Re: [RFC ][PATCH] Introduce RTE_ARCH_STRONGLY_ORDERED_MEM_OPS configuration parameter

[simon barber <sbarber@brocade.com>]

Do we need to have all these #ifdef, it looks messy, can you not define 
a macro that is defined based upon

  
RTE_ARCH_STRONGLY_ORDERED_MEM_OP


/Simon


On 11/03/2015 03:52 PM, Jerin Jacob wrote:
> 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.
>
> 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;