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Subject[PATCH 70/85] perf intel-pt: Add intel_pt_fast_forward()
Date
From: Adrian Hunter <adrian.hunter@intel.com>

Intel PT decoding is done in time order. In order to support efficient time
interval filtering, add a facility to "fast forward" towards a particular
timestamp. That involves finding the right buffer, stepping to that buffer,
and then stepping forward PSBs. Because decoding must begin at a PSB,
"fast forward" stops at the last PSB that has a timestamp before the target
timestamp.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190604130017.31207-9-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
.../util/intel-pt-decoder/intel-pt-decoder.c | 130 ++++++++++++++++++
.../util/intel-pt-decoder/intel-pt-decoder.h | 2 +
2 files changed, 132 insertions(+)

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index dde6a7a97a7a..c374a856e73f 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -126,6 +126,7 @@ struct intel_pt_decoder {
uint64_t timestamp;
uint64_t tsc_timestamp;
uint64_t ref_timestamp;
+ uint64_t buf_timestamp;
uint64_t sample_timestamp;
uint64_t ret_addr;
uint64_t ctc_timestamp;
@@ -519,6 +520,7 @@ static int intel_pt_get_data(struct intel_pt_decoder *decoder, bool reposition)
intel_pt_log("No more data\n");
return -ENODATA;
}
+ decoder->buf_timestamp = buffer.ref_timestamp;
if (!buffer.consecutive || reposition) {
intel_pt_reposition(decoder);
decoder->ref_timestamp = buffer.ref_timestamp;
@@ -2854,3 +2856,131 @@ unsigned char *intel_pt_find_overlap(unsigned char *buf_a, size_t len_a,
return buf_b; /* No overlap */
}
}
+
+/**
+ * struct fast_forward_data - data used by intel_pt_ff_cb().
+ * @timestamp: timestamp to fast forward towards
+ * @buf_timestamp: buffer timestamp of last buffer with trace data earlier than
+ * the fast forward timestamp.
+ */
+struct fast_forward_data {
+ uint64_t timestamp;
+ uint64_t buf_timestamp;
+};
+
+/**
+ * intel_pt_ff_cb - fast forward lookahead callback.
+ * @buffer: Intel PT trace buffer
+ * @data: opaque pointer to fast forward data (struct fast_forward_data)
+ *
+ * Determine if @buffer trace is past the fast forward timestamp.
+ *
+ * Return: 1 (stop lookahead) if @buffer trace is past the fast forward
+ * timestamp, and 0 otherwise.
+ */
+static int intel_pt_ff_cb(struct intel_pt_buffer *buffer, void *data)
+{
+ struct fast_forward_data *d = data;
+ unsigned char *buf;
+ uint64_t tsc;
+ size_t rem;
+ size_t len;
+
+ buf = (unsigned char *)buffer->buf;
+ len = buffer->len;
+
+ if (!intel_pt_next_psb(&buf, &len) ||
+ !intel_pt_next_tsc(buf, len, &tsc, &rem))
+ return 0;
+
+ tsc = intel_pt_8b_tsc(tsc, buffer->ref_timestamp);
+
+ intel_pt_log("Buffer 1st timestamp " x64_fmt " ref timestamp " x64_fmt "\n",
+ tsc, buffer->ref_timestamp);
+
+ /*
+ * If the buffer contains a timestamp earlier that the fast forward
+ * timestamp, then record it, else stop.
+ */
+ if (tsc < d->timestamp)
+ d->buf_timestamp = buffer->ref_timestamp;
+ else
+ return 1;
+
+ return 0;
+}
+
+/**
+ * intel_pt_fast_forward - reposition decoder forwards.
+ * @decoder: Intel PT decoder
+ * @timestamp: timestamp to fast forward towards
+ *
+ * Reposition decoder at the last PSB with a timestamp earlier than @timestamp.
+ *
+ * Return: 0 on success or negative error code on failure.
+ */
+int intel_pt_fast_forward(struct intel_pt_decoder *decoder, uint64_t timestamp)
+{
+ struct fast_forward_data d = { .timestamp = timestamp };
+ unsigned char *buf;
+ size_t len;
+ int err;
+
+ intel_pt_log("Fast forward towards timestamp " x64_fmt "\n", timestamp);
+
+ /* Find buffer timestamp of buffer to fast forward to */
+ err = decoder->lookahead(decoder->data, intel_pt_ff_cb, &d);
+ if (err < 0)
+ return err;
+
+ /* Walk to buffer with same buffer timestamp */
+ if (d.buf_timestamp) {
+ do {
+ decoder->pos += decoder->len;
+ decoder->len = 0;
+ err = intel_pt_get_next_data(decoder, true);
+ /* -ENOLINK means non-consecutive trace */
+ if (err && err != -ENOLINK)
+ return err;
+ } while (decoder->buf_timestamp != d.buf_timestamp);
+ }
+
+ if (!decoder->buf)
+ return 0;
+
+ buf = (unsigned char *)decoder->buf;
+ len = decoder->len;
+
+ if (!intel_pt_next_psb(&buf, &len))
+ return 0;
+
+ /*
+ * Walk PSBs while the PSB timestamp is less than the fast forward
+ * timestamp.
+ */
+ do {
+ uint64_t tsc;
+ size_t rem;
+
+ if (!intel_pt_next_tsc(buf, len, &tsc, &rem))
+ break;
+ tsc = intel_pt_8b_tsc(tsc, decoder->buf_timestamp);
+ /*
+ * A TSC packet can slip past MTC packets but, after fast
+ * forward, decoding starts at the TSC timestamp. That means
+ * the timestamps may not be exactly the same as the timestamps
+ * that would have been decoded without fast forward.
+ */
+ if (tsc < timestamp) {
+ intel_pt_log("Fast forward to next PSB timestamp " x64_fmt "\n", tsc);
+ decoder->pos += decoder->len - len;
+ decoder->buf = buf;
+ decoder->len = len;
+ intel_pt_reposition(decoder);
+ } else {
+ break;
+ }
+ } while (intel_pt_step_psb(&buf, &len));
+
+ return 0;
+}
diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
index de36254c6ac9..e633fad2fd5d 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
@@ -130,6 +130,8 @@ void intel_pt_decoder_free(struct intel_pt_decoder *decoder);

const struct intel_pt_state *intel_pt_decode(struct intel_pt_decoder *decoder);

+int intel_pt_fast_forward(struct intel_pt_decoder *decoder, uint64_t timestamp);
+
unsigned char *intel_pt_find_overlap(unsigned char *buf_a, size_t len_a,
unsigned char *buf_b, size_t len_b,
bool have_tsc, bool *consecutive);
--
2.20.1
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