Re: [dpdk-dev] [RFC ][PATCH] Introduce RTE_ARCH_STRONGLY_ORDERED_MEM_OPS configuration parameter

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jerin Jacob
> Sent: Tuesday, November 03, 2015 3:52 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [RFC ][PATCH] Introduce RTE_ARCH_STRONGLY_ORDERED_MEM_OPS configuration parameter
> 
> rte_ring implementation needs explicit memory barrier
> in weakly ordered architecture like ARM unlike
> strongly ordered architecture like X86
> 
> Introducing RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
> configuration to abstract such dependency so that other
> weakly ordered architectures can reuse this infrastructure.

Looks a bit clumsy.
Please try to follow this suggestion instead:
http://dpdk.org/ml/archives/dev/2015-October/025505.html

Konstantin

> 
> Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> ---
>  config/common_bsdapp                         |  5 +++++
>  config/common_linuxapp                       |  5 +++++
>  config/defconfig_arm64-armv8a-linuxapp-gcc   |  1 +
>  config/defconfig_arm64-thunderx-linuxapp-gcc |  1 +
>  lib/librte_ring/rte_ring.h                   | 20 ++++++++++++++++++++
>  5 files changed, 32 insertions(+)
> 
> diff --git a/config/common_bsdapp b/config/common_bsdapp
> index b37dcf4..c8d1f63 100644
> --- a/config/common_bsdapp
> +++ b/config/common_bsdapp
> @@ -79,6 +79,11 @@ CONFIG_RTE_FORCE_INTRINSICS=n
>  CONFIG_RTE_ARCH_STRICT_ALIGN=n
> 
>  #
> +# Machine has strongly-ordered memory operations on normal memory like x86
> +#
> +CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=y
> +
> +#
>  # Compile to share library
>  #
>  CONFIG_RTE_BUILD_SHARED_LIB=n
> diff --git a/config/common_linuxapp b/config/common_linuxapp
> index 0de43d5..d040a74 100644
> --- a/config/common_linuxapp
> +++ b/config/common_linuxapp
> @@ -79,6 +79,11 @@ CONFIG_RTE_FORCE_INTRINSICS=n
>  CONFIG_RTE_ARCH_STRICT_ALIGN=n
> 
>  #
> +# Machine has strongly-ordered memory operations on normal memory like x86
> +#
> +CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=y
> +
> +#
>  # Compile to share library
>  #
>  CONFIG_RTE_BUILD_SHARED_LIB=n
> diff --git a/config/defconfig_arm64-armv8a-linuxapp-gcc b/config/defconfig_arm64-armv8a-linuxapp-gcc
> index 6ea38a5..5289152 100644
> --- a/config/defconfig_arm64-armv8a-linuxapp-gcc
> +++ b/config/defconfig_arm64-armv8a-linuxapp-gcc
> @@ -37,6 +37,7 @@ CONFIG_RTE_ARCH="arm64"
>  CONFIG_RTE_ARCH_ARM64=y
>  CONFIG_RTE_ARCH_64=y
>  CONFIG_RTE_ARCH_ARM_NEON=y
> +CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=n
> 
>  CONFIG_RTE_FORCE_INTRINSICS=y
> 
> diff --git a/config/defconfig_arm64-thunderx-linuxapp-gcc b/config/defconfig_arm64-thunderx-linuxapp-gcc
> index e8fccc7..79fa9e6 100644
> --- a/config/defconfig_arm64-thunderx-linuxapp-gcc
> +++ b/config/defconfig_arm64-thunderx-linuxapp-gcc
> @@ -37,6 +37,7 @@ CONFIG_RTE_ARCH="arm64"
>  CONFIG_RTE_ARCH_ARM64=y
>  CONFIG_RTE_ARCH_64=y
>  CONFIG_RTE_ARCH_ARM_NEON=y
> +CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=n
> 
>  CONFIG_RTE_FORCE_INTRINSICS=y
> 
> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
> index af68888..1ccd186 100644
> --- a/lib/librte_ring/rte_ring.h
> +++ b/lib/librte_ring/rte_ring.h
> @@ -457,7 +457,12 @@ __rte_ring_mp_do_enqueue(struct rte_ring *r, void * const *obj_table,
> 
>  	/* write entries in ring */
>  	ENQUEUE_PTRS();
> +
> +#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
>  	rte_compiler_barrier();
> +#else
> +	rte_wmb();
> +#endif
> 
>  	/* if we exceed the watermark */
>  	if (unlikely(((mask + 1) - free_entries + n) > r->prod.watermark)) {
> @@ -552,7 +557,12 @@ __rte_ring_sp_do_enqueue(struct rte_ring *r, void * const *obj_table,
> 
>  	/* write entries in ring */
>  	ENQUEUE_PTRS();
> +
> +#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
>  	rte_compiler_barrier();
> +#else
> +	rte_wmb();
> +#endif
> 
>  	/* if we exceed the watermark */
>  	if (unlikely(((mask + 1) - free_entries + n) > r->prod.watermark)) {
> @@ -643,7 +653,12 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void **obj_table,
> 
>  	/* copy in table */
>  	DEQUEUE_PTRS();
> +
> +#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
>  	rte_compiler_barrier();
> +#else
> +	rte_rmb();
> +#endif
> 
>  	/*
>  	 * If there are other dequeues in progress that preceded us,
> @@ -727,7 +742,12 @@ __rte_ring_sc_do_dequeue(struct rte_ring *r, void **obj_table,
> 
>  	/* copy in table */
>  	DEQUEUE_PTRS();
> +
> +#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
>  	rte_compiler_barrier();
> +#else
> +	rte_rmb();
> +#endif
> 
>  	__RING_STAT_ADD(r, deq_success, n);
>  	r->cons.tail = cons_next;
> --
> 2.1.0