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From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: "Ruifeng Wang (Arm Technology China)" <Ruifeng.Wang@arm.com>,
	"bruce.richardson@intel.com" <bruce.richardson@intel.com>,
	"vladimir.medvedkin@intel.com" <vladimir.medvedkin@intel.com>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	"konstantin.ananyev@intel.com" <konstantin.ananyev@intel.com>,
	"Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>,
	Dharmik Thakkar <Dharmik.Thakkar@arm.com>, nd <nd@arm.com>,
	"paulmck@linux.ibm.com" <paulmck@linux.ibm.com>, nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2 1/6] doc/rcu: add RCU integration design details
Date: Fri, 6 Sep 2019 19:44:20 +0000
Message-ID: <VE1PR08MB5149FD6FCB864FF80F6301F998BA0@VE1PR08MB5149.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <20190906094534.36060-2-ruifeng.wang@arm.com>

Adding Paul for feedback on design

> -----Original Message-----
> From: Ruifeng Wang <ruifeng.wang@arm.com>
> Sent: Friday, September 6, 2019 4:45 AM
> To: bruce.richardson@intel.com; vladimir.medvedkin@intel.com;
> olivier.matz@6wind.com
> Cc: dev@dpdk.org; stephen@networkplumber.org;
> konstantin.ananyev@intel.com; Gavin Hu (Arm Technology China)
> <Gavin.Hu@arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Dharmik Thakkar
> <Dharmik.Thakkar@arm.com>; nd <nd@arm.com>
> Subject: [PATCH v2 1/6] doc/rcu: add RCU integration design details
> 
> From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> 
> Add a section to describe a design to integrate QSBR RCU library with other
> libraries in DPDK.
> 
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> ---
>  doc/guides/prog_guide/rcu_lib.rst | 52 +++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/rcu_lib.rst
> b/doc/guides/prog_guide/rcu_lib.rst
> index 8fe5b1f73..211948530 100644
> --- a/doc/guides/prog_guide/rcu_lib.rst
> +++ b/doc/guides/prog_guide/rcu_lib.rst
> @@ -186,3 +186,55 @@ However, when
> ``CONFIG_RTE_LIBRTE_RCU_DEBUG`` is enabled, these APIs aid  in debugging
> issues. One can mark the access to shared data structures on the  reader side
> using these APIs. The ``rte_rcu_qsbr_quiescent()`` will check if  all the locks are
> unlocked.
> +
> +Integrating QSBR RCU with other libraries
> +-----------------------------------------
> +
> +Lock-free algorithms place additional burden on the application to
> +reclaim memory. Integrating memory reclamation mechanisms in the
> +libraries help remove some of the burden. Though QSBR method presents
> +flexibility to achieve performance, it presents challenges while integrating
> with libraries.
> +
> +The memory reclamation process using QSBR can be split into 4 parts:
> +
> +#. Initialization
> +#. Quiescent State Reporting
> +#. Reclaiming Resources
> +#. Shutdown
> +
> +The design proposed here assigns different parts of this process to client
> libraries and applications. The term 'client library' refers to data structure
> libraries such at rte_hash, rte_lpm etc. in DPDK or similar libraries outside of
> DPDK. The term 'application' refers to the packet processing application that
> makes use of DPDK such as L3 Forwarding example application, OVS, VPP etc..
> +
> +The application has to handle 'Initialization' and 'Quiescent State
> +Reporting'. So,
> +
> +* the application has to create the RCU variable and register the reader
> threads to report their quiescent state.
> +* the application has to register the same RCU variable with the client library.
> +* reader threads in the application have to report the quiescent state. This
> allows for the application to control the length of the critical section/how
> frequently the application wants to report the quiescent state.
> +
> +The client library will handle 'Reclaiming Resources' part of the
> +process. The client libraries will make use of the writer thread
> +context to execute the memory reclamation algorithm. So,
> +
> +* client library should provide an API to register a RCU variable that it will use.
> +* client library should trigger the readers to report quiescent state status
> upon deleting the resources by calling ``rte_rcu_qsbr_start``.
> +
> +* client library should store the token and deleted resources for later use to
> free them after the readers have reported their quiescent state. Since the
> readers will report the quiescent state status in the order of deletion, the
> library must store the tokens/resources in the order in which the resources
> were deleted. A FIFO data structure would achieve the desired results. The
> length of the FIFO would depend on the rate of deletion and the rate at which
> the readers report their quiescent state. In the worst case the length of FIFO
> would be equal to the maximum number of resources the data structure
> supports. However, in most cases, the length will be much smaller. But, the
> client library should not take the length of FIFO as an input from the
> application. Instead, it should implement a data structure which should be able
> to grow/shrink dynamically. Overhead introduced by such a data structure on
> delete operations should be considered as well.
