From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
To: honnappa.nagarahalli@arm.com, olivier.matz@6wind.com,
anatoly.burakov@intel.com
Cc: dev@dpdk.org, nd@arm.com
Subject: [dpdk-dev] [PATCH v4] rte_ring: clarify preemptible nature of ring algorithm
Date: Mon, 16 Jul 2018 23:52:44 -0500 [thread overview]
Message-ID: <1531803164-46516-1-git-send-email-honnappa.nagarahalli@arm.com> (raw)
rte_ring implementation is not preemptible only under certain
circumstances. This clarification is helpful for data plane and
control plane communication using rte_ring.
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
---
v4:
* Undo few changes (Anatoly, Oliver)
v3:
* Corrected known issues for rte_ring
* Referred to known issues in rte_ring.h (Anatoly, Oliver)
v2:
* Fixed checkpatch warnings
doc/guides/prog_guide/env_abstraction_layer.rst | 12 ++++++++----
lib/librte_ring/rte_ring.h | 5 +++--
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
index a22640d..99d259f 100644
--- a/doc/guides/prog_guide/env_abstraction_layer.rst
+++ b/doc/guides/prog_guide/env_abstraction_layer.rst
@@ -445,13 +445,17 @@ Known Issues
Bypassing this constraint may cause the 2nd pthread to spin until the 1st one is scheduled again.
Moreover, if the 1st pthread is preempted by a context that has an higher priority, it may even cause a dead lock.
- This does not mean it cannot be used, simply, there is a need to narrow down the situation when it is used by multi-pthread on the same core.
+ This means, use cases involving preemptible pthreads should consider using rte_ring carefully.
- 1. It CAN be used for any single-producer or single-consumer situation.
+ 1. It CAN be used for preemptible single-producer and single-consumer use case.
- 2. It MAY be used by multi-producer/consumer pthread whose scheduling policy are all SCHED_OTHER(cfs). User SHOULD be aware of the performance penalty before using it.
+ 2. It CAN be used for non-preemptible multi-producer and preemptible single-consumer use case.
- 3. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR.
+ 3. It CAN be used for preemptible single-producer and non-preemptible multi-consumer use case.
+
+ 4. It MAY be used by preemptible multi-producer and/or preemptible multi-consumer pthreads whose scheduling policy are all SCHED_OTHER(cfs), SCHED_IDLE or SCHED_BATCH. User SHOULD be aware of the performance penalty before using it.
+
+ 5. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR.
+ rte_timer
diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index 1245822..e680101 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -26,8 +26,9 @@
* - Bulk dequeue.
* - Bulk enqueue.
*
- * Note: the ring implementation is not preemptable. A lcore must not
- * be interrupted by another task that uses the same ring.
+ * Note: the ring implementation is not preemptible. Refer to Programmer's
+ * guide/Environment Abstraction Layer/Multiple pthread/Known Issues/rte_ring
+ * for more information.
*
*/
--
2.7.4
next reply other threads:[~2018-07-17 4:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-17 4:52 Honnappa Nagarahalli [this message]
2018-08-03 15:09 ` Olivier Matz
2018-08-05 13:40 ` Thomas Monjalon
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