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From: "Eads, Gage" <gage.eads@intel.com>
To: Ola Liljedahl <Ola.Liljedahl@arm.com>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>
Cc: "jerinj@marvell.com" <jerinj@marvell.com>,
	"mczekaj@marvell.com" <mczekaj@marvell.com>, nd <nd@arm.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"arybchenko@solarflare.com" <arybchenko@solarflare.com>
Subject: Re: [dpdk-dev] [PATCH v7 0/6] Add lock-free ring and mempool handler
Date: Thu, 4 Apr 2019 22:28:07 +0000	[thread overview]
Message-ID: <9184057F7FC11744A2107296B6B8EB1E5421151D@FMSMSX108.amr.corp.intel.com> (raw)
Message-ID: <20190404222807.Cb-gApDrci3qPG-UvANtrR-vYv_mqVXYJVEsVqbxa28@z> (raw)
In-Reply-To: <1554200290.11194.8.camel@arm.com>

> On Mon, 2019-04-01 at 19:23 +0000, Eads, Gage wrote:
> > >
> > >
> > > On Mon, 18 Mar 2019 21:49:44 +0000
> > > "Eads, Gage" <gage.eads@intel.com> wrote:
> > >
> > > >
> > > > Hi all,
> > > >
> > > > Friendly reminder that in order to get this feature into 19.08
> > > > (assuming
> > > folks also want that :)), the API deprecation notice needs to be
> > > merged into 19.05.
> > > >
> > > >
> > > > Thanks,
> > > > Gage
> > > Given the recent API/ABI stability discussion, this is the kind of
> > > patch that really needs to be examined and justified.
> > Can you point me to the discussion (assuming it was on the ML)? I'm
> > aware of Ferruh's changes to the docs, but not the discussion you
> referenced.
> >
> > The lock-free ring functionality itself is a valuable addition to
> > DPDK, primarily because it lacks the standard ring's non-preemptive
> > constraint. The non-preemptive constraint is important in an
> > application with both high priority, performance-sensitive data-plane
> > components and low-priority control-plane components. This was
> > important enough to warrant further clarification recently[1], and has
> > been a discussion topic for some time[2][3].
> >
> > The modified API, rte_ring_get_memsize(), was added to allow users to
> > initialize rings in separately allocated memory. This function isn't
> > called in DPDK's examples/apps/drivers, and a quick google search
> > didn't turn up any open source projects that call the function, so I
> > suspect that a majority of ring code uses rte_ring_create() instead of
> > rte_ring_get_memsize() + rte_ring_init(). So I suspect this interface
> > change will affect a small percentage of DPDK users.
> >
> > As a straw-man counter-proposal, we could instead introduce a
> > lock-free specific function rte_lf_ring_get_memsize() that lock-free
> > ring users would call instead of rte_ring_get_memsize(). This would
> > avoid the API modification,
> > but:
> > - It's awkward to have one rte_lf_ring_* function and otherwise access
> > the lock-free ring through rte_ring_* functions.
> > - It's also easy to envision a user incorrectly calling
> > rte_ring_get_memsize() rather than rte_lf_ring_get_memsize() for a
> > lock-free ring, since otherwise
> > rte_ring_* functions are used. DPDK would have no way to detect that
> > the allocated memory is too small, and if such a bug occurs it would
> > manifest itself as memory corruption.
> > - Changing rte_ring_get_memsize() to take a flags argument may be the
> > better long-term design, if another flag is introduced that likewise
> > uses a different ring size.
> >
> > Another approach is to break out the lock-free ring into a fully separate
> API.
> As in the RFC I posted: http://patches.dpdk.org/patch/50095/
> Cleaner API, simpler implementation.
> 
> >  One of the goals of my patchset was to allow applications to switch to lock-
> > free rings with minimal code change; I think the value of the lock-free ring
> > warrants such an approach.
> 
> A noble goal but personally I think DPDK API's and implementations are
> getting more and more messy and thus difficult to use and difficult to
> maintain.
> Is it so much worse to have separate but structurally equivalent API's?

No -- I think both are valid options, with their own tradeoffs.

