-----Original Message-----
From: Stephen Hemminger <stephen@networkplumber.org>
Sent: Wednesday, July 7, 2021 10:48 PM
To: Ruifeng Wang <redacted>
Cc: dev@dpdk.org; david.marchand@redhat.com; thomas@monjalon.net;
jerinj@marvell.com; nd [off-list ref]; Honnappa Nagarahalli
[off-list ref]
Subject: Re: [dpdk-dev] Use WFE for spinlock and ring

On Sun, 25 Apr 2021 05:56:51 +0000
Ruifeng Wang [off-list ref] wrote:

quoted

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.

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