From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"mingo@elte.hu" <mingo@elte.hu>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"Yan, Zheng" <zheng.z.yan@intel.com>,
Robert Richter <robert.richter@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH v2 1/3] hrtimer: add hrtimer_init_cpu()
Date: Wed, 12 Sep 2012 16:38:39 +0200 [thread overview]
Message-ID: <1347460719.15764.42.camel@twins> (raw)
In-Reply-To: <CABPqkBSnhjgAhn5+gOuBWWPrxKojKW1hKPJEn7zvvYhiw-LPLg@mail.gmail.com>
On Wed, 2012-09-12 at 16:33 +0200, Stephane Eranian wrote:
>
> If I do:
> for_each_possible_cpu(cpu) {
> cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
> hr = &cpuctx->hrtimer;
> hrtimer_init(hr)
> }
> I don't understand why I would have to refer to per-cpu data
> (hrtimer_bases) from
> a CPU that is not equal to "cpu" here. Unless you're telling me it's
> read-only data.
No its not read only, but it is unused until you do *hrtimer_start*(),
which will test and fix.
> But still if it's per-cpu why not initialize with the correct CPU from
> the start?
To keep the interface simpler I guess. There's no great harm in your
proposal, but it is strictly speaking superfluous. I'm not sure the max
one time avoidance of a base swizzle is worth the extra interface, I'll
leave that up to Thomas.
Also, what Eric said ;-)
next prev parent reply other threads:[~2012-09-12 14:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-12 14:13 [PATCH v2 0/3] perf: use hrtimer for event multiplexing Stephane Eranian
2012-09-12 14:13 ` [PATCH v2 1/3] hrtimer: add hrtimer_init_cpu() Stephane Eranian
2012-09-12 14:22 ` Eric Dumazet
2012-09-12 14:26 ` Peter Zijlstra
2012-09-12 14:33 ` Stephane Eranian
2012-09-12 14:38 ` Peter Zijlstra [this message]
2012-09-12 14:46 ` Stephane Eranian
2012-09-12 14:49 ` Peter Zijlstra
2012-09-12 14:51 ` Stephane Eranian
2012-09-12 14:13 ` [PATCH v2 2/3] perf: use hrtimer for event multiplexing Stephane Eranian
2012-09-12 14:22 ` Peter Zijlstra
2012-09-12 14:43 ` Stephane Eranian
2012-09-12 14:44 ` Peter Zijlstra
2012-09-12 14:48 ` Stephane Eranian
2012-09-12 14:50 ` Peter Zijlstra
2012-09-12 15:37 ` Stephane Eranian
2012-09-12 15:49 ` Stephane Eranian
2012-09-13 12:16 ` Peter Zijlstra
2012-09-13 12:20 ` Stephane Eranian
2012-09-13 12:26 ` Peter Zijlstra
2012-09-13 12:27 ` Stephane Eranian
2012-09-13 12:29 ` Peter Zijlstra
2012-09-12 14:13 ` [PATCH v2 3/3] perf: add sysfs entry to adjust multiplexing interval per PMU Stephane Eranian
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