DPDK patches and discussions
 help / color / mirror / Atom feed
From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
To: konstantin.ananyev@intel.com, stephen@networkplumber.org,
	vladimir.medvedkin@intel.com, dev@dpdk.org
Cc: honnappa.nagarahalli@arm.com, david.marchand@redhat.com,
	ruifeng.wang@arm.com, dharmik.thakkar@arm.com, nd@arm.com
Subject: [dpdk-dev] [PATCH v5 3/4] doc/rcu: add RCU integration design details
Date: Tue, 21 Apr 2020 22:30:05 -0500
Message-ID: <20200422033006.1124-4-honnappa.nagarahalli@arm.com> (raw)
In-Reply-To: <20200422033006.1124-1-honnappa.nagarahalli@arm.com>

From: Ruifeng Wang <ruifeng.wang@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>
Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 doc/guides/prog_guide/rcu_lib.rst | 59 +++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/doc/guides/prog_guide/rcu_lib.rst b/doc/guides/prog_guide/rcu_lib.rst
index 9b0bf138f..60468f143 100644
--- a/doc/guides/prog_guide/rcu_lib.rst
+++ b/doc/guides/prog_guide/rcu_lib.rst
@@ -190,3 +190,62 @@ 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.
+
+Resource reclamation framework for DPDK
+---------------------------------------
+
+Lock-free algorithms place additional burden of resource reclamation on
+the application. When a writer deletes an entry from a data structure, the writer:
+
+#. Has to start the grace period
+#. Has to store a reference to the deleted resources in a FIFO
+#. Should check if the readers have completed a grace period and free the resources.
+
+There are several APIs provided to help with this process. The writer
+can create a FIFO to store the references to deleted resources using ``rte_rcu_qsbr_dq_create()``.
+The resources can be enqueued to this FIFO using ``rte_rcu_qsbr_dq_enqueue()``.
+If the FIFO is full, ``rte_rcu_qsbr_dq_enqueue`` will reclaim the resources before enqueuing. It will also reclaim resources on regular basis to keep the FIFO from growing too large. If the writer runs out of resources, the writer can call ``rte_rcu_qsbr_dq_reclaim`` API to reclaim resources. ``rte_rcu_qsbr_dq_delete`` is provided to reclaim any remaining resources and free the FIFO while shutting down.
+
+However, if this resource reclamation process were to be integrated in lock-free data structure libraries, it
+hides this complexity from the application and makes it easier for the application to adopt lock-free algorithms. The following paragraphs discuss how the reclamation process can be integrated in DPDK libraries.
+
+In any DPDK application, the resource 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 lock-free 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. It should call ``rte_rcu_qsbr_dq_create()`` to create the FIFO to store the references to deleted entries.
+* client library should use ``rte_rcu_qsbr_dq_enqueue`` to enqueue the deleted resources on the FIFO and start the grace period.
+* if the library runs out of resources while adding entries, it should call ``rte_rcu_qsbr_dq_reclaim`` to reclaim the resources and try the resource allocation again.
+
+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 call ``rte_rcu_qsbr_dq_delete`` to reclaim any remaining resources and free the FIFO.
+
+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


  parent reply	other threads:[~2020-04-22  3:30 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
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       ` Honnappa Nagarahalli [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200422033006.1124-4-honnappa.nagarahalli@arm.com \
    --to=honnappa.nagarahalli@arm.com \
    --cc=david.marchand@redhat.com \
    --cc=dev@dpdk.org \
    --cc=dharmik.thakkar@arm.com \
    --cc=konstantin.ananyev@intel.com \
    --cc=nd@arm.com \
    --cc=ruifeng.wang@arm.com \
    --cc=stephen@networkplumber.org \
    --cc=vladimir.medvedkin@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git