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    Subject[RFC PATCH 6/6] 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 | 6 +++---
    2 files changed, 11 insertions(+), 9 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 6ad61fb..e41e29b 100644
    --- a/kernel/perf_event.c
    +++ b/kernel/perf_event.c
    @@ -1767,7 +1767,7 @@ static u64 perf_event_read(struct perf_event *event)
    * Callchain support
    */

    -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);
    static struct perf_callchain_entry **callchain_cpu_entries;
    @@ -1812,8 +1812,8 @@ static int alloc_callchain_buffers(void)
    callchain_cpu_entries = entries;

    for_each_possible_cpu(cpu) {
    - entries[cpu] = kmalloc(sizeof(struct perf_callchain_entry) * 4,
    - GFP_KERNEL);
    + entries[cpu] = kmalloc(sizeof(struct perf_callchain_entry) *
    + PERF_NR_CONTEXTS, GFP_KERNEL);
    if (!entries[cpu])
    return -ENOMEM;
    }
    --
    1.6.2.3


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