linux-kernel - Re: [PATCH v2 05/12] perf/x86: add cross-HT counter exclusion infrastructure

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Date:	Thu, 23 Oct 2014 09:14:49 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"Liang, Kan" <kan.liang@...el.com>, Borislav Petkov <bp@...en8.de>,
	Maria Dimakopoulou <maria.n.dimakopoulou@...il.com>
Subject: Re: [PATCH v2 05/12] perf/x86: add cross-HT counter exclusion
 infrastructure

On Wed, Oct 22, 2014 at 07:25:40PM +0200, Stephane Eranian wrote:
> On Wed, Oct 22, 2014 at 5:07 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> > On Thu, Oct 09, 2014 at 06:34:39PM +0200, Stephane Eranian wrote:
> >> From: Maria Dimakopoulou <maria.n.dimakopoulou@...il.com>
> >>
> >
> > SNIP
> >
> >> +struct intel_excl_cntrs *allocate_excl_cntrs(int cpu)
> >> +{
> >> +     struct intel_excl_cntrs *c;
> >> +     int i;
> >> +
> >> +     c = kzalloc_node(sizeof(struct intel_excl_cntrs),
> >> +                      GFP_KERNEL, cpu_to_node(cpu));
> >> +     if (c) {
> >> +             spin_lock_init(&c->lock);
> >> +             for (i = 0; i < X86_PMC_IDX_MAX; i++) {
> >> +                     c->states[0].state[i] = INTEL_EXCL_UNUSED;
> >> +                     c->states[0].init_state[i] = INTEL_EXCL_UNUSED;
> >> +
> >> +                     c->states[1].state[i] = INTEL_EXCL_UNUSED;
> >> +                     c->states[1].init_state[i] = INTEL_EXCL_UNUSED;
> >
> > 'c' is allocated with kzalloc_node, seems there's no need
> > to re-initialize states it to zero again with INTEL_EXCL_UNUSED
> >
> You are assuming that INTEL_EXCL_UNUSED=0 always.
> That means it needs to be clear there is a dependency here.

it's 0 explicitly:

enum intel_excl_state_type {
        INTEL_EXCL_UNUSED    = 0, /* counter is unused */

but it's not big issue for me.. just curious ;-)

jirka
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