From: peterz@infradead.org (Peter Zijlstra)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/2] cpustat: use atomic operations to read/update stats
Date: Fri, 22 Feb 2013 15:25:28 +0100 [thread overview]
Message-ID: <1361543128.26780.65.camel@laptop> (raw)
In-Reply-To: <20130222141635.GA9606@gmail.com>
On Fri, 2013-02-22 at 15:16 +0100, Ingo Molnar wrote:
> > I checked arch/x86/include/asm/atomic64_32.h and we use
> > cmpxchg8b for everything from _set() to _read(), which
> > translates into 'horridly stupendifyingly slow' for a number
> > of machines, but coherent.
>
> That's a valid concern - and cmpxchg8b is the only 64-bit op
> available on most 32-bit x86 CPUs which does not involve the
> FPU.
>
> Wondering how significant this range of x86 problem boxes will
> be by the time any of these changes reaches upstream and distros
> - and how much 'horridly stupendifyingly slow' is in terms of
> cycles expended.
On the !x86 side of things we're implementing (generic) atomic64 using
hashed spinlocks, so there too using a single spinlock around the
entire data structure is a complete win.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Kevin Hilman <khilman@linaro.org>,
Russell King <rmk+kernel@arm.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linaro-kernel@lists.linaro.org
Subject: Re: [PATCH 0/2] cpustat: use atomic operations to read/update stats
Date: Fri, 22 Feb 2013 15:25:28 +0100 [thread overview]
Message-ID: <1361543128.26780.65.camel@laptop> (raw)
In-Reply-To: <20130222141635.GA9606@gmail.com>
On Fri, 2013-02-22 at 15:16 +0100, Ingo Molnar wrote:
> > I checked arch/x86/include/asm/atomic64_32.h and we use
> > cmpxchg8b for everything from _set() to _read(), which
> > translates into 'horridly stupendifyingly slow' for a number
> > of machines, but coherent.
>
> That's a valid concern - and cmpxchg8b is the only 64-bit op
> available on most 32-bit x86 CPUs which does not involve the
> FPU.
>
> Wondering how significant this range of x86 problem boxes will
> be by the time any of these changes reaches upstream and distros
> - and how much 'horridly stupendifyingly slow' is in terms of
> cycles expended.
On the !x86 side of things we're implementing (generic) atomic64 using
hashed spinlocks, so there too using a single spinlock around the
entire data structure is a complete win.
next prev parent reply other threads:[~2013-02-22 14:25 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-22 5:56 [PATCH 0/2] cpustat: use atomic operations to read/update stats Kevin Hilman
2013-02-22 5:56 ` Kevin Hilman
2013-02-22 5:56 ` [PATCH 1/2] cpustat: use accessor functions for get/set/add Kevin Hilman
2013-02-22 5:56 ` Kevin Hilman
2013-02-22 6:21 ` Viresh Kumar
2013-02-22 6:21 ` Viresh Kumar
2013-02-22 7:17 ` Amit Kucheria
2013-02-22 7:17 ` Amit Kucheria
2013-02-22 7:50 ` Viresh Kumar
2013-02-22 7:50 ` Viresh Kumar
2013-02-22 12:34 ` Frederic Weisbecker
2013-02-22 12:34 ` Frederic Weisbecker
2013-02-22 15:14 ` Kevin Hilman
2013-02-22 15:14 ` Kevin Hilman
2013-02-22 13:38 ` Frederic Weisbecker
2013-02-22 13:38 ` Frederic Weisbecker
2013-02-22 13:58 ` Peter Zijlstra
2013-02-22 13:58 ` Peter Zijlstra
2013-02-22 14:03 ` Frederic Weisbecker
2013-02-22 14:03 ` Frederic Weisbecker
2013-02-22 5:56 ` [PATCH 2/2] cpustat: convert to atomic operations Kevin Hilman
2013-02-22 5:56 ` Kevin Hilman
2013-02-22 8:46 ` [PATCH 0/2] cpustat: use atomic operations to read/update stats Peter Zijlstra
2013-02-22 8:46 ` Peter Zijlstra
2013-02-22 12:50 ` Frederic Weisbecker
2013-02-22 12:50 ` Frederic Weisbecker
2013-02-22 13:48 ` Peter Zijlstra
2013-02-22 13:48 ` Peter Zijlstra
2013-02-22 13:54 ` Ingo Molnar
2013-02-22 13:54 ` Ingo Molnar
2013-02-22 14:04 ` Peter Zijlstra
2013-02-22 14:04 ` Peter Zijlstra
2013-02-22 14:16 ` Ingo Molnar
2013-02-22 14:16 ` Ingo Molnar
2013-02-22 14:25 ` Peter Zijlstra [this message]
2013-02-22 14:25 ` Peter Zijlstra
2013-02-22 14:05 ` Peter Zijlstra
2013-02-22 14:05 ` Peter Zijlstra
2013-02-22 14:15 ` Frederic Weisbecker
2013-02-22 14:15 ` Frederic Weisbecker
2013-02-22 14:09 ` Peter Zijlstra
2013-02-22 14:09 ` Peter Zijlstra
2013-02-22 14:18 ` Ingo Molnar
2013-02-22 14:18 ` Ingo Molnar
2013-02-22 14:21 ` Eric Dumazet
2013-02-22 14:21 ` Eric Dumazet
2013-02-22 14:23 ` Frederic Weisbecker
2013-02-22 14:23 ` Frederic Weisbecker
2013-02-22 19:01 ` Kevin Hilman
2013-02-22 19:01 ` Kevin Hilman
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