Re: [PATCH 4/9] perf/x86: add cross-HT counter exclusion infrastructure

Peter Zijlstra
2014-06-05T07:47:58Z

[-- Attachment #1: Type: text/plain, Size: 2886 bytes --]

On Wed, Jun 04, 2014 at 11:34:13PM +0200, Stephane Eranian wrote:
> From: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
>
> This patch adds a new shared_regs style structure to the
> per-cpu x86 state (cpuc). It is used to coordinate access
> between counters which must be used with exclusion across
> HyperThreads on Intel processors. This new struct is not
> needed on each PMU, thus is is allocated on demand.
>
> Reviewed-by: Stephane Eranian <eranian@google.com>
> Signed-off-by: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
> ---
> arch/x86/kernel/cpu/perf_event.h | 40 ++++++++++++++++++--
> arch/x86/kernel/cpu/perf_event_intel.c | 63 +++++++++++++++++++++++++++++---
> 2 files changed, 94 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
> index 413799f..5da0a2b 100644
> --- a/arch/x86/kernel/cpu/perf_event.h
> +++ b/arch/x86/kernel/cpu/perf_event.h
> @@ -65,10 +65,11 @@ struct event_constraint {
> /*
> * struct hw_perf_event.flags flags
> */
> -#define PERF_X86_EVENT_PEBS_LDLAT 0x1 /* ld+ldlat data address sampling */
> -#define PERF_X86_EVENT_PEBS_ST 0x2 /* st data address sampling */
> -#define PERF_X86_EVENT_PEBS_ST_HSW 0x4 /* haswell style st data sampling */
> -#define PERF_X86_EVENT_COMMITTED 0x8 /* event passed commit_txn */
> +#define PERF_X86_EVENT_PEBS_LDLAT 0x01 /* ld+ldlat data address sampling */
> +#define PERF_X86_EVENT_PEBS_ST 0x02 /* st data address sampling */
> +#define PERF_X86_EVENT_PEBS_ST_HSW 0x04 /* haswell style st data sampling */
> +#define PERF_X86_EVENT_COMMITTED 0x08 /* event passed commit_txn */
> +#define PERF_X86_EVENT_EXCL 0x10 /* HT exclusivity on counter */
>
> struct amd_nb {
> int nb_id; /* NorthBridge id */
> @@ -119,6 +120,27 @@ struct intel_shared_regs {
> unsigned core_id; /* per-core: core id */
> };
>
> +enum intel_excl_state_type {
> + INTEL_EXCL_UNUSED = 0, /* counter is unused */
> + INTEL_EXCL_SHARED = 1, /* counter can be used by both threads */
> + INTEL_EXCL_EXCLUSIVE = 2, /* counter can be used by one thread only */
> +};
> +
> +struct intel_excl_states {
> + enum intel_excl_state_type init_state[X86_PMC_IDX_MAX];
> + enum intel_excl_state_type state[X86_PMC_IDX_MAX];
> +};
> +
> +struct intel_excl_cntrs {
> + spinlock_t lock;
> + unsigned long lock_flags;
> +
> + struct intel_excl_states states[2];
> +
> + int refcnt; /* per-core: #HT threads */
> + unsigned core_id; /* per-core: core id */
> +};

This must be a raw_spin_lock_t, its taken from pmu::add() which is
called under perf_event_context::lock, which is raw_spinlock_t, as its
taken under rq::lock, which too is raw_spinlock_t.

I should really get around to fixing these errors and include the
lockdep infrastructure for this.

[-- Attachment #2: Type: application/pgp-signature, Size: 836 bytes --]