perf intel-pt: Add intel_pt_fast_forward()

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>

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 dde6a7a97a7a3f7d9e6a3abd7e5d3ed996be3d19..c374a856e73fcaf2dc0bf2a5ad4c07129f652927 100644 (file)
--- 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 de36254c6ac993efed8b9cb1bdbe4b791530393a..e633fad2fd5d5ceaf1023b10c5d8e12af1964908 100644 (file)
--- 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);