From: Christoph Lameter <cl@linux.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: akpm@linux-foundation.org, Pekka Enberg <penberg@cs.helsinki.fi>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
linux-kernel@vger.kernel.org,
Eric Dumazet <eric.dumazet@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Tejun Heo <tj@kernel.org>,
linux-mm@kvack.org
Subject: Re: [thisops uV3 15/18] Xen: Use this_cpu_ops
Date: Tue, 30 Nov 2010 15:03:20 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.00.1011301501320.4039@router.home> (raw)
In-Reply-To: <4CF56463.3040109@goop.org>
On Tue, 30 Nov 2010, Jeremy Fitzhardinge wrote:
> On 11/30/2010 11:07 AM, Christoph Lameter wrote:
> > static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
> > {
> > - struct clock_event_device *evt = &__get_cpu_var(xen_clock_events);
> > irqreturn_t ret;
> >
> > ret = IRQ_NONE;
> > - if (evt->event_handler) {
> > - evt->event_handler(evt);
> > + if (__this_cpu_read(xen_clock_events.event_handler)) {
> > + __this_cpu_read(xen_clock_events.event_handler)(evt);
>
> Really? What code does this generate? If this is generating two
> segment-prefixed reads rather than getting the address and doing normal
> reads on it, then I don't think it is an improvement.
Lets drop that hunk. No point to do optimizations at that location then.
evt is also not defined then. Without the evt address determination via
__get_cpu_var we have at least 2 prefixed load and one address
calculation to figure out the parameter to pass. No win.
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next prev parent reply other threads:[~2010-11-30 21:03 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-30 19:07 [thisops uV3 00/18] Upgrade of this_cpu_ops V3 Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 01/18] percpucounter: Optimize __percpu_counter_add a bit through the use of this_cpu() options Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 02/18] vmstat: Optimize zone counter modifications through the use of this cpu operations Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 03/18] percpu: Generic support for this_cpu_add,sub,dec,inc_return Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 04/18] x86: Support " Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 05/18] x86: Use this_cpu_inc_return for nmi counter Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 06/18] vmstat: Use this_cpu_inc_return for vm statistics Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 07/18] highmem: Use this_cpu_xx_return() operations Christoph Lameter
2010-11-30 19:13 ` Eric Dumazet
2010-11-30 19:19 ` Peter Zijlstra
2010-11-30 19:26 ` Christoph Lameter
2010-11-30 19:29 ` Eric Dumazet
2010-11-30 19:38 ` Peter Zijlstra
2010-11-30 19:53 ` Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 08/18] Taskstats: Use this_cpu_ops Christoph Lameter
2010-12-01 18:06 ` Michael Holzheu
2010-12-01 18:13 ` Christoph Lameter
2010-12-06 14:32 ` Balbir Singh
2010-12-07 14:39 ` Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 09/18] fs: Use this_cpu_xx operations in buffer.c Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 10/18] x86: Use this_cpu_ops to optimize code Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 11/18] x86: Use this_cpu_ops for current_cpu_data accesses Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 12/18] Core: Replace __get_cpu_var with __this_cpu_read if not used for an address Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 13/18] drivers: " Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 14/18] lguest: Use this_cpu_ops Christoph Lameter
2010-12-06 7:46 ` Rusty Russell
2010-12-06 15:54 ` Christoph Lameter
2010-12-06 16:27 ` Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 15/18] Xen: " Christoph Lameter
2010-11-30 20:53 ` Jeremy Fitzhardinge
2010-11-30 21:03 ` Christoph Lameter [this message]
2010-11-30 19:07 ` [thisops uV3 16/18] kprobes: " Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 17/18] Connector: Use this_cpu operations Christoph Lameter
2010-11-30 19:07 ` [thisops uV3 18/18] Fakekey: Simplify speakup_fake_key_pressed through this_cpu_ops Christoph Lameter
2010-11-30 20:05 ` [extra] timers: Use this_cpu_read Christoph Lameter
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