From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: "Morten Brørup" <mb@smartsharesystems.com>,
"Mattias Rönnblom" <hofors@lysator.liu.se>,
"jackmin@nvidia.com" <jackmin@nvidia.com>,
"konstantin.v.ananyev@yandex.ru" <konstantin.v.ananyev@yandex.ru>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
Ruifeng Wang <Ruifeng.Wang@arm.com>,
Aditya Ambadipudi <Aditya.Ambadipudi@arm.com>,
Wathsala Wathawana Vithanage <wathsala.vithanage@arm.com>,
nd <nd@arm.com>, nd <nd@arm.com>
Subject: RE: [RFC] lib/st_ring: add single thread ring
Date: Sat, 26 Aug 2023 23:34:42 +0000 [thread overview]
Message-ID: <DBAPR08MB581461EC7AB0B39FD14F6DC898E2A@DBAPR08MB5814.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35D87B2D@smartserver.smartshare.dk>
<snip>
>
> > From: Mattias Rönnblom [mailto:hofors@lysator.liu.se]
> > Sent: Thursday, 24 August 2023 12.53
> >
> > On 2023-08-24 10:05, Morten Brørup wrote:
> > >> From: Honnappa Nagarahalli [mailto:Honnappa.Nagarahalli@arm.com]
> > >> Sent: Tuesday, 22 August 2023 07.47
> > >>
> > >>> From: Morten Brørup <mb@smartsharesystems.com>
> > >>> Sent: Monday, August 21, 2023 2:37 AM
> > >>>
> > >>>> From: Honnappa Nagarahalli
> [mailto:honnappa.nagarahalli@arm.com]
> > >>>> Sent: Monday, 21 August 2023 08.04
> > >>>>
> > >>>> Add a single thread safe and multi-thread unsafe ring data structure.
> > >>>> This library provides an simple and efficient alternative to
> > >>>> multi- thread safe ring when multi-thread safety is not required.
> > >>>>
> > >>>> Signed-off-by: Honnappa Nagarahalli
> > >>>> <honnappa.nagarahalli@arm.com>
> > >>>> ---
> > >>>
> > >>> Good idea.
> > >>>
> > >>> However, I prefer it to be implemented in the ring lib as one more
> > >>> ring
> > >> type.
> > >>> That would also give us a lot of the infrastructure (management
> > >>> functions, documentation and tests) for free.
> > >> IMO, the current code for rte_ring seems complex with C11 and
> > >> generic implementations, APIs for pointer objects vs APIs for
> > >> flexible element size etc. I did not want to introduce one more flavor and
> make it more complex.
> > >
> > > From the user perspective, I think one more ring flavor is less
> > > complex
> > than an entirely separate (very similar) library with its own set of
> > (very
> > similar) APIs.
> > >
> > > I agree that the ring lib has grown somewhat over-engineered, but
> > > please
> > don't use that as an argument for making the same-thread ring a separate
> lib.
> > >
> >
> > What's being proposed is a double-ended queue, not a ring (in the DPDK
> > sense).
> >
> > If you want to Swiss army knifify the rte_ring further and make it a
> > deque, then rte_stack should scrapped as well, since it's will become
> > just a subset of the new rte_ring_now_really_a_deque.
>
> OK. I accept that argument for not hacking it into the ring lib.
>
> Then I will suggest that the new "deque" library should be designed with
> multi-threading in mind, like its two sibling libs (ring and stack). This makes it
> easier to use, and leaves it open for expansion to other flavors in the future.
>
> It is perfectly acceptable that the first version only supports the same-thread
> deque flavor, and only the same-thread specialized APIs are exposed. I don't
> require any APIs or implementations supporting single-threaded (individual
> producer/consumer threads) or multi-threaded flavors, I only request that the
> design and API resemble those of its two sibling libraries. (And if there are no
> use cases for multi-threading flavors, they might never be added to this lib.)
+1, will aim for this
>
> >
> > > On the other hand: If the addition of an optimized same-thread ring
> > > flavor
> > would require too many invasive modifications of the existing ring
> > lib, I would accept that as an argument for not adding it as another
> > ring flavor to the existing ring lib.
> > >
> > >> The requirements are different as well. For ex: single thread ring
> > >> needs
> > APIs
> > >> for dequeuing and enqueuing at both ends of the ring which is not
> > applicable
> > >> to existing RTE ring.
> > >
> > > Yes, I will address this topic at the end of this mail.
> > >
> > >>
> > >> But, I see how the existing infra can be reused easily.
> > >
> > > This also goes for future infrastructure. I doubt that new
> > > infrastructure
> > added to the ring lib will also be added to the same-thread ring
> > lib... for reference, consider the PMDs containing copy-pasted code
> > from the mempool lib... none of the later improvements of the mempool
> > lib were implemented in those PMDs.
> > >
> > > In essence, I think this lib overlaps the existing ring lib too much
> > > to
> > justify making it a separate lib.
> > >
> > >>
> > >>>
> > >>> The ring lib already has performance-optimized APIs for
> > >>> single-consumer
> > and
> > >>> single-producer use, rte_ring_sc_dequeue_bulk() and
> > >>> rte_ring_sp_enqueue_burst(). Similar performance-optimized APIs
> > >>> for
> > single-
> > >>> thread use could be added: rte_ring_st_dequeue_bulk() and
> > >>> rte_ring_st_enqueue_burst().
> > >> Yes, the names look fine.