> +
> +* client library should query the quiescent state and free the resources. It
> should make use of non-blocking ``rte_rcu_qsbr_check`` API to query the
> quiescent state. This allows the application to do useful work while the readers
> report their quiescent state. If there are tokens/resources present in the FIFO
> already, the delete API should peek the head of the FIFO and check the
> quiescent state status. If the status is success, the token/resource should be
> dequeued and the resource should be freed. This process can be repeated till
> the quiescent state status for a token returns failure indicating that
> subsequent tokens will also fail quiescent state status query. The same process
> can be incorporated while adding new entries in the data structure if the client
> library runs out of resources.
> +
> +The 'Shutdown' process needs to be shared between the application and
> +the client library.
> +
> +* the application should make sure that the reader threads are not using the
> shared data structure, unregister the reader threads from the QSBR variable
> before calling the client library's shutdown function.
> +
> +* client library should check the quiescent state status of all the tokens that
> may be present in the FIFO and free the resources. It should make use of non-
> blocking ``rte_rcu_qsbr_check`` API to query the quiescent state. If any of the
> tokens do not pass the quiescent state check, the client library should print an
> error and stop the memory reclamation process.
> +
> +Integrating the resource reclamation with client libraries removes the
> +burden from the application and makes it easy to use lock-free algorithms.
> +
> +This design has several advantages over currently known methods.
> +
> +#. Application does not need a dedicated thread to reclaim resources.
> Memory
> +   reclamation happens as part of the writer thread with little impact on
> +   performance.
> +#. The client library has better control over the resources. For ex: the client
> +   library can attempt to reclaim when it has run out of resources.
> --
> 2.17.1


  reply	other threads:[~2019-09-06 19:44 UTC|newest]

Thread overview: 137+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-22  6:34 [dpdk-dev] [RFC PATCH 0/3] RCU integration with LPM library Ruifeng Wang
2019-08-22  6:34 ` [dpdk-dev] [RFC PATCH 1/3] doc/rcu: add RCU integration design details Ruifeng Wang
2019-08-22  6:34 ` [dpdk-dev] [RFC PATCH 2/3] lib/ring: add peek API Ruifeng Wang
2019-08-22  6:34 ` [dpdk-dev] [RFC PATCH 3/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2019-08-23  1:23   ` Stephen Hemminger
2019-08-26  3:11     ` Ruifeng Wang (Arm Technology China)
2019-08-26  5:32       ` Honnappa Nagarahalli
2019-08-22 15:52 ` [dpdk-dev] [RFC PATCH 0/3] RCU integration with LPM library Honnappa Nagarahalli
2019-09-06  9:45 ` [dpdk-dev] [PATCH v2 0/6] " Ruifeng Wang
2019-09-06  9:45   ` [dpdk-dev] [PATCH v2 1/6] doc/rcu: add RCU integration design details Ruifeng Wang
2019-09-06 19:44     ` Honnappa Nagarahalli [this message]
2019-09-06  9:45   ` [dpdk-dev] [PATCH v2 2/6] lib/ring: add peek API Ruifeng Wang
2019-09-06  9:45   ` [dpdk-dev] [PATCH v2 3/6] lib/lpm: integrate RCU QSBR Ruifeng Wang
2019-09-06 19:44     ` Honnappa Nagarahalli
2019-09-18 16:15     ` Medvedkin, Vladimir
2019-09-19  6:17       ` Ruifeng Wang (Arm Technology China)
2019-09-06  9:45   ` [dpdk-dev] [PATCH v2 4/6] app/test: add test case for LPM RCU integration Ruifeng Wang
2019-09-06 19:45     ` Honnappa Nagarahalli
2019-09-06  9:45   ` [dpdk-dev] [PATCH v2 5/6] test/lpm: reset total time Ruifeng Wang
2019-09-18 16:17     ` Medvedkin, Vladimir
2019-09-19  6:22       ` Ruifeng Wang (Arm Technology China)
2019-09-06  9:45   ` [dpdk-dev] [PATCH v2 6/6] test/lpm: add RCU integration performance tests Ruifeng Wang
2019-09-06 19:46     ` Honnappa Nagarahalli
2019-10-01  6:29   ` [dpdk-dev] [PATCH v3 0/3] Add RCU reclamation APIs Honnappa Nagarahalli