> Yes, blocking vs non-blocking can no longer be selected at runtime (startup
> time), I think this is the biggest limitation.

Run-time selection with the LF flag means we can easily re-use a large amount of pre-existing ring code -- e.g. the way the ring tests are re-purposed for lock-free rings in this patchset.

The implementation may not be as easily maintained, but we don't have to maintain LF-specific tests/benchmarks/etc.

Maintainers/tech leads, do y'all have a preference?

Thanks,
Gage

  parent reply	other threads:[~2019-04-04 22:28 UTC|newest]

Thread overview: 123+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-10 21:01 [dpdk-dev] [PATCH 0/6] Add non-blocking ring Gage Eads
2019-01-10 21:01 ` [dpdk-dev] [PATCH 1/6] ring: change head and tail to pointer-width size Gage Eads
2019-01-11  4:38   ` Stephen Hemminger
2019-01-11 19:07     ` Eads, Gage
2019-01-11 10:25   ` Burakov, Anatoly
2019-01-11 19:12     ` Eads, Gage
2019-01-11 19:55       ` Stephen Hemminger
2019-01-15 15:48         ` Eads, Gage
2019-01-11 10:40   ` Burakov, Anatoly
2019-01-11 10:58     ` Bruce Richardson
2019-01-11 11:30       ` Burakov, Anatoly
     [not found]         ` <20190111115851.GC3336@bricha3-MOBL.ger.corp.intel.com>
2019-01-11 19:27           ` Eads, Gage
2019-01-21 14:14             ` Burakov, Anatoly
2019-01-22 18:27               ` Eads, Gage
2019-01-10 21:01 ` [dpdk-dev] [PATCH 2/6] ring: add a non-blocking implementation Gage Eads
2019-01-10 21:01 ` [dpdk-dev] [PATCH 3/6] test_ring: add non-blocking ring autotest Gage Eads
2019-01-10 21:01 ` [dpdk-dev] [PATCH 4/6] test_ring_perf: add non-blocking ring perf test Gage Eads
2019-01-10 21:01 ` [dpdk-dev] [PATCH 5/6] mempool/ring: add non-blocking ring handlers Gage Eads
2019-01-13 13:43   ` Andrew Rybchenko
2019-01-10 21:01 ` [dpdk-dev] [PATCH 6/6] doc: add NB ring comment to EAL "known issues" Gage Eads
2019-01-11  2:51   ` Varghese, Vipin
2019-01-11 19:30     ` Eads, Gage
2019-01-14  0:07       ` Varghese, Vipin
2019-01-15 23:52 ` [dpdk-dev] [PATCH v2 0/5] Add non-blocking ring Gage Eads
2019-01-15 23:52   ` [dpdk-dev] [PATCH v2 1/5] ring: change head and tail to pointer-width size Gage Eads
2019-01-15 23:52   ` [dpdk-dev] [PATCH v2 2/5] ring: add a non-blocking implementation Gage Eads
2019-01-15 23:52   ` [dpdk-dev] [PATCH v2 3/5] test_ring: add non-blocking ring autotest Gage Eads
2019-01-15 23:52   ` [dpdk-dev] [PATCH v2 4/5] test_ring_perf: add non-blocking ring perf test Gage Eads
2019-01-15 23:52   ` [dpdk-dev] [PATCH v2 5/5] mempool/ring: add non-blocking ring handlers Gage Eads
2019-01-16  0:26   ` [dpdk-dev] [PATCH v2 0/5] Add non-blocking ring Stephen Hemminger
2019-01-18 15:23   ` [dpdk-dev] [PATCH v3 " Gage Eads
2019-01-18 15:23     ` [dpdk-dev] [PATCH v3 1/5] ring: add 64-bit headtail structure Gage Eads
2019-01-18 15:23     ` [dpdk-dev] [PATCH v3 2/5] ring: add a non-blocking implementation Gage Eads
2019-01-22 10:12       ` Ola Liljedahl
2019-01-22 14:49       ` Ola Liljedahl
2019-01-22 21:31         ` Eads, Gage
2019-01-23 10:16           ` Ola Liljedahl
2019-01-25 17:21             ` Eads, Gage
