCH net] net: flow_offload: simplify hw stats check handling Edward Cree
2020-05-07 15:32 ` Pablo Neira Ayuso
2020-05-07 15:49 ` Edward Cree
2020-05-07 16:46 ` Pablo Neira Ayuso
2020-05-07 23:48 ` Jakub Kicinski [this message]
2020-05-11 5:33 ` Jiri Pirko
2020-05-11 10:09 ` Edward Cree
2020-05-07 15:36 ` Pablo Neira Ayuso
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