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From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: Daniel Colascione <dancol@google.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Joel Fernandes <joelaf@google.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Tim Murray <timmurray@google.com>,
	netdev <netdev@vger.kernel.org>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Lorenzo Colitti <lorenzo@google.com>,
	Chenbo Feng <fengc@google.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Alexei Starovoitov <ast@fb.com>
Subject: Re: [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command
Date: Mon, 30 Jul 2018 17:26:41 -0700	[thread overview]
Message-ID: <20180730172641.7d516231@cakuba.netronome.com> (raw)
In-Reply-To: <CAKOZuesH_LRdt15aXaRQRPSNzN-URTQWgSgr0zLsv8ZKFU9=9Q@mail.gmail.com>

On Mon, 30 Jul 2018 03:25:43 -0700, Daniel Colascione wrote:
> On Mon, Jul 30, 2018 at 3:04 AM, Daniel Borkmann <daniel@iogearbox.net> wrote:
> > Hmm, I don't think such UAPI as above is future-proof. In case we would want
> > a similar mechanism in future for other maps, we would need a whole new bpf
> > command or reuse BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES as a workaround though
> > the underlying map may not even be a map-to-map. Additionally, we don't have
> > any map object at hand in the above, so we couldn't make any finer grained
> > decisions either. Something like below would be more suitable and leaves room
> > for extending this further in future.  
> 
> YAGNI.  Your proposed mechanism doesn't add anything under the current
> implementation. 

FWIW in case of HW offload targeting a particular map may allow users
to avoid a potentially slow sync with all the devices on the system.

> It's also not clear how a map-specific synchronization
> command is supposed to work in cases where we swap multiple map
> references. Do we synchronize_rcu multiple times? Why would we impose
> that inefficiency just for the sake of some non-specific future
> extensibility? Add some kind of batching layer? The current approach
> works for the anticipated use cases.
> 
> While my preference is not to talk about map-to-maps at all in the
> user API and instead spec the thing as talking about map references in
> general, I'd rather have something that talks about
> references-to-maps-acquired-from-maps than this interface.

  reply	other threads:[~2018-07-31  0:26 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAKOZuesQ6GdNTGDFsNi4o8LYzxLBtYZ=Cz4=aZbqqCNia+QFnQ@mail.gmail.com>
2018-07-29 20:58 ` [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command Daniel Colascione
2018-07-30 10:04   ` Daniel Borkmann
2018-07-30 10:25     ` Daniel Colascione
2018-07-31  0:26       ` Jakub Kicinski [this message]
2018-07-31  0:33         ` Daniel Colascione
2018-07-31  0:45           ` Jakub Kicinski
2018-07-31  0:50             ` Daniel Colascione
2018-07-31  1:14               ` Jakub Kicinski
2018-07-31  8:34           ` Daniel Borkmann
2018-07-31  9:36             ` Daniel Colascione
2018-08-10 22:52               ` Alexei Starovoitov
2018-08-14 20:37                 ` Daniel Colascione
2018-08-16  4:01                   ` Alexei Starovoitov
2018-10-12 10:54                     ` [PATCH v4] Wait for running BPF programs when updating map-in-map Daniel Colascione
2018-10-12 20:54                       ` Joel Fernandes
2018-10-13  2:31                       ` Alexei Starovoitov
2018-10-16 17:39                         ` Joel Fernandes
2018-10-18 15:46                           ` Alexei Starovoitov
2018-10-18 23:36                             ` Joel Fernandes
2018-11-10  2:01                               ` Chenbo Feng
2018-11-10 15:22                                 ` Greg KH
2018-11-10 18:58                                   ` Chenbo Feng
     [not found]   ` <CAKOZues6SE_c=ix7ap6QaJHqd1TmYpWWMJiu3=TtuqgKuqOUCA@mail.gmail.com>
2018-08-10 22:29     ` [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command Alexei Starovoitov

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