2019-10-01  6:29     ` [dpdk-dev] [PATCH v3 1/3] lib/ring: add peek API Honnappa Nagarahalli
2019-10-02 18:42       ` Ananyev, Konstantin
2019-10-03 19:49         ` Honnappa Nagarahalli
2019-10-07  9:01           ` Ananyev, Konstantin
2019-10-09  4:25             ` Honnappa Nagarahalli
2019-10-10 15:09               ` Ananyev, Konstantin
2019-10-11  5:03                 ` Honnappa Nagarahalli
2019-10-11 14:41                   ` Ananyev, Konstantin
2019-10-11 18:28                     ` Honnappa Nagarahalli
2019-10-13 20:09                       ` Ananyev, Konstantin
2019-10-14  4:11                         ` Honnappa Nagarahalli
2019-10-01  6:29     ` [dpdk-dev] [PATCH v3 2/3] lib/rcu: add resource reclamation APIs Honnappa Nagarahalli
2019-10-02 17:39       ` Ananyev, Konstantin
2019-10-03  6:29         ` Honnappa Nagarahalli
2019-10-03 12:26           ` Ananyev, Konstantin
2019-10-04  6:07             ` Honnappa Nagarahalli
2019-10-07 10:46               ` Ananyev, Konstantin
2019-10-13  4:35                 ` Honnappa Nagarahalli
2019-10-02 18:50       ` Ananyev, Konstantin
2019-10-03  6:42         ` Honnappa Nagarahalli
2019-10-03 11:52           ` Ananyev, Konstantin
2019-10-04 19:01       ` Medvedkin, Vladimir
2019-10-07 13:11       ` Medvedkin, Vladimir
2019-10-13  3:02         ` Honnappa Nagarahalli
2019-10-15 16:48           ` Medvedkin, Vladimir
2019-10-18  3:47             ` Honnappa Nagarahalli
2019-10-01  6:29     ` [dpdk-dev] [PATCH v3 3/3] doc/rcu: add RCU integration design details Honnappa Nagarahalli
2020-03-29 20:57     ` [dpdk-dev] [PATCH v3 0/3] Add RCU reclamation APIs Thomas Monjalon
2020-03-30 17:37       ` Honnappa Nagarahalli
2020-04-03 18:41     ` [dpdk-dev] [PATCH v4 0/4] " Honnappa Nagarahalli
2020-04-03 18:41       ` [dpdk-dev] [PATCH v4 1/4] lib/rcu: add resource " Honnappa Nagarahalli
2020-04-07 17:39         ` Ananyev, Konstantin
2020-04-19 23:22           ` Honnappa Nagarahalli
2020-04-20  8:19             ` Ananyev, Konstantin
2020-04-03 18:41       ` [dpdk-dev] [PATCH v4 2/4] test/rcu: test cases for RCU defer queue APIs Honnappa Nagarahalli
2020-04-03 18:41       ` [dpdk-dev] [PATCH v4 3/4] doc/rcu: add RCU integration design details Honnappa Nagarahalli
2020-04-03 18:41       ` [dpdk-dev] [PATCH v4 4/4] lib/rcu: add additional debug logs Honnappa Nagarahalli
2020-04-22  3:30     ` [dpdk-dev] [PATCH v5 0/4] Add RCU reclamation APIs Honnappa Nagarahalli
2020-04-22  3:30       ` [dpdk-dev] [PATCH v5 1/4] lib/rcu: add resource " Honnappa Nagarahalli
2020-04-22  8:36         ` Ananyev, Konstantin
2020-04-22  8:42           ` David Marchand
2020-04-22  8:51             ` David Marchand
2020-04-22  9:26               ` Ananyev, Konstantin
2020-04-22  3:30       ` [dpdk-dev] [PATCH v5 2/4] test/rcu: test cases for RCU defer queue APIs Honnappa Nagarahalli
2020-04-22  8:27         ` Ananyev, Konstantin
2020-04-22  3:30       ` [dpdk-dev] [PATCH v5 3/4] doc/rcu: add RCU integration design details Honnappa Nagarahalli
2020-04-22  3:30       ` [dpdk-dev] [PATCH v5 4/4] lib/rcu: add additional debug logs Honnappa Nagarahalli
2020-04-22  8:25         ` Ananyev, Konstantin
2020-04-22 18:46       ` [dpdk-dev] [PATCH v5 0/4] Add RCU reclamation APIs David Marchand
2019-10-01 18:28   ` [dpdk-dev] [PATCH v3 0/3] RCU integration with LPM library Honnappa Nagarahalli
2019-10-01 18:28     ` [dpdk-dev] [PATCH v3 1/3] lib/lpm: integrate RCU QSBR Honnappa Nagarahalli
2019-10-04 16:05       ` Medvedkin, Vladimir
2019-10-09  3:48         ` Honnappa Nagarahalli
2019-10-07  9:21       ` Ananyev, Konstantin
2019-10-13  4:36         ` Honnappa Nagarahalli
2019-10-15 11:15           ` Ananyev, Konstantin
2019-10-18  3:32             ` Honnappa Nagarahalli
2019-10-01 18:28     ` [dpdk-dev] [PATCH v3 2/3] app/test: add test case for LPM RCU integration Honnappa Nagarahalli
