linux-kernel - [PATCH 3/6] MIPS: Octeon: qspinlock: Flush write buffer

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Date:   Wed, 27 Jan 2021 21:36:24 +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 3/6] MIPS: Octeon: qspinlock: Flush write buffer

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

Flushing the write buffer brings aroung 10% performace on the tight
uncontended spinlock loops on Octeon. Refer to commit 500c2e1fdbcc
("MIPS: Optimize spinlocks.").

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
---
 arch/mips/include/asm/spinlock.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
index 8a88eb2..0a707f3 100644
--- a/arch/mips/include/asm/spinlock.h
+++ b/arch/mips/include/asm/spinlock.h
@@ -24,6 +24,9 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
 	/* This could be optimised with ARCH_HAS_MMIOWB */
 	mmiowb();
 	smp_store_release(&lock->locked, 0);
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+	nudge_writes();
+#endif
 }
 
 #include <asm/qspinlock.h>
-- 
2.10.2