From: Eric Dumazet <eric.dumazet@gmail.com>
To: Peter Zijlstra <peterz@infradead.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>,
Ingo Molnar <mingo@kernel.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 06:21:31 -0800 [thread overview]
Message-ID: <1361542891.3683.6.camel@edumazet-glaptop> (raw)
In-Reply-To: <1361542150.26780.64.camel@laptop>
On Fri, 2013-02-22 at 15:09 +0100, Peter Zijlstra wrote:
> On Fri, 2013-02-22 at 13:50 +0100, Frederic Weisbecker wrote:
> > > Argh!! at what cost? 64bit atomics are like expensive. Wouldn't
> > adding
> > > a seqlock be saner?
> >
> > Not sure. This requires a spinlock in the write side which is called
> > from
> > fast path like the timer interrupt.
>
> A single spinlock is _way_ cheaper than a ton of cmpxchg8b()s to update
> a few variables.
We also have include/linux/u64_stats_sync.h since 2.6.36
WARNING: multiple messages have this Message-ID (diff)
From: eric.dumazet@gmail.com (Eric Dumazet)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/2] cpustat: use atomic operations to read/update stats
Date: Fri, 22 Feb 2013 06:21:31 -0800 [thread overview]
Message-ID: <1361542891.3683.6.camel@edumazet-glaptop> (raw)
In-Reply-To: <1361542150.26780.64.camel@laptop>
On Fri, 2013-02-22 at 15:09 +0100, Peter Zijlstra wrote:
> On Fri, 2013-02-22 at 13:50 +0100, Frederic Weisbecker wrote:
> > > Argh!! at what cost? 64bit atomics are like expensive. Wouldn't
> > adding
> > > a seqlock be saner?
> >
> > Not sure. This requires a spinlock in the write side which is called
> > from
> > fast path like the timer interrupt.
>
> A single spinlock is _way_ cheaper than a ton of cmpxchg8b()s to update
> a few variables.
We also have include/linux/u64_stats_sync.h since 2.6.36
next prev parent reply other threads:[~2013-02-22 14:21 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
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 [this message]
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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