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

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Tue, Nov 03, 2015 at 03:57:24PM +0000, Ananyev, Konstantin wrote:
> 
> 
> > -----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

Make sense. Do we agree on a macro that is defined based upon
RTE_ARCH_STRONGLY_ORDERED_MEM_OP to remove clumsy #ifdef every where ?

Jerin

> 
> 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
>