-----Original Message-----
> Date: Thu, 18 May 2017 17:40:58 +0800
> From: Jianbo Liu <jianbo....@linaro.org>
> To: Jerin Jacob <jerin.ja...@caviumnetworks.com>
> Cc: dev@dpdk.org, tho...@monjalon.net, Jan Viktorin
> <vikto...@rehivetech.com>
> Subject: Re: [dpdk-dev] [PATCH 3/6] eal/arm64: rte pause implementation for
> arm64
>
> On 11 May 2017 at 18:10, Jerin Jacob <jerin.ja...@caviumnetworks.com> wrote:
> > CC: Jianbo Liu <jianbo....@linaro.org>
> > Signed-off-by: Jerin Jacob <jerin.ja...@caviumnetworks.com>
> > ---
> > lib/librte_eal/common/include/arch/arm/rte_pause.h | 4 ++
> > .../common/include/arch/arm/rte_pause_64.h | 55
> > ++++++++++++++++++++++
> > 2 files changed, 59 insertions(+)
> > create mode 100644 lib/librte_eal/common/include/arch/arm/rte_pause_64.h
> >
> > diff --git a/lib/librte_eal/common/include/arch/arm/rte_pause.h
> > b/lib/librte_eal/common/include/arch/arm/rte_pause.h
> > index 0fe88aba9..9b79405e6 100644
> > --- a/lib/librte_eal/common/include/arch/arm/rte_pause.h
> > +++ b/lib/librte_eal/common/include/arch/arm/rte_pause.h
> > @@ -37,7 +37,11 @@
> > extern "C" {
> > #endif
> >
> > +#ifdef RTE_ARCH_64
> > +#include <rte_pause_64.h>
> > +#else
> > #include <rte_pause_32.h>
> > +#endif
> >
> > #ifdef __cplusplus
> > }
> > diff --git a/lib/librte_eal/common/include/arch/arm/rte_pause_64.h
> > b/lib/librte_eal/common/include/arch/arm/rte_pause_64.h
> > new file mode 100644
> > index 000000000..cae996de8
> > --- /dev/null
> > +++ b/lib/librte_eal/common/include/arch/arm/rte_pause_64.h
> > @@ -0,0 +1,55 @@
> > +/*
> > + * BSD LICENSE
> > + *
> > + * Copyright(c) 2017 Cavium. All rights reserved.
> > + *
> > + * Redistribution and use in source and binary forms, with or without
> > + * modification, are permitted provided that the following conditions
> > + * are met:
> > + *
> > + * * Redistributions of source code must retain the above copyright
> > + * notice, this list of conditions and the following disclaimer.
> > + * * Redistributions in binary form must reproduce the above copyright
> > + * notice, this list of conditions and the following disclaimer in
> > + * the documentation and/or other materials provided with the
> > + * distribution.
> > + * * Neither the name of Cavium nor the names of its
> > + * contributors may be used to endorse or promote products derived
> > + * from this software without specific prior written permission.
> > + *
> > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> > + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> > + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> > + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
> > + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> > + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> > + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> > + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> > + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> > + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
> > + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
> > + */
> > +
> > +#ifndef _RTE_PAUSE_ARM64_H_
> > +#define _RTE_PAUSE_ARM64_H_
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif
> > +
> > +#include <rte_common.h>
> > +#include "generic/rte_pause.h"
> > +
> > +static inline void rte_pause(void)
> > +{
> > + /* YIELD hints the CPU to switch to another thread if possible
> > + * and executes as a NOP otherwise.
>
> I think you can remove the second line if you are trying to explain
> what YIELD instruction is.
> And I wonder if it can save power as rte_thread is bounded to certain
> core and always polling while YIELD is only a hint instruction.
AFAIK, It is HW thread not software OS thread.ie Simultaneous Multi-Threading
(SMT)
or Hyper threading.
For example, Cavium 99xx has 4 HW threads per physical core.
I agree on comment. I think, I can remove the comment as YIELD is just a hint
and varies based on arm64 implementation. Will fix it v2.
>
> > + */
> > + asm volatile("yield" ::: "memory");
> > +}
> > +
> > +#ifdef __cplusplus
> > +}
> > +#endif
> > +
> > +#endif /* _RTE_PAUSE_ARM64_H_ */
> > --
> > 2.12.2
> >
