linux-kernel - [PATCH 0/3] Introduce load_acquire() and store

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Date:	Thu, 13 Nov 2014 11:27:10 -0800
From:	Alexander Duyck <alexander.h.duyck@...hat.com>
To:	linux-arch@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	mikey@...ling.org, tony.luck@...el.com,
	mathieu.desnoyers@...ymtl.ca, donald.c.skidmore@...el.com,
	peterz@...radead.org, benh@...nel.crashing.org,
	heiko.carstens@...ibm.com, oleg@...hat.com, will.deacon@....com,
	davem@...emloft.net, michael@...erman.id.au,
	matthew.vick@...el.com, nic_swsd@...ltek.com, geert@...ux-m68k.org,
	jeffrey.t.kirsher@...el.com, fweisbec@...il.com,
	schwidefsky@...ibm.com, linux@....linux.org.uk,
	paulmck@...ux.vnet.ibm.com, torvalds@...ux-foundation.org,
	mingo@...nel.org
Subject: [PATCH 0/3] Introduce load_acquire() and store_release()

These patches introduce uniprocessor or CPU<->device equivalents for
smp_load_acquire() and smp_store_release().  These two new primitives are:

	load_acquire()
	store_release()

The first patch adds the primitives for the applicable architectures and
asm-generic.

The second patch adds the primitives to r8169 which turns out to be a good
example of where the new primitives might be useful as they have memory
barriers ordering accesses to the descriptors and the DescOwn bit within the
descriptors which follow acquire/release style semantics.

The third patch adds support for load_acquire() to the Intel fm10k, igb,
and ixgbe drivers.  Testing with the ixgbe driver has shown a processing
time reduction of at least 7ns per 64B frame on a Core i7-4930K.

This patch series is essentially the v2 for:
	arch: Introduce read_acquire()

The key changes in this patch series versus that patch are:
	- Renamed read_acquire() to be consistent with smp_load_acquire()
	- Changed barrier used to be consistent with smp_load_acquire()
	- Updated PowerPC code to use __lwsync based on IBM article
	- Added store_release() as this is a viable use case for drivers
	- Added r8169 patch which is able to fully use primitives
	- Added fm10k/igb/ixgbe patch which is able to test performance

---

Alexander Duyck (3):
      arch: Introduce load_acquire() and store_release()
      r8169: Use load_acquire() and store_release() to reduce memory barrier overhead
      fm10k/igb/ixgbe: Use load_acquire on Rx descriptor


 arch/arm/include/asm/barrier.h                |   15 ++++++
 arch/arm64/include/asm/barrier.h              |   59 +++++++++++++------------
 arch/ia64/include/asm/barrier.h               |    7 ++-
 arch/metag/include/asm/barrier.h              |   15 ++++++
 arch/mips/include/asm/barrier.h               |   15 ++++++
 arch/powerpc/include/asm/barrier.h            |   24 ++++++++--
 arch/s390/include/asm/barrier.h               |    7 ++-
 arch/sparc/include/asm/barrier_64.h           |    6 ++-
 arch/x86/include/asm/barrier.h                |   22 ++++++++-
 drivers/net/ethernet/intel/fm10k/fm10k_main.c |    8 +--
 drivers/net/ethernet/intel/igb/igb_main.c     |    8 +--
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   11 ++---
 drivers/net/ethernet/realtek/r8169.c          |   23 ++++------
 include/asm-generic/barrier.h                 |   15 ++++++
 14 files changed, 163 insertions(+), 72 deletions(-)

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