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    Subject[tip:perfcounters/core] perf_counter: provide generic callchain bits
    Commit-ID:  1254256f65ce3973462dc153e02b4f3a7e314e20
    Gitweb: http://git.kernel.org/tip/1254256f65ce3973462dc153e02b4f3a7e314e20
    Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    AuthorDate: Mon, 30 Mar 2009 19:07:14 +0200
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Wed, 1 Apr 2009 11:33:38 +0200

    perf_counter: provide generic callchain bits

    Provide the generic callchain support bits. If hw_event->callchain is
    set the arch specific perf_callchain() function is called upon to
    provide a perf_callchain_entry structure filled with the current
    callchain.

    If it does so, it is added to the overflow output event.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: Paul Mackerras <paulus@samba.org>
    LKML-Reference: <20090330171024.254266860@chello.nl>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>


    ---
    include/linux/perf_counter.h | 13 ++++++++++++-
    kernel/perf_counter.c | 27 +++++++++++++++++++++++++++
    2 files changed, 39 insertions(+), 1 deletions(-)

    diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
    index edf5bfb..43083af 100644
    --- a/include/linux/perf_counter.h
    +++ b/include/linux/perf_counter.h
    @@ -140,8 +140,9 @@ struct perf_counter_hw_event {
    include_tid : 1, /* include the tid */
    mmap : 1, /* include mmap data */
    munmap : 1, /* include munmap data */
    + callchain : 1, /* add callchain data */

    - __reserved_1 : 52;
    + __reserved_1 : 51;

    __u32 extra_config_len;
    __u32 __reserved_4;
    @@ -219,6 +220,7 @@ enum perf_event_type {
    PERF_EVENT_OVERFLOW = 1UL << 31,
    __PERF_EVENT_IP = 1UL << 30,
    __PERF_EVENT_TID = 1UL << 29,
    + __PERF_EVENT_CALLCHAIN = 1UL << 28,
    };

    #ifdef __KERNEL__
    @@ -504,6 +506,15 @@ extern void perf_counter_mmap(unsigned long addr, unsigned long len,
    extern void perf_counter_munmap(unsigned long addr, unsigned long len,
    unsigned long pgoff, struct file *file);

    +#define MAX_STACK_DEPTH 255
    +
    +struct perf_callchain_entry {
    + u64 nr;
    + u64 ip[MAX_STACK_DEPTH];
    +};
    +
    +extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
    +
    #else
    static inline void
    perf_counter_task_sched_in(struct task_struct *task, int cpu) { }
    diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
    index d93e9dd..860cdc2 100644
    --- a/kernel/perf_counter.c
    +++ b/kernel/perf_counter.c
    @@ -1654,6 +1654,17 @@ void perf_counter_do_pending(void)
    }

    /*
    + * Callchain support -- arch specific
    + */
    +
    +struct perf_callchain_entry *
    +__attribute__((weak))
    +perf_callchain(struct pt_regs *regs)
    +{
    + return NULL;
    +}
    +
    +/*
    * Output
    */

    @@ -1764,6 +1775,8 @@ static void perf_output_simple(struct perf_counter *counter,
    struct {
    u32 pid, tid;
    } tid_entry;
    + struct perf_callchain_entry *callchain = NULL;
    + int callchain_size = 0;

    header.type = PERF_EVENT_OVERFLOW;
    header.size = sizeof(header);
    @@ -1781,6 +1794,17 @@ static void perf_output_simple(struct perf_counter *counter,
    header.size += sizeof(tid_entry);
    }

    + if (counter->hw_event.callchain) {
    + callchain = perf_callchain(regs);
    +
    + if (callchain) {
    + callchain_size = (1 + callchain->nr) * sizeof(u64);
    +
    + header.type |= __PERF_EVENT_CALLCHAIN;
    + header.size += callchain_size;
    + }
    + }
    +
    ret = perf_output_begin(&handle, counter, header.size, nmi);
    if (ret)
    return;
    @@ -1791,6 +1815,9 @@ static void perf_output_simple(struct perf_counter *counter,
    if (counter->hw_event.include_tid)
    perf_output_put(&handle, tid_entry);

    + if (callchain)
    + perf_output_copy(&handle, callchain, callchain_size);
    +
    perf_output_end(&handle);
    }


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