From: Matt Mackall <mpm@selenic.com>
To: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>,
akpm@linux-foundation.org,
Richard Kennedy <richard@rsk.demon.co.uk>,
Pekka Enberg <penberg@cs.helsinki.fi>,
linux-kernel@vger.kernel.org,
Eric Dumazet <eric.dumazet@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [cpuops inc_return V1 8/9] random: Use this_cpu_inc_return
Date: Mon, 06 Dec 2010 12:11:42 -0600 [thread overview]
Message-ID: <1291659102.3065.2212.camel@calx> (raw)
In-Reply-To: <20101206174017.684979312@linux.com>
On Mon, 2010-12-06 at 11:40 -0600, Christoph Lameter wrote:
> plain text document attachment (cpuops_inc_return_random)
> __this_cpu_inc can create a single instruction to do the same as
> __get_cpu_var()++.
> - (__get_cpu_var(trickle_count)++ & 0xfff))
> + ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
I see you've added a "- 1" to mimic the post-increment ++ semantic.
The goal of this code to add only 1 sample in every 4096, but we don't
really care which, so this semantic isn't actually important here.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2010-12-06 18:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-06 17:39 [cpuops inc_return V1 0/9] Implement this_cpu_inc_return (and friends) and use it in various places Christoph Lameter
2010-12-06 17:39 ` [cpuops inc_return V1 1/9] percpu: Generic support for this_cpu_add,sub,dec,inc_return Christoph Lameter
2010-12-08 16:15 ` [cpuops UPDATED " Tejun Heo
2010-12-06 17:40 ` [cpuops inc_return V1 2/9] x86: Support " Christoph Lameter
2010-12-08 16:44 ` [cpuops UPDATED 2/9] x86: Support for this_cpu_add, sub, dec, inc_return Tejun Heo
2010-12-06 17:40 ` [cpuops inc_return V1 3/9] x86: Use this_cpu_inc_return for nmi counter Christoph Lameter
2010-12-08 16:45 ` Tejun Heo
2010-12-08 17:31 ` Christoph Lameter
2010-12-08 17:45 ` Tejun Heo
2010-12-06 17:40 ` [cpuops inc_return V1 4/9] vmstat: Use this_cpu_inc_return for vm statistics Christoph Lameter
2010-12-06 17:40 ` [cpuops inc_return V1 5/9] highmem: Use this_cpu_xx_return() operations Christoph Lameter
2010-12-06 17:40 ` [cpuops inc_return V1 6/9] Taskstats: Use this_cpu_ops Christoph Lameter
2010-12-07 9:35 ` Michael Holzheu
2010-12-07 14:45 ` Christoph Lameter
2010-12-06 17:40 ` [cpuops inc_return V1 7/9] fs: Use this_cpu_inc_return in buffer.c Christoph Lameter
2010-12-06 17:40 ` [cpuops inc_return V1 8/9] random: Use this_cpu_inc_return Christoph Lameter
2010-12-06 18:11 ` Matt Mackall [this message]
2010-12-06 18:29 ` Christoph Lameter
2010-12-06 17:40 ` [cpuops inc_return V1 9/9] Xen: " Christoph Lameter
2010-12-07 15:46 ` Straggler: Connector: Use this_cpu_operations Christoph Lameter
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