linux-kernel - [PATCH 0/6] MIPS: qspinlock: Try to reduce reduce the spinlock regression

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Date:   Wed, 27 Jan 2021 21:36:21 +0100
From:   Alexander A Sverdlin <alexander.sverdlin@...ia.com>
To:     Paul Burton <paul.burton@...tec.com>, linux-mips@...r.kernel.org
Cc:     Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 0/6] MIPS: qspinlock: Try to reduce reduce the spinlock regression

From: Alexander Sverdlin <alexander.sverdlin@...ia.com>

The switch to qspinlock brought a massive regression in spinlocks on
Octeon. Even after applying this series (and a patch in the
ARCH-independent code [1]) tight contended (6 cores, 1 thread per core)
spinlock loop is still 50% slower as previous ticket-based implementation.

This series implements some optimizations and has been tested on a 6-core
Octeon machine.

[1] Link: https://lkml.org/lkml/2021/1/27/1137

Alexander Sverdlin (6):
  MIPS: Octeon: Implement __smp_store_release()
  MIPS: Implement atomic_cmpxchg_relaxed()
  MIPS: Octeon: qspinlock: Flush write buffer
  MIPS: Octeon: qspinlock: Exclude mmiowb()
  MIPS: Provide {atomic_}xchg_relaxed()
  MIPS: cmpxchg: Use cmpxchg_local() for {cmp_}xchg_small()

 arch/mips/include/asm/atomic.h   | 5 +++++
 arch/mips/include/asm/barrier.h  | 9 +++++++++
 arch/mips/include/asm/cmpxchg.h  | 6 ++++++
 arch/mips/include/asm/spinlock.h | 5 +++++
 arch/mips/kernel/cmpxchg.c       | 4 ++--
 5 files changed, 27 insertions(+), 2 deletions(-)

-- 
2.10.2