From: Daniel Colascione <dancol@google.com>
To: Jakub Kicinski <jakub.kicinski@netronome.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 17:50:15 -0700 [thread overview]
Message-ID: <CAKOZuev_fRPjH6PWRnDpWo0OjOo2EF+at_Uw4JXs25mwKoWF1A@mail.gmail.com> (raw)
In-Reply-To: <20180730174532.20010e0d@cakuba.netronome.com>
On Mon, Jul 30, 2018 at 5:45 PM, Jakub Kicinski
<jakub.kicinski@netronome.com> wrote:
> On Mon, 30 Jul 2018 17:33:39 -0700, Daniel Colascione wrote:
>> On Mon, Jul 30, 2018 at 5:26 PM, Jakub Kicinski wrote:
>> > 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.
>>
>> Sure. But such a thing doesn't exist right now (right?), and we can
>> add that more-efficient-in-that-one-case BPF interface when it lands.
>> I'd rather keep things simple for now.
>
> You mean map-in-map offload doesn't exist today? True, but it's on the
> roadmap for Netronome.
Sounds cool. I'd still wait until map-in-map offload lands until
adding the map-specific API though.
> Tangentially it would be really useful for us to have a "the map has
> actually been freed" notification/barrier. We have complaints of users
> creating huge maps and then trying to free and recreate them quickly,
> and the creation part failing with -ENOMEM, because the free from a
> workqueue didn't run, yet :( It'd probably require a different API to
> solve than what's discussed here, but since we're talking about syncing
> things I thought I'd put it out there...
Yeah. What you're talking about is what I meant upthread when I
briefly mentioned a "refcount draining approach" --- you'd block until
all references except your own to a map disappeared.
next prev parent reply other threads:[~2018-07-31 0:50 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
2018-07-31 0:33 ` Daniel Colascione
2018-07-31 0:45 ` Jakub Kicinski
2018-07-31 0:50 ` Daniel Colascione [this message]
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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