2019-01-28 10:35               ` Ola Liljedahl
2019-01-28 18:54                 ` Eads, Gage
2019-01-28 22:31                   ` Ola Liljedahl
2019-01-28 13:34               ` Jerin Jacob Kollanukkaran
2019-01-28 13:43                 ` Ola Liljedahl
2019-01-28 14:04                   ` Jerin Jacob Kollanukkaran
2019-01-28 14:06                     ` Ola Liljedahl
2019-01-28 18:59                 ` Eads, Gage
2019-01-18 15:23     ` [dpdk-dev] [PATCH v3 3/5] test_ring: add non-blocking ring autotest Gage Eads
2019-01-18 15:23     ` [dpdk-dev] [PATCH v3 4/5] test_ring_perf: add non-blocking ring perf test Gage Eads
2019-01-18 15:23     ` [dpdk-dev] [PATCH v3 5/5] mempool/ring: add non-blocking ring handlers Gage Eads
2019-01-22  9:27     ` [dpdk-dev] [PATCH v3 0/5] Add non-blocking ring Ola Liljedahl
2019-01-22 10:15       ` Ola Liljedahl
2019-01-22 19:15       ` Eads, Gage
2019-01-23 16:02       ` Jerin Jacob Kollanukkaran
2019-01-23 16:29         ` Ola Liljedahl
2019-01-28 13:10           ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-01-25  5:20     ` [dpdk-dev] " Honnappa Nagarahalli
2019-01-25 17:42       ` Eads, Gage
2019-01-25 17:56       ` Eads, Gage
2019-01-28 10:41         ` Ola Liljedahl
2019-01-28 18:14     ` [dpdk-dev] [PATCH v4 " Gage Eads
2019-01-28 18:14       ` [dpdk-dev] [PATCH v4 1/5] ring: add 64-bit headtail structure Gage Eads
2019-01-29 12:56         ` Ola Liljedahl
2019-01-30  4:26           ` Eads, Gage
2019-01-28 18:14       ` [dpdk-dev] [PATCH v4 2/5] ring: add a non-blocking implementation Gage Eads
2019-01-28 18:14       ` [dpdk-dev] [PATCH v4 3/5] test_ring: add non-blocking ring autotest Gage Eads
2019-01-28 18:14       ` [dpdk-dev] [PATCH v4 4/5] test_ring_perf: add non-blocking ring perf test Gage Eads
2019-01-28 18:14       ` [dpdk-dev] [PATCH v4 5/5] mempool/ring: add non-blocking ring handlers Gage Eads
2019-03-05 17:40       ` [dpdk-dev] [PATCH v5 0/6] Add lock-free ring and mempool handler Gage Eads
2019-03-05 17:40         ` [dpdk-dev] [PATCH v5 1/6] ring: add a pointer-width headtail structure Gage Eads
2019-03-05 17:40         ` [dpdk-dev] [PATCH v5 2/6] ring: add a ring start marker Gage Eads
2019-03-05 17:40         ` [dpdk-dev] [PATCH v5 3/6] ring: add a lock-free implementation Gage Eads
2019-03-05 17:40         ` [dpdk-dev] [PATCH v5 4/6] test_ring: add lock-free ring autotest Gage Eads
2019-03-05 17:40         ` [dpdk-dev] [PATCH v5 5/6] test_ring_perf: add lock-free ring perf test Gage Eads
2019-03-05 17:40         ` [dpdk-dev] [PATCH v5 6/6] mempool/ring: add lock-free ring handlers Gage Eads
2019-03-06 15:03         ` [dpdk-dev] [PATCH v6 0/6] Add lock-free ring and mempool handler Gage Eads
2019-03-06 15:03           ` [dpdk-dev] [PATCH v6 1/6] ring: add a pointer-width headtail structure Gage Eads
2019-03-06 15:03           ` [dpdk-dev] [PATCH v6 2/6] ring: add a ring start marker Gage Eads
2019-03-06 15:03           ` [dpdk-dev] [PATCH v6 3/6] ring: add a lock-free implementation Gage Eads
2019-03-06 15:03           ` [dpdk-dev] [PATCH v6 4/6] test_ring: add lock-free ring autotest Gage Eads