2019-10-01 18:28     ` [dpdk-dev] [PATCH v3 3/3] test/lpm: add RCU integration performance tests Honnappa Nagarahalli
2019-10-02 13:02       ` Aaron Conole
2019-10-03  9:09         ` Bruce Richardson
2020-06-08  5:16   ` [dpdk-dev] [PATCH v4 0/3] RCU integration with LPM library Ruifeng Wang
2020-06-08  5:16     ` [dpdk-dev] [PATCH v4 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-06-08 18:46       ` Honnappa Nagarahalli
2020-06-18 17:36         ` Medvedkin, Vladimir
2020-06-18 17:21       ` Medvedkin, Vladimir
2020-06-22  5:46         ` Ruifeng Wang
2020-06-23  4:34           ` Honnappa Nagarahalli
2020-06-08  5:16     ` [dpdk-dev] [PATCH v4 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-06-08  5:16     ` [dpdk-dev] [PATCH v4 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-06-29  8:02   ` [dpdk-dev] [PATCH v5 0/3] RCU integration with LPM library Ruifeng Wang
2020-06-29  8:02     ` [dpdk-dev] [PATCH v5 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-06-29 11:56       ` David Marchand
2020-06-29 12:55         ` Bruce Richardson
2020-06-30 10:35           ` Kinsella, Ray
2020-07-03  7:43         ` David Marchand
2020-07-04 17:00         ` Ruifeng Wang
2020-06-30 10:33       ` Kinsella, Ray
2020-06-29  8:02     ` [dpdk-dev] [PATCH v5 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-06-29  8:03     ` [dpdk-dev] [PATCH v5 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-07-07 14:40   ` [dpdk-dev] [PATCH v6 0/3] RCU integration with LPM library Ruifeng Wang
2020-07-07 14:40     ` [dpdk-dev] [PATCH v6 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-07-07 14:40     ` [dpdk-dev] [PATCH v6 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-07-07 14:40     ` [dpdk-dev] [PATCH v6 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-07-07 15:15   ` [dpdk-dev] [PATCH v7 0/3] RCU integration with LPM library Ruifeng Wang
2020-07-07 15:15     ` [dpdk-dev] [PATCH v7 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-07-08 12:36       ` Medvedkin, Vladimir
2020-07-08 14:30       ` David Marchand
2020-07-08 15:34         ` Ruifeng Wang
2020-07-07 15:15     ` [dpdk-dev] [PATCH v7 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-07-08 12:37       ` Medvedkin, Vladimir
2020-07-08 14:00         ` Ruifeng Wang
2020-07-07 15:15     ` [dpdk-dev] [PATCH v7 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-07-08 12:37       ` Medvedkin, Vladimir
2020-07-08 14:07         ` Ruifeng Wang
2020-07-09  8:02   ` [dpdk-dev] [PATCH v8 0/3] RCU integration with LPM library Ruifeng Wang
2020-07-09  8:02     ` [dpdk-dev] [PATCH v8 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-07-09 11:49       ` David Marchand
2020-07-09 14:35         ` Ruifeng Wang
2020-07-09  8:02     ` [dpdk-dev] [PATCH v8 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-07-09  8:02     ` [dpdk-dev] [PATCH v8 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-07-09 15:42   ` [dpdk-dev] [PATCH v9 0/3] RCU integration with LPM library Ruifeng Wang
2020-07-09 15:42     ` [dpdk-dev] [PATCH v9 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-07-09 15:42     ` [dpdk-dev] [PATCH v9 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-07-09 15:42     ` [dpdk-dev] [PATCH v9 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-07-10  2:22   ` [dpdk-dev] [PATCH v10 0/3] RCU integration with LPM library Ruifeng Wang
2020-07-10  2:22     ` [dpdk-dev] [PATCH v10 1/3] lib/lpm: integrate RCU QSBR Ruifeng Wang
2020-07-10  2:29       ` Ruifeng Wang
2020-07-10  2:22     ` [dpdk-dev] [PATCH v10 2/3] test/lpm: add LPM RCU integration functional tests Ruifeng Wang
2020-07-10  2:22     ` [dpdk-dev] [PATCH v10 3/3] test/lpm: add RCU integration performance tests Ruifeng Wang
2020-07-10  2:29       ` Ruifeng Wang
2020-07-10 12:21     ` [dpdk-dev] [PATCH v10 0/3] RCU integration with LPM library David Marchand
2020-07-10 14:34       ` Ruifeng Wang

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