From: Alexander A Sverdlin <alexander.sverdlin@nokia.com>
To: Paul Burton <paul.burton@imgtec.com>, linux-mips@vger.kernel.org
Cc: Alexander Sverdlin <alexander.sverdlin@nokia.com>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Boqun Feng <boqun.feng@gmail.com>, Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 6/6] MIPS: cmpxchg: Use cmpxchg_local() for {cmp_}xchg_small()
Date: Wed, 27 Jan 2021 21:36:27 +0100 [thread overview]
Message-ID: <20210127203627.47510-7-alexander.sverdlin@nokia.com> (raw)
In-Reply-To: <20210127203627.47510-1-alexander.sverdlin@nokia.com>
From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
It makes no sense to fold smp_mb__before_llsc()/smp_llsc_mb() again and
again, leave only one barrier pair in the outer function.
This removes one SYNCW from __xchg_small() and brings around 10%
performance improvement in a tight spinlock loop with 6 threads on a 6 core
Octeon.
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
---
arch/mips/kernel/cmpxchg.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/mips/kernel/cmpxchg.c b/arch/mips/kernel/cmpxchg.c
index 89107de..122e85f 100644
--- a/arch/mips/kernel/cmpxchg.c
+++ b/arch/mips/kernel/cmpxchg.c
@@ -41,7 +41,7 @@ unsigned long __xchg_small(volatile void *ptr, unsigned long val, unsigned int s
do {
old32 = load32;
new32 = (load32 & ~mask) | (val << shift);
- load32 = cmpxchg(ptr32, old32, new32);
+ load32 = cmpxchg_local(ptr32, old32, new32);
} while (load32 != old32);
return (load32 & mask) >> shift;
@@ -97,7 +97,7 @@ unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
*/
old32 = (load32 & ~mask) | (old << shift);
new32 = (load32 & ~mask) | (new << shift);
- load32 = cmpxchg(ptr32, old32, new32);
+ load32 = cmpxchg_local(ptr32, old32, new32);
if (load32 == old32)
return old;
}
--
2.10.2
next prev parent reply other threads:[~2021-01-27 20:38 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 20:36 [PATCH 0/6] MIPS: qspinlock: Try to reduce reduce the spinlock regression Alexander A Sverdlin
2021-01-27 20:36 ` [PATCH 1/6] MIPS: Octeon: Implement __smp_store_release() Alexander A Sverdlin
2021-01-27 22:32 ` Peter Zijlstra
2021-01-28 7:27 ` Alexander Sverdlin
2021-01-28 11:33 ` Peter Zijlstra
2021-01-28 11:52 ` Alexander Sverdlin
2021-01-28 14:57 ` Peter Zijlstra
2021-01-28 15:15 ` Peter Zijlstra
2021-01-28 12:09 ` Alexander Sverdlin
2021-01-28 15:04 ` Peter Zijlstra
2021-01-27 20:36 ` [PATCH 2/6] MIPS: Implement atomic_cmpxchg_relaxed() Alexander A Sverdlin
2021-01-27 20:36 ` [PATCH 3/6] MIPS: Octeon: qspinlock: Flush write buffer Alexander A Sverdlin
2021-01-27 22:34 ` Peter Zijlstra
2021-01-28 7:29 ` Alexander Sverdlin
2021-01-28 11:35 ` Peter Zijlstra
2021-01-28 12:13 ` Alexander Sverdlin
2021-01-28 15:26 ` Peter Zijlstra
2021-01-27 20:36 ` [PATCH 4/6] MIPS: Octeon: qspinlock: Exclude mmiowb() Alexander A Sverdlin
2021-01-27 22:35 ` Peter Zijlstra
2021-01-27 20:36 ` [PATCH 5/6] MIPS: Provide {atomic_}xchg_relaxed() Alexander A Sverdlin
2021-01-27 20:36 ` Alexander A Sverdlin [this message]
2021-01-27 22:37 ` [PATCH 6/6] MIPS: cmpxchg: Use cmpxchg_local() for {cmp_}xchg_small() Peter Zijlstra
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