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    Subject[PATCH 10/19] perf intel-pt: Add support for lookahead
    Date
    Implement the lookahead callback to let the decoder access subsequent
    buffers. intel_pt_lookahead() manages the buffer lifetime and calls the
    decoder for each buffer until the decoder returns a non-zero value.

    Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
    ---
    tools/perf/util/intel-pt.c | 59 +++++++++++++++++++++++++++++++++++++-
    1 file changed, 58 insertions(+), 1 deletion(-)

    diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
    index 4a61c73c9711..3e3a01318b76 100644
    --- a/tools/perf/util/intel-pt.c
    +++ b/tools/perf/util/intel-pt.c
    @@ -278,7 +278,63 @@ static int intel_pt_get_buffer(struct intel_pt_queue *ptq,
    return 0;
    }

    -/* This function assumes data is processed sequentially only */
    +/* Do not drop buffers with references - refer intel_pt_get_trace() */
    +static void intel_pt_lookahead_drop_buffer(struct intel_pt_queue *ptq,
    + struct auxtrace_buffer *buffer)
    +{
    + if (!buffer || buffer == ptq->buffer || buffer == ptq->old_buffer)
    + return;
    +
    + auxtrace_buffer__drop_data(buffer);
    +}
    +
    +/* Must be serialized with respect to intel_pt_get_trace() */
    +static int intel_pt_lookahead(void *data, intel_pt_lookahead_cb_t cb,
    + void *cb_data)
    +{
    + struct intel_pt_queue *ptq = data;
    + struct auxtrace_buffer *buffer = ptq->buffer;
    + struct auxtrace_buffer *old_buffer = ptq->old_buffer;
    + struct auxtrace_queue *queue;
    + int err = 0;
    +
    + queue = &ptq->pt->queues.queue_array[ptq->queue_nr];
    +
    + while (1) {
    + struct intel_pt_buffer b = { .len = 0 };
    +
    + buffer = auxtrace_buffer__next(queue, buffer);
    + if (!buffer)
    + break;
    +
    + err = intel_pt_get_buffer(ptq, buffer, old_buffer, &b);
    + if (err)
    + break;
    +
    + if (b.len) {
    + intel_pt_lookahead_drop_buffer(ptq, old_buffer);
    + old_buffer = buffer;
    + } else {
    + intel_pt_lookahead_drop_buffer(ptq, buffer);
    + continue;
    + }
    +
    + err = cb(&b, cb_data);
    + if (err)
    + break;
    + }
    +
    + if (buffer != old_buffer)
    + intel_pt_lookahead_drop_buffer(ptq, buffer);
    + intel_pt_lookahead_drop_buffer(ptq, old_buffer);
    +
    + return err;
    +}
    +
    +/*
    + * This function assumes data is processed sequentially only.
    + * Must be serialized with respect to intel_pt_lookahead()
    + */
    static int intel_pt_get_trace(struct intel_pt_buffer *b, void *data)
    {
    struct intel_pt_queue *ptq = data;
    @@ -827,6 +883,7 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt,

    params.get_trace = intel_pt_get_trace;
    params.walk_insn = intel_pt_walk_next_insn;
    + params.lookahead = intel_pt_lookahead;
    params.data = ptq;
    params.return_compression = intel_pt_return_compression(pt);
    params.branch_enable = intel_pt_branch_enable(pt);
    --
    2.17.1
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