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    Subject[PATCH 6/7] perf: Humanize the number of contexts
    Date
    Instead of hardcoding the number of contexts for the recursions
    barriers, define a cpp constant to make the code more
    self-explanatory.

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Stephane Eranian <eranian@google.com>
    ---
    include/linux/perf_event.h | 14 ++++++++------
    kernel/perf_event.c | 4 ++--
    kernel/trace/trace_event_perf.c | 8 ++++----
    3 files changed, 14 insertions(+), 12 deletions(-)

    diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
    index d7e8ea6..ae6fa60 100644
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -808,6 +808,12 @@ struct perf_event_context {
    struct rcu_head rcu_head;
    };

    +/*
    + * Number of contexts where an event can trigger:
    + * task, softirq, hardirq, nmi.
    + */
    +#define PERF_NR_CONTEXTS 4
    +
    /**
    * struct perf_event_cpu_context - per cpu event context structure
    */
    @@ -821,12 +827,8 @@ struct perf_cpu_context {
    struct mutex hlist_mutex;
    int hlist_refcount;

    - /*
    - * Recursion avoidance:
    - *
    - * task, softirq, irq, nmi context
    - */
    - int recursion[4];
    + /* Recursion avoidance in each contexts */
    + int recursion[PERF_NR_CONTEXTS];
    };

    struct perf_output_handle {
    diff --git a/kernel/perf_event.c b/kernel/perf_event.c
    index 75ab8a2..f416aef 100644
    --- a/kernel/perf_event.c
    +++ b/kernel/perf_event.c
    @@ -1772,7 +1772,7 @@ struct callchain_cpus_entries {
    struct perf_callchain_entry *cpu_entries[0];
    };

    -static DEFINE_PER_CPU(int, callchain_recursion[4]);
    +static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
    static atomic_t nr_callchain_events;
    static DEFINE_MUTEX(callchain_mutex);
    struct callchain_cpus_entries *callchain_cpus_entries;
    @@ -1828,7 +1828,7 @@ static int alloc_callchain_buffers(void)
    if (!entries)
    return -ENOMEM;

    - size = sizeof(struct perf_callchain_entry) * 4;
    + size = sizeof(struct perf_callchain_entry) * PERF_NR_CONTEXTS;

    for_each_possible_cpu(cpu) {
    entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
    diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
    index 000e6e8..db2eae2 100644
    --- a/kernel/trace/trace_event_perf.c
    +++ b/kernel/trace/trace_event_perf.c
    @@ -9,7 +9,7 @@
    #include <linux/kprobes.h>
    #include "trace.h"

    -static char *perf_trace_buf[4];
    +static char *perf_trace_buf[PERF_NR_CONTEXTS];

    /*
    * Force it to be aligned to unsigned long to avoid misaligned accesses
    @@ -45,7 +45,7 @@ static int perf_trace_event_init(struct ftrace_event_call *tp_event,
    char *buf;
    int i;

    - for (i = 0; i < 4; i++) {
    + for (i = 0; i < PERF_NR_CONTEXTS; i++) {
    buf = (char *)alloc_percpu(perf_trace_t);
    if (!buf)
    goto fail;
    @@ -65,7 +65,7 @@ fail:
    if (!total_ref_count) {
    int i;

    - for (i = 0; i < 4; i++) {
    + for (i = 0; i < PERF_NR_CONTEXTS; i++) {
    free_percpu(perf_trace_buf[i]);
    perf_trace_buf[i] = NULL;
    }
    @@ -140,7 +140,7 @@ void perf_trace_destroy(struct perf_event *p_event)
    tp_event->perf_events = NULL;

    if (!--total_ref_count) {
    - for (i = 0; i < 4; i++) {
    + for (i = 0; i < PERF_NR_CONTEXTS; i++) {
    free_percpu(perf_trace_buf[i]);
    perf_trace_buf[i] = NULL;
    }
    --
    1.6.2.3


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