From: Avi Kivity <avi@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: akpm@linux-foundation.org, Paul Mackerras <paulus@samba.org>,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 1/2] lib: Provide generic atomic64_t implementation
Date: Sun, 14 Jun 2009 14:53:09 +0300 [thread overview]
Message-ID: <4A34E4A5.3040306@redhat.com> (raw)
In-Reply-To: <alpine.LFD.2.01.0906131323270.3237@localhost.localdomain>
Linus Torvalds wrote:
> On Sat, 13 Jun 2009, Linus Torvalds wrote:
>
>> On Sat, 13 Jun 2009, Paul Mackerras wrote:
>>
>>> Linus, Andrew: OK if this goes in via the powerpc tree?
>>>
>> Ok by me.
>>
>
> Btw, do 32-bit architectures really necessarily want 64-bit performance
> counters?
>
> I realize that 32-bit counters will overflow pretty easily, but I do
> wonder about the performance impact of doing things like hashed spinlocks
> for 64-bit counters. Maybe the downsides of 64-bit perf counters on such
> architectures might outweight the upsides?
>
An alternative implementation using 64-bit cmpxchg will recover most of
the costs of hashed spinlocks. I assume most serious 32-bit
architectures have them?
--
error compiling committee.c: too many arguments to function
WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>,
benh@kernel.crashing.org, akpm@linux-foundation.org,
linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] lib: Provide generic atomic64_t implementation
Date: Sun, 14 Jun 2009 14:53:09 +0300 [thread overview]
Message-ID: <4A34E4A5.3040306@redhat.com> (raw)
In-Reply-To: <alpine.LFD.2.01.0906131323270.3237@localhost.localdomain>
Linus Torvalds wrote:
> On Sat, 13 Jun 2009, Linus Torvalds wrote:
>
>> On Sat, 13 Jun 2009, Paul Mackerras wrote:
>>
>>> Linus, Andrew: OK if this goes in via the powerpc tree?
>>>
>> Ok by me.
>>
>
> Btw, do 32-bit architectures really necessarily want 64-bit performance
> counters?
>
> I realize that 32-bit counters will overflow pretty easily, but I do
> wonder about the performance impact of doing things like hashed spinlocks
> for 64-bit counters. Maybe the downsides of 64-bit perf counters on such
> architectures might outweight the upsides?
>
An alternative implementation using 64-bit cmpxchg will recover most of
the costs of hashed spinlocks. I assume most serious 32-bit
architectures have them?
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2009-06-14 11:53 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-13 7:10 [PATCH 1/2] lib: Provide generic atomic64_t implementation Paul Mackerras
2009-06-13 7:10 ` Paul Mackerras
2009-06-13 20:13 ` Linus Torvalds
2009-06-13 20:13 ` Linus Torvalds
2009-06-13 20:25 ` Linus Torvalds
2009-06-13 20:25 ` Linus Torvalds
2009-06-13 20:56 ` Ingo Molnar
2009-06-13 20:56 ` Ingo Molnar
2009-06-14 11:53 ` Avi Kivity [this message]
2009-06-14 11:53 ` Avi Kivity
2009-06-14 12:21 ` Paul Mackerras
2009-06-14 12:21 ` Paul Mackerras
2009-06-14 13:04 ` Avi Kivity
2009-06-14 13:04 ` Avi Kivity
2009-06-15 2:44 ` Roland Dreier
2009-06-15 2:44 ` Roland Dreier
2009-06-15 4:30 ` Paul Mackerras
2009-06-15 4:30 ` Paul Mackerras
2009-06-16 22:27 ` Gabriel Paubert
2009-06-16 22:27 ` Gabriel Paubert
2009-06-13 21:53 ` Arnd Bergmann
2009-06-13 21:53 ` Arnd Bergmann
2009-06-18 23:55 ` Mike Frysinger
2009-06-18 23:55 ` Mike Frysinger
2009-06-19 0:46 ` Benjamin Herrenschmidt
2009-06-19 0:46 ` Benjamin Herrenschmidt
2009-06-19 0:47 ` Paul Mackerras
2009-06-19 0:47 ` Paul Mackerras
2009-06-19 0:49 ` Mike Frysinger
2009-06-19 0:49 ` Mike Frysinger
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