From: Torsten Duwe <duwe@lst.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Tom Musta <tommusta@gmail.com>,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>,
Scott Wood <scottwood@freescale.com>,
"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: Fri, 7 Feb 2014 12:49:49 +0100 [thread overview]
Message-ID: <20140207114949.GA2107@lst.de> (raw)
In-Reply-To: <20140207104530.GG5126@laptop.programming.kicks-ass.net>
On Fri, Feb 07, 2014 at 11:45:30AM +0100, Peter Zijlstra wrote:
>
> That might need to be lhz too, I'm confused on all the load variants.
;-)
> > unlock:
> > lhz %0, 0, &tail
> > addic %0, %0, 1
No carry with this one, I'd say.
Besides, unlock increments the head.
> > lwsync
> > sth %0, 0, &tail
> >
Given the beauty and simplicity of this, may I ask Ingo:
you signed off 314cdbefd1fd0a7acf3780e9628465b77ea6a836;
can you explain why head and tail must live on the same cache
line? Or is it just a space saver? I just ported it to ppc,
I didn't think about alternatives.
What about
atomic_t tail;
volatile int head; ?
Admittedly, that's usually 8 bytes instead of 4...
Torsten
WARNING: multiple messages have this Message-ID (diff)
From: Torsten Duwe <duwe@lst.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Wood <scottwood@freescale.com>,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>, Tom Musta <tommusta@gmail.com>,
"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: Fri, 7 Feb 2014 12:49:49 +0100 [thread overview]
Message-ID: <20140207114949.GA2107@lst.de> (raw)
In-Reply-To: <20140207104530.GG5126@laptop.programming.kicks-ass.net>
On Fri, Feb 07, 2014 at 11:45:30AM +0100, Peter Zijlstra wrote:
>
> That might need to be lhz too, I'm confused on all the load variants.
;-)
> > unlock:
> > lhz %0, 0, &tail
> > addic %0, %0, 1
No carry with this one, I'd say.
Besides, unlock increments the head.
> > lwsync
> > sth %0, 0, &tail
> >
Given the beauty and simplicity of this, may I ask Ingo:
you signed off 314cdbefd1fd0a7acf3780e9628465b77ea6a836;
can you explain why head and tail must live on the same cache
line? Or is it just a space saver? I just ported it to ppc,
I didn't think about alternatives.
What about
atomic_t tail;
volatile int head; ?
Admittedly, that's usually 8 bytes instead of 4...
Torsten
next prev parent reply other threads:[~2014-02-07 11:49 UTC|newest]
Thread overview: 45+ 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 10:37 ` Torsten Duwe
2014-02-06 15:53 ` Benjamin Herrenschmidt
2014-02-06 15:53 ` Benjamin Herrenschmidt
2014-02-06 16:38 ` Peter Zijlstra
2014-02-06 16:38 ` Peter Zijlstra
2014-02-06 17:37 ` Torsten Duwe
2014-02-06 17:37 ` Torsten Duwe
2014-02-06 18:08 ` Peter Zijlstra
2014-02-06 18:08 ` Peter Zijlstra
2014-02-06 19:28 ` Tom Musta
2014-02-10 2:54 ` Benjamin Herrenschmidt
2014-02-10 2:54 ` Benjamin Herrenschmidt
2014-02-07 8:24 ` Torsten Duwe
2014-02-07 8:24 ` Torsten Duwe
2014-02-06 20:19 ` Scott Wood
2014-02-06 20:19 ` Scott Wood
2014-02-07 9:02 ` Torsten Duwe
2014-02-07 9:02 ` Torsten Duwe
2014-02-07 10:31 ` Peter Zijlstra
2014-02-07 10:31 ` Peter Zijlstra
2014-02-07 10:36 ` Peter Zijlstra
2014-02-07 10:36 ` Peter Zijlstra
2014-02-07 10:45 ` Peter Zijlstra
2014-02-07 10:45 ` Peter Zijlstra
2014-02-07 11:49 ` Torsten Duwe [this message]
2014-02-07 11:49 ` Torsten Duwe
2014-02-07 12:28 ` Peter Zijlstra
2014-02-07 12:28 ` Peter Zijlstra
2014-02-07 15:18 ` Peter Zijlstra
2014-02-07 15:18 ` Peter Zijlstra
2014-02-07 15:43 ` Peter Zijlstra
2014-02-07 15:43 ` Peter Zijlstra
2014-02-07 17:08 ` Torsten Duwe
2014-02-07 17:08 ` Torsten Duwe
2014-02-07 17:19 ` Peter Zijlstra
2014-02-07 17:19 ` Peter Zijlstra
2014-02-07 15:51 ` Kumar Gala
2014-02-07 15:51 ` Kumar Gala
2014-02-07 16:10 ` Peter Zijlstra
2014-02-07 16:10 ` Peter Zijlstra
2014-02-10 3:05 ` Benjamin Herrenschmidt
2014-02-10 3:05 ` Benjamin Herrenschmidt
2014-02-10 3:02 ` Benjamin Herrenschmidt
2014-02-10 3:02 ` Benjamin Herrenschmidt
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