Re: [dpdk-dev] Use WFE for spinlock and ring

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> >
> > On Sun, 25 Apr 2021 05:56:51 +0000
> > Ruifeng Wang <ruifeng.wang@arm.com> wrote:
> >
> > > The rte_wait_until_equal_xxx APIs abstract the functionality of
> > > 'polling for a memory location to become equal to a given value'[1].
> > >
> > > Use the API for the rte spinlock and ring implementations.
> > > With the wait until equal APIs being stable, changes will not impact ABI.
> > >
> > > [1] http://patches.dpdk.org/cover/62703/
> > >
> > > v3:
> > > Series rebased. (David)
> > >
> > > Gavin Hu (1):
> > >   spinlock: use wfe to reduce contention on aarch64
> > >
> > > Ruifeng Wang (1):
> > >   ring: use wfe to wait for ring tail update on aarch64
> > >
> > >  lib/eal/include/generic/rte_spinlock.h | 4 ++--
> > >  lib/ring/rte_ring_c11_pvt.h            | 4 ++--
> > >  lib/ring/rte_ring_generic_pvt.h        | 3 +--
> > >  3 files changed, 5 insertions(+), 6 deletions(-)
> > >
> >
> > Other places that should use WFE:
> Thank you Stephen for looking into this.
> 
> >
> > rte_mcslock.h:rte_mcslock_lock()
> Existing API can be used in this one.
> 
> > rte_mcslock_unlock:rte_mcslock_unlock()
> This one needs rte_wait_while_xxx variant.
> 
> >
> > rte_pflock.h:rte_pflock_lock()
> > rte_rwlock.h:rte_rwlock_read_lock()
> > rte_rwlock.h:rte_rwlock_write_lock()
> These occurrences have extra logic (AND, conditional branch, CAS) in the loop.
> I'm not sure generic API can be abstracted from these use cases.
I think it is possible to create additional abstractions to address these cases.

> 
> >
> >
> > You should also introduce rte_wait_while_XXX variants to handle some
> > of these cases.
> >
> 
>