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Date: Fri, 1 Feb 2013 18:18:41 +0100
From: Stephane Eranian <eranian@...gle.com>
To: Andi Kleen <andi@...stfloor.org>
Cc: Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andrew Morton <akpm@...ux-foundation.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 01/12] perf, x86: Add PEBSv2 record support
On Thu, Jan 31, 2013 at 11:51 PM, Andi Kleen <andi@...stfloor.org> wrote:
> From: Andi Kleen <ak@...ux.intel.com>
>
> Add support for the v2 PEBS format. It has a superset of the v1 PEBS
> fields, but has a longer record so we need to adjust the code paths.
>
> The main advantage is the new "EventingRip" support which directly
> gives the instruction, not off-by-one instruction. So with precise == 2
> we use that directly and don't try to use LBRs and walking basic blocks.
> This lowers the overhead significantly.
>
> Some other features are added in later patches.
>
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Stephane Eranian <eranian@...gle.com>
> ---
> arch/x86/kernel/cpu/perf_event.c | 2 +-
> arch/x86/kernel/cpu/perf_event_intel_ds.c | 101 ++++++++++++++++++++++-------
> 2 files changed, 79 insertions(+), 24 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> index 6774c17..c95290a 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -397,7 +397,7 @@ int x86_pmu_hw_config(struct perf_event *event)
> * check that PEBS LBR correction does not conflict with
> * whatever the user is asking with attr->branch_sample_type
> */
> - if (event->attr.precise_ip > 1) {
> + if (event->attr.precise_ip > 1 && x86_pmu.intel_cap.pebs_format < 2) {
> u64 *br_type = &event->attr.branch_sample_type;
>
> if (has_branch_stack(event)) {
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> index 826054a..9d0dae0 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> @@ -41,6 +41,12 @@ struct pebs_record_nhm {
> u64 status, dla, dse, lat;
> };
>
> +struct pebs_record_v2 {
> + struct pebs_record_nhm nhm;
> + u64 eventingrip;
> + u64 tsx_tuning;
> +};
> +
> void init_debug_store_on_cpu(int cpu)
> {
> struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds;
> @@ -559,8 +565,7 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
> {
> /*
> * We cast to pebs_record_core since that is a subset of
> - * both formats and we don't use the other fields in this
> - * routine.
> + * both formats.
> */
> struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> struct pebs_record_core *pebs = __pebs;
> @@ -588,7 +593,10 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
> regs.bp = pebs->bp;
> regs.sp = pebs->sp;
>
> - if (event->attr.precise_ip > 1 && intel_pmu_pebs_fixup_ip(®s))
> + if (event->attr.precise_ip > 1 && x86_pmu.intel_cap.pebs_format >= 2) {
> + regs.ip = ((struct pebs_record_v2 *)pebs)->eventingrip;
> + regs.flags |= PERF_EFLAGS_EXACT;
> + } else if (event->attr.precise_ip > 1 && intel_pmu_pebs_fixup_ip(®s))
> regs.flags |= PERF_EFLAGS_EXACT;
> else
> regs.flags &= ~PERF_EFLAGS_EXACT;
> @@ -641,35 +649,21 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
> __intel_pmu_pebs_event(event, iregs, at);
> }
>
> -static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
> +static void intel_pmu_drain_pebs_common(struct pt_regs *iregs, void *at,
> + void *top)
> {
> struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> struct debug_store *ds = cpuc->ds;
> - struct pebs_record_nhm *at, *top;
> struct perf_event *event = NULL;
> u64 status = 0;
> - int bit, n;
> -
> - if (!x86_pmu.pebs_active)
> - return;
> -
> - at = (struct pebs_record_nhm *)(unsigned long)ds->pebs_buffer_base;
> - top = (struct pebs_record_nhm *)(unsigned long)ds->pebs_index;
> + int bit;
>
> ds->pebs_index = ds->pebs_buffer_base;
>
> - n = top - at;
> - if (n <= 0)
> - return;
> + for ( ; at < top; at += x86_pmu.pebs_record_size) {
> + struct pebs_record_nhm *p = at;
>
> - /*
> - * Should not happen, we program the threshold at 1 and do not
> - * set a reset value.
> - */
> - WARN_ONCE(n > x86_pmu.max_pebs_events, "Unexpected number of pebs records %d\n", n);
> -
> - for ( ; at < top; at++) {
> - for_each_set_bit(bit, (unsigned long *)&at->status, x86_pmu.max_pebs_events) {
> + for_each_set_bit(bit, (unsigned long *)&p->status, x86_pmu.max_pebs_events) {
> event = cpuc->events[bit];
> if (!test_bit(bit, cpuc->active_mask))
> continue;
> @@ -692,6 +686,61 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
> }
> }
>
> +static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
> +{
> + struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> + struct debug_store *ds = cpuc->ds;
> + struct pebs_record_nhm *at, *top;
> + int n;
> +
> + if (!x86_pmu.pebs_active)
> + return;
> +
> + at = (struct pebs_record_nhm *)(unsigned long)ds->pebs_buffer_base;
> + top = (struct pebs_record_nhm *)(unsigned long)ds->pebs_index;
> +
> + ds->pebs_index = ds->pebs_buffer_base;
> +
> + n = top - at;
> + if (n <= 0)
> + return;
> +
> + /*
> + * Should not happen, we program the threshold at 1 and do not
> + * set a reset value.
> + */
> + WARN_ONCE(n > x86_pmu.max_pebs_events,
> + "Unexpected number of pebs records %d\n", n);
> +
> + return intel_pmu_drain_pebs_common(iregs, at, top);
> +}
> +
> +static void intel_pmu_drain_pebs_v2(struct pt_regs *iregs)
> +{
> + struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> + struct debug_store *ds = cpuc->ds;
> + struct pebs_record_v2 *at, *top;
> + int n;
> +
> + if (!x86_pmu.pebs_active)
> + return;
> +
> + at = (struct pebs_record_v2 *)(unsigned long)ds->pebs_buffer_base;
> + top = (struct pebs_record_v2 *)(unsigned long)ds->pebs_index;
> +
> + n = top - at;
> + if (n <= 0)
> + return;
> + /*
> + * Should not happen, we program the threshold at 1 and do not
> + * set a reset value.
> + */
> + WARN_ONCE(n > x86_pmu.max_pebs_events,
> + "Unexpected number of pebs records %d\n", n);
> +
> + return intel_pmu_drain_pebs_common(iregs, at, top);
> +}
> +
> /*
> * BTS, PEBS probe and setup
> */
> @@ -723,6 +772,12 @@ void intel_ds_init(void)
> x86_pmu.drain_pebs = intel_pmu_drain_pebs_nhm;
> break;
>
> + case 2:
> + printk(KERN_CONT "PEBS fmt2%c, ", pebs_type);
> + x86_pmu.pebs_record_size = sizeof(struct pebs_record_v2);
> + x86_pmu.drain_pebs = intel_pmu_drain_pebs_v2;
> + break;
> +
> default:
> printk(KERN_CONT "no PEBS fmt%d%c, ", format, pebs_type);
> x86_pmu.pebs = 0;
> --
> 1.7.7.6
>
--
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