From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Burton <paul.burton@imgtec.com>,
linux-mips@vger.kernel.org,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Will Deacon <will@kernel.org>, Boqun Feng <boqun.feng@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/6] MIPS: Octeon: qspinlock: Flush write buffer
Date: Thu, 28 Jan 2021 08:29:57 +0100 [thread overview]
Message-ID: <f492b29b-32a4-b4d4-a5d3-0d0dd8a56b5a@nokia.com> (raw)
In-Reply-To: <YBHqeXPMILg+352D@hirez.programming.kicks-ass.net>
Hi!
On 27/01/2021 23:34, Peter Zijlstra wrote:
> On Wed, Jan 27, 2021 at 09:36:24PM +0100, Alexander A Sverdlin wrote:
>> From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
>>
>> Flushing the write buffer brings aroung 10% performace on the tight
>> uncontended spinlock loops on Octeon. Refer to commit 500c2e1fdbcc
>> ("MIPS: Optimize spinlocks.").
> No objection to the patch, but I don't find the above referenced commit
> to be enlightening wrt nudge_writes(). The best it has to offer is the
> comment that's already in the code.
My point was that original MIPS spinlocks had this write-buffer-flush and
it got lost on the conversion to qspinlocks. The referenced commit just
allows to see the last MIPS-specific implementation before deletion.
>> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.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>
--
Best regards,
Alexander Sverdlin.
next prev parent reply other threads:[~2021-01-28 7:33 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 [this message]
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 ` [PATCH 6/6] MIPS: cmpxchg: Use cmpxchg_local() for {cmp_}xchg_small() Alexander A Sverdlin
2021-01-27 22:37 ` Peter Zijlstra
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