Hi David,
> -----Original Message-----
> From: David Marchand <david.march...@redhat.com>
> Sent: Friday, October 18, 2019 2:28 AM
> To: Gavin Hu (Arm Technology China) <gavin...@arm.com>
> Cc: dev <dev@dpdk.org>; nd <n...@arm.com>; tho...@monjalon.net;
> Stephen Hemminger <step...@networkplumber.org>;
> hemant.agra...@nxp.com; jer...@marvell.com; Pavan Nikhilesh
> <pbhagavat...@marvell.com>; Honnappa Nagarahalli
> <honnappa.nagaraha...@arm.com>; Ruifeng Wang (Arm Technology China)
> <ruifeng.w...@arm.com>; Phil Yang (Arm Technology China)
> <phil.y...@arm.com>; Steve Capper <steve.cap...@arm.com>
> Subject: Re: [dpdk-dev] [PATCH v7 3/7] spinlock: use wfe to reduce
> contention on aarch64
>
> On Fri, Sep 27, 2019 at 7:43 AM Gavin Hu <gavin...@arm.com> wrote:
> >
> > In acquiring a spinlock, cores repeatedly poll the lock variable.
> > This is replaced by rte_wait_until_equal API.
> >
> > Running the micro benchmarking and the testpmd and l3fwd traffic tests
> > on ThunderX2, Ampere eMAG80 and Arm N1SDP, everything went well
> and no
> > notable performance gain nor degradation was measured.
> >
> > Signed-off-by: Gavin Hu <gavin...@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
> > Reviewed-by: Phil Yang <phil.y...@arm.com>
> > Reviewed-by: Steve Capper <steve.cap...@arm.com>
> > Reviewed-by: Ola Liljedahl <ola.liljed...@arm.com>
> > Reviewed-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> > Tested-by: Pavan Nikhilesh <pbhagavat...@marvell.com>
> > ---
> > .../common/include/arch/arm/rte_spinlock.h | 26
> ++++++++++++++++++++++
> > 1 file changed, 26 insertions(+)
> >
> > diff --git a/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
> b/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
> > index 1a6916b..b61c055 100644
> > --- a/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
> > +++ b/lib/librte_eal/common/include/arch/arm/rte_spinlock.h
> > @@ -16,6 +16,32 @@ extern "C" {
> > #include <rte_common.h>
> > #include "generic/rte_spinlock.h"
> >
> > +/* armv7a does support WFE, but an explicit wake-up signal using SEV is
> > + * required (must be preceded by DSB to drain the store buffer) and
> > + * this is less performant, so keep armv7a implementation unchanged.
> > + */
> > +#ifndef RTE_FORCE_INTRINSICS
>
> Earlier, in the same file, I can see:
> https://git.dpdk.org/dpdk/tree/lib/librte_eal/common/include/arch/arm/rte
> _spinlock.h?h=v19.08#n8
>
> #ifndef RTE_FORCE_INTRINSICS
> # error Platform must be built with CONFIG_RTE_FORCE_INTRINSICS
> #endif
>
> IIUC, this is dead code.
Yes, will remove in next version.
>
> > +static inline void
> > +rte_spinlock_lock(rte_spinlock_t *sl)
> > +{
> > + unsigned int tmp;
> > + /* http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.
> > + * faqs/ka16809.html
> > + */
> > + asm volatile(
> > + "1: ldaxr %w[tmp], %w[locked]\n"
> > + "cbnz %w[tmp], 2f\n"
> > + "stxr %w[tmp], %w[one], %w[locked]\n"
> > + "cbnz %w[tmp], 1b\n"
> > + "ret\n"
> > + "2: sevl\n"
> > + "wfe\n"
> > + "jmp 1b\n"
> > + : [tmp] "=&r" (tmp), [locked] "+Q"(sl->locked)
> > + : [one] "r" (1)
> > +}
> > +#endif
> > +
> > static inline int rte_tm_supported(void)
> > {
> > return 0;
> > --
> > 2.7.4
> >
>
>
> --
> David Marchand
