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Date: Fri, 22 Jan 2010 17:08:11 +0100
From: Stephane Eranian <eranian@...gle.com>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: fweisbec@...il.com, paulus@...ba.org, mingo@...e.hu,
davem@...emloft.net, robert.richter@....com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] perf_event: Optimize the constraint searching bits
On Fri, Jan 22, 2010 at 4:50 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> Instead of copying bitmasks around, pass pointers to the constraint structure.
>
The reason I changed that is because of the AMD situation where constraints
are dynamically generated. So we need to get some storage from somwhere.
See my AMD NB patch,
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> LKML-Reference: <new-submission>
> ---
> arch/x86/kernel/cpu/perf_event.c | 81 ++++++++++++++++++---------------------
> 1 file changed, 38 insertions(+), 43 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/cpu/perf_event.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/cpu/perf_event.c
> +++ linux-2.6/arch/x86/kernel/cpu/perf_event.c
> @@ -135,12 +138,14 @@ struct x86_pmu {
> u64 intel_ctrl;
> void (*enable_bts)(u64 config);
> void (*disable_bts)(void);
> - void (*get_event_constraints)(struct cpu_hw_events *cpuc,
> - struct perf_event *event,
> - unsigned long *idxmsk);
> +
> + struct event_constraint *
> + (*get_event_constraints)(struct cpu_hw_events *cpuc,
> + struct perf_event *event);
> +
> void (*put_event_constraints)(struct cpu_hw_events *cpuc,
> struct perf_event *event);
> - const struct event_constraint *event_constraints;
> + struct event_constraint *event_constraints;
> };
>
> static struct x86_pmu x86_pmu __read_mostly;
> @@ -1244,18 +1249,16 @@ static inline int is_x86_event(struct pe
> static int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
> {
> int i, j , w, num;
> - int weight, wmax;
> - unsigned long *c;
> - unsigned long constraints[X86_PMC_IDX_MAX][BITS_TO_LONGS(X86_PMC_IDX_MAX)];
> + int weight, wmax;
> + struct event_constraint *c, *constraints[X86_PMC_IDX_MAX];
> unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
> struct hw_perf_event *hwc;
>
> bitmap_zero(used_mask, X86_PMC_IDX_MAX);
>
> for (i = 0; i < n; i++) {
> - x86_pmu.get_event_constraints(cpuc,
> - cpuc->event_list[i],
> - constraints[i]);
> + constraints[i] =
> + x86_pmu.get_event_constraints(cpuc, cpuc->event_list[i]);
> }
>
> /*
> @@ -1270,7 +1273,7 @@ static int x86_schedule_events(struct cp
> break;
>
> /* constraint still honored */
> - if (!test_bit(hwc->idx, c))
> + if (!test_bit(hwc->idx, c->idxmsk))
> break;
>
> /* not already used */
> @@ -1323,11 +1326,11 @@ static int x86_schedule_events(struct cp
> c = constraints[i];
> hwc = &cpuc->event_list[i]->hw;
>
> - weight = bitmap_weight(c, X86_PMC_IDX_MAX);
> + weight = bitmap_weight(c->idxmsk, X86_PMC_IDX_MAX);
> if (weight != w)
> continue;
>
> - for_each_bit(j, c, X86_PMC_IDX_MAX) {
> + for_each_bit(j, c->idxmsk, X86_PMC_IDX_MAX) {
> if (!test_bit(j, used_mask))
> break;
> }
> @@ -2165,11 +2167,13 @@ perf_event_nmi_handler(struct notifier_b
> return NOTIFY_STOP;
> }
>
> +static struct event_constraint unconstrained;
> +
> static struct event_constraint bts_constraint =
> EVENT_CONSTRAINT(0, 1ULL << X86_PMC_IDX_FIXED_BTS, 0);
>
> -static int intel_special_constraints(struct perf_event *event,
> - unsigned long *idxmsk)
> +static struct event_constraint *
> +intel_special_constraints(struct perf_event *event)
> {
> unsigned int hw_event;
>
> @@ -2179,46 +2183,34 @@ static int intel_special_constraints(str
> x86_pmu.event_map(PERF_COUNT_HW_BRANCH_INSTRUCTIONS)) &&
> (event->hw.sample_period == 1))) {
>
> - bitmap_copy((unsigned long *)idxmsk,
> - (unsigned long *)bts_constraint.idxmsk,
> - X86_PMC_IDX_MAX);
> - return 1;
> + return &bts_constraint;
> }
> - return 0;
> + return NULL;
> }
>
> -static void intel_get_event_constraints(struct cpu_hw_events *cpuc,
> - struct perf_event *event,
> - unsigned long *idxmsk)
> +static struct event_constraint *
> +intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
> {
> - const struct event_constraint *c;
> + struct event_constraint *c;
>
> - /*
> - * cleanup bitmask
> - */
> - bitmap_zero(idxmsk, X86_PMC_IDX_MAX);
> -
> - if (intel_special_constraints(event, idxmsk))
> - return;
> + c = intel_special_constraints(event);
> + if (c)
> + return c;
>
> if (x86_pmu.event_constraints) {
> for_each_event_constraint(c, x86_pmu.event_constraints) {
> - if ((event->hw.config & c->cmask) == c->code) {
> - bitmap_copy(idxmsk, c->idxmsk, X86_PMC_IDX_MAX);
> - return;
> - }
> + if ((event->hw.config & c->cmask) == c->code)
> + return c;
> }
> }
> - /* no constraints, means supports all generic counters */
> - bitmap_fill((unsigned long *)idxmsk, x86_pmu.num_events);
> +
> + return &unconstrained;
> }
>
> -static void amd_get_event_constraints(struct cpu_hw_events *cpuc,
> - struct perf_event *event,
> - unsigned long *idxmsk)
> +static struct event_constraint *
> +amd_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
> {
> - /* no constraints, means supports all generic counters */
> - bitmap_fill(idxmsk, x86_pmu.num_events);
> + return &unconstrained;
> }
>
> static int x86_event_sched_in(struct perf_event *event,
> @@ -2586,6 +2578,9 @@ void __init init_hw_perf_events(void)
> perf_events_lapic_init();
> register_die_notifier(&perf_event_nmi_notifier);
>
> + unconstrained = (struct event_constraint)
> + EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_events) - 1, 0);
> +
> pr_info("... version: %d\n", x86_pmu.version);
> pr_info("... bit width: %d\n", x86_pmu.event_bits);
> pr_info("... generic registers: %d\n", x86_pmu.num_events);
>
> --
>
>
--
Stephane Eranian | EMEA Software Engineering
Google France | 38 avenue de l'Opéra | 75002 Paris
Tel : +33 (0) 1 42 68 53 00
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