From: Peter Zijlstra <peterz@infradead•org>
To: Torsten Duwe <duwe@lst•de>
Cc: linux-kernel@vger•kernel.org, Paul Mackerras <paulus@samba•org>,
Anton Blanchard <anton@samba•org>,
"Paul E. McKenney" <paulmck@linux•vnet.ibm.com>,
linuxppc-dev@lists•ozlabs.org, Ingo Molnar <mingo@kernel•org>
Subject: Re: [PATCH] Convert powerpc simple spinlocks into ticket locks
Date: Thu, 6 Feb 2014 17:38:37 +0100 [thread overview]
Message-ID: <20140206163837.GT2936@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <20140206103736.GA18054@lst.de>
On Thu, Feb 06, 2014 at 11:37:37AM +0100, Torsten Duwe wrote:
> x86 has them, MIPS has them, ARM has them, even ia64 has them:
> ticket locks. They reduce memory bus and cache pressure especially
> for contended spinlocks, increasing performance.
>
> This patch is a port of the x86 spin locks, mostly written in C,
> to the powerpc, introducing inline asm where needed. The pSeries
> directed yield for vCPUs is taken care of by an additional "holder"
> field in the lock.
>
A few questions; what's with the ppc64 holder thing? Not having a 32bit
spinlock_t is sad.
Can you pair lwarx with sthcx ? I couldn't immediately find the answer
in the PowerISA doc. If so I think you can do better by being able to
atomically load both tickets but only storing the head without affecting
the tail.
In that case you can avoid the ll/sc on unlock, because only the lock
owner can modify the tail, so you can use a single half-word store.
next prev parent reply other threads:[~2014-02-06 16:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-06 10:37 [PATCH] Convert powerpc simple spinlocks into ticket locks Torsten Duwe
2014-02-06 15:53 ` Benjamin Herrenschmidt
2014-02-06 16:38 ` Peter Zijlstra [this message]
2014-02-06 17:37 ` Torsten Duwe
2014-02-06 18:08 ` Peter Zijlstra
2014-02-06 19:28 ` Tom Musta
2014-02-10 2:54 ` Benjamin Herrenschmidt
2014-02-07 8:24 ` Torsten Duwe
2014-02-06 20:19 ` Scott Wood
2014-02-07 9:02 ` Torsten Duwe
2014-02-07 10:31 ` Peter Zijlstra
2014-02-07 10:36 ` Peter Zijlstra
2014-02-07 10:45 ` Peter Zijlstra
2014-02-07 11:49 ` Torsten Duwe
2014-02-07 12:28 ` Peter Zijlstra
2014-02-07 15:18 ` Peter Zijlstra
2014-02-07 15:43 ` Peter Zijlstra
2014-02-07 17:08 ` Torsten Duwe
2014-02-07 17:19 ` Peter Zijlstra
2014-02-07 15:51 ` Kumar Gala
2014-02-07 16:10 ` Peter Zijlstra
2014-02-10 3:05 ` Benjamin Herrenschmidt
2014-02-10 3:02 ` Benjamin Herrenschmidt
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