> > >> Looking through the code. We have the sync type enum:
> > >>
> > >> /** prod/cons sync types */
> > >> enum rte_ring_sync_type {
> > >> RTE_RING_SYNC_MT, /**< multi-thread safe (default mode) */
> > >> RTE_RING_SYNC_ST, /**< single thread only */
> > >> RTE_RING_SYNC_MT_RTS, /**< multi-thread relaxed tail sync */
> > >> RTE_RING_SYNC_MT_HTS, /**< multi-thread head/tail sync */
> > >> };
> > >>
> > >> The type RTE_RING_SYNC_ST needs better explanation (not a problem).
> > >> But,
> > this
> > >> name would have been ideal to use for single thread ring.
> > >> This enum does not need to be exposed to the users. However, there
> > >> are rte_ring_get_prod/cons_sync_type etc which seem to be exposed to
> the user.
> > >> This all means, we need to have a sync type name
> > >> RTE_RING_SYNC_MT_UNSAFE
> > (any
> > >> other better name?) which then affects API naming.
> > >> rte_ring_mt_unsafe_dequeue_bulk?
> > >
> > > As always, naming is difficult.
> > > The enum rte_ring_sync_type describes the producer and consumer
> > independently, whereas this ring type uses the same thread for both
> > producer and consumer.
> > > I think we should avoid MT in the names for this variant. How about:
> > >
> > > RTE_RING_SYNC_STPC /**< same thread for both producer and consumer
> > > */
> > >
> > > And:
> > >
> > > rte_ring_spc_dequeue_bulk() and rte_ring_spc_enqueue_burst()
> > >
> > >>
> > >>>
> > >>> Regardless if added to the ring lib or as a separate lib,
> > >>> "reverse" APIs
> > >> (for single-
> > >>> thread use only) and zero-copy APIs can be added at any time later.
> > >
> > > As the only current use case for "reverse" (i.e. dequeue at tail,
> > > enqueue at
> > head) APIs is for the same-thread ring flavor, we could start by
> > adding only the specialized variants of the "reverse" APIs,
> > rte_ring_spc_reverse_xxx(), and initially omit the generic
> > rte_ring_reverse_xxx() APIs. (We need better names; I used "reverse"
> > for explanation only.)
> > >
next prev parent reply other threads:[~2023-08-26 23:34 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-21 6:04 Honnappa Nagarahalli
2023-08-21 7:37 ` Morten Brørup
2023-08-22 5:47 ` Honnappa Nagarahalli
2023-08-24 8:05 ` Morten Brørup
2023-08-24 10:52 ` Mattias Rönnblom
2023-08-24 11:22 ` Morten Brørup
2023-08-26 23:34 ` Honnappa Nagarahalli [this message]
2023-08-21 21:14 ` Mattias Rönnblom
2023-08-22 5:43 ` Honnappa Nagarahalli
2023-08-22 8:04 ` Mattias Rönnblom
2023-08-22 16:28 ` Honnappa Nagarahalli
2023-09-04 10:13 ` Konstantin Ananyev
2023-09-04 18:10 ` Honnappa Nagarahalli
2023-09-05 8:19 ` Konstantin Ananyev
2024-04-01 1:37 ` [PATCH v1 0/2] deque: add multithread unsafe deque library Aditya Ambadipudi
2024-04-01 1:37 ` [PATCH v1 1/2] deque: add multi-thread unsafe double ended queue Aditya Ambadipudi
2024-04-06 9:35 ` Morten Brørup
2024-04-24 13:42 ` [PATCH v2 0/2] deque: add multithread unsafe deque library Aditya Ambadipudi
2024-04-24 13:42 ` [PATCH v2 1/2] deque: add multi-thread unsafe double ended queue Aditya Ambadipudi
2024-04-24 15:16 ` Morten Brørup
2024-04-24 17:21 ` Patrick Robb
2024-04-25 7:43 ` Ali Alnubani
2024-04-24 23:28 ` Mattias Rönnblom
2024-05-02 20:19 ` [PATCH v3 0/2] deque: add multithread unsafe deque library Aditya Ambadipudi
2024-05-02 20:19 ` [PATCH v3 1/2] deque: add multi-thread unsafe double ended queue Aditya Ambadipudi
2024-05-02 20:19 ` [PATCH v3 2/2] deque: add unit tests for the deque library Aditya Ambadipudi
2024-05-02 20:29 ` [PATCH v3 0/2] deque: add multithread unsafe " Aditya Ambadipudi
2024-04-24 13:42 ` [PATCH v2 2/2] deque: add unit tests for the " Aditya Ambadipudi
2024-04-01 1:37 ` [PATCH v1 " Aditya Ambadipudi
2024-04-01 14:05 ` [PATCH v1 0/2] deque: add multithread unsafe " Stephen Hemminger
2024-04-01 22:28 ` Aditya Ambadipudi
2024-04-02 0:05 ` Tyler Retzlaff
2024-04-02 0:47 ` Stephen Hemminger
2024-04-02 1:35 ` Honnappa Nagarahalli
2024-04-02 2:00 ` Stephen Hemminger
2024-04-02 2:14 ` Honnappa Nagarahalli
2024-04-02 2:53 ` Stephen Hemminger
[not found] ` <PAVPR08MB9185DC373708CBD16A38EFA8EF3E2@PAVPR08MB9185.eurprd08.prod.outlook.com>
2024-04-02 4:20 ` Tyler Retzlaff
2024-04-02 23:44 ` Stephen Hemminger
2024-04-03 0:12 ` Honnappa Nagarahalli
2024-04-03 23:52 ` Variable name issues with codespell Stephen Hemminger
2024-04-02 4:20 ` [PATCH v1 0/2] deque: add multithread unsafe deque library Tyler Retzlaff
2024-04-03 16:50 ` Honnappa Nagarahalli
2024-04-03 17:46 ` Tyler Retzlaff
2024-04-02 6:05 ` Mattias Rönnblom
2024-04-02 15:25 ` Stephen Hemminger
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