2019-03-06 15:03           ` [dpdk-dev] [PATCH v6 5/6] test_ring_perf: add lock-free ring perf test Gage Eads
2019-03-06 15:03           ` [dpdk-dev] [PATCH v6 6/6] mempool/ring: add lock-free ring handlers Gage Eads
2019-03-18 21:35           ` [dpdk-dev] [PATCH v7 0/6] Add lock-free ring and mempool handler Gage Eads
2019-03-18 21:35             ` Gage Eads
2019-03-18 21:35             ` [dpdk-dev] [PATCH v7 1/6] ring: add a pointer-width headtail structure Gage Eads
2019-03-18 21:35               ` Gage Eads
2019-03-18 21:35             ` [dpdk-dev] [PATCH v7 2/6] ring: add a ring start marker Gage Eads
2019-03-18 21:35               ` Gage Eads
2019-03-18 21:35             ` [dpdk-dev] [PATCH v7 3/6] ring: add a lock-free implementation Gage Eads
2019-03-18 21:35               ` Gage Eads
2019-03-19 15:50               ` Stephen Hemminger
2019-03-19 15:50                 ` Stephen Hemminger
2019-03-18 21:35             ` [dpdk-dev] [PATCH v7 4/6] test_ring: add lock-free ring autotest Gage Eads
2019-03-18 21:35               ` Gage Eads
2019-03-18 21:35             ` [dpdk-dev] [PATCH v7 5/6] test_ring_perf: add lock-free ring perf test Gage Eads
2019-03-18 21:35               ` Gage Eads
2019-03-18 21:35             ` [dpdk-dev] [PATCH v7 6/6] mempool/ring: add lock-free ring handlers Gage Eads
2019-03-18 21:35               ` Gage Eads
2019-03-18 21:49             ` [dpdk-dev] [PATCH v7 0/6] Add lock-free ring and mempool handler Eads, Gage
2019-03-18 21:49               ` Eads, Gage
2019-03-19 15:51               ` Stephen Hemminger
2019-03-19 15:51                 ` Stephen Hemminger
2019-04-01 19:23                 ` Eads, Gage
2019-04-01 19:23                   ` Eads, Gage
2019-04-02 10:16                   ` Ola Liljedahl
2019-04-02 10:16                     ` Ola Liljedahl
2019-04-04 22:28                     ` Eads, Gage [this message]
2019-04-04 22:28                       ` Eads, Gage
2019-03-19  1:20             ` [dpdk-dev] [PATCH v8 " Gage Eads
2019-03-19  1:20               ` Gage Eads
2019-03-19  1:20               ` [dpdk-dev] [PATCH v8 1/6] ring: add a pointer-width headtail structure Gage Eads
2019-03-19  1:20                 ` Gage Eads
2019-03-19  1:20               ` [dpdk-dev] [PATCH v8 2/6] ring: add a ring start marker Gage Eads
2019-03-19  1:20                 ` Gage Eads
2019-03-19  1:20               ` [dpdk-dev] [PATCH v8 3/6] ring: add a lock-free implementation Gage Eads
2019-03-19  1:20                 ` Gage Eads
2019-03-19  1:20               ` [dpdk-dev] [PATCH v8 4/6] test_ring: add lock-free ring autotest Gage Eads
2019-03-19  1:20                 ` Gage Eads
2019-03-19  1:20               ` [dpdk-dev] [PATCH v8 5/6] test_ring_perf: add lock-free ring perf test Gage Eads
2019-03-19  1:20                 ` Gage Eads
2019-03-19  1:20               ` [dpdk-dev] [PATCH v8 6/6] mempool/ring: add lock-free ring handlers Gage Eads
2019-03-19  1:20                 ` Gage Eads
2019-04-03 16:46               ` [dpdk-dev] [PATCH v8 0/6] Add lock-free ring and mempool handler Thomas Monjalon
2019-04-03 16:46                 ` Thomas Monjalon

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