[RFC,2/3] kernel-shark-qt: Introduce the visualization model used by the Qt-based KS
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Message ID 20180705153744.28356-2-y.karadz@gmail.com
State New, archived
Headers show
Series
  • [RFC,1/3] kernel-shark-qt: Add generic instruments for searching inside the trace data
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Commit Message

Yordan Karadzhov (VMware) July 5, 2018, 3:37 p.m. UTC
The model, used by the Qt-based KernelShark for visualization of trace data
is build over the concept of "Data Bins". When visualizing a large data-set
of trace records, we are limited by the number of screen pixels available for
drawing. The model divides the data-set into data-units, also called Bins.
The Bin has to be defined in such a way that the entire content of one Bin
can be summarized and visualized by a single graphical element.
This model uses the timestamp of the trace records, as a criteria for forming
Bins. When the Model has to visualize all records inside a given time-window,
it divides this time-window into N smaller, uniformly sized subintervals and
then defines that one Bin contains all trace records, having timestamps
falling into one of this subintervals. Because the model operates over an
array of trace records, sorted in time, the content of each Bin can be
retrieved by simply knowing the index of the first element inside this Bin
and the index of the first element of the next Bin. This means that knowing
the index of the first element in each Bin is enough to determine the State
of the model.

The State of the model can be modified by its five basic operations: Zoon-In,
Zoom-Out, Shift-Forward, Shift-Backward and Jump-To. After each of these
operations, the new State of the model is retrieved, by using binary search
to find the index of the first element in each Bin. This means that each one
of the five basic operations of the model has log(n) time complexity (see
previous change log).

In order to keep the visualization of the new state of the model as efficient
as possible, the model needs a way to summarize and visualize the content of
the Bins in constant time. This is achieved by limiting ourself to only
checking the content of the records at the beginning and at the end of the
Bin. As explaned in the previous change log, this approach has the very
counter-intuitive effect of making the update of the sparse (or empty) Graphs
much slower. The problem of the Sparse Graphs will be addressed in another
patch, where "Data Collections" will be introduced.

The following patch will introduces a simple example, demonstrating the usage
of the API of the Model.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 kernel-shark-qt/src/CMakeLists.txt    |    3 +-
 kernel-shark-qt/src/libkshark-model.c | 1131 +++++++++++++++++++++++++
 kernel-shark-qt/src/libkshark-model.h |  138 +++
 3 files changed, 1271 insertions(+), 1 deletion(-)
 create mode 100644 kernel-shark-qt/src/libkshark-model.c
 create mode 100644 kernel-shark-qt/src/libkshark-model.h

Patch
diff mbox series

diff --git a/kernel-shark-qt/src/CMakeLists.txt b/kernel-shark-qt/src/CMakeLists.txt
index ed3c60e..ec22f63 100644
--- a/kernel-shark-qt/src/CMakeLists.txt
+++ b/kernel-shark-qt/src/CMakeLists.txt
@@ -1,7 +1,8 @@ 
 message("\n src ...")
 
 message(STATUS "libkshark")
-add_library(kshark SHARED libkshark.c)
+add_library(kshark SHARED libkshark.c
+                          libkshark-model.c)
 
 target_link_libraries(kshark ${CMAKE_DL_LIBS}
                              ${TRACEEVENT_LIBRARY}
diff --git a/kernel-shark-qt/src/libkshark-model.c b/kernel-shark-qt/src/libkshark-model.c
new file mode 100644
index 0000000..5f3583f
--- /dev/null
+++ b/kernel-shark-qt/src/libkshark-model.c
@@ -0,0 +1,1131 @@ 
+// SPDX-License-Identifier: LGPL-2.1
+
+/*
+ * Copyright (C) 2017 VMware Inc, Yordan Karadzhov <y.karadz@gmail.com>
+ */
+
+ /**
+ *  @file    libkshark.c
+ *  @brief   Visualization model for FTRACE (trace-cmd) data.
+ */
+
+// C
+#include <stdlib.h>
+
+// KernelShark
+#include "libkshark-model.h"
+
+/**
+ * @brief Initialize the Visualization model.
+ * @param histo: Input location for the model descriptor.
+ */
+void ksmodel_init(struct kshark_trace_histo *histo)
+{
+	/*
+	 * Initialize an empty histo. The histo will have no bins and will
+	 * contain no data.
+	 */
+	histo->bin_size = 0;
+	histo->min = 0;
+	histo->max = 0;
+	histo->n_bins = 0;
+
+	histo->bin_count = NULL;
+	histo->map = NULL;
+}
+
+/**
+ * @brief Clear (reset) the Visualization model.
+ * @param histo: Input location for the model descriptor.
+ */
+void ksmodel_clear(struct kshark_trace_histo *histo)
+{
+	/* Reset the histo. It will have no bins and will contain no data. */
+	histo->bin_size = 0;
+	histo->min = 0;
+	histo->max = 0;
+	histo->n_bins = 0;
+
+	free(histo->map);
+	histo->map = NULL;
+
+	free(histo->bin_count);
+	histo->bin_count = NULL;
+}
+
+static void ksmodel_reset_bins(struct kshark_trace_histo *histo,
+			       size_t first, size_t last)
+{
+	size_t i;
+
+	/* Reset the content of the bins. */
+	for (i = first; i <= last; ++i) {
+		histo->map[i] = KS_EMPTY_BIN;
+		histo->bin_count[i] = 0;
+	}
+}
+
+static void ksmodel_histo_alloc(struct kshark_trace_histo *histo, size_t n)
+{
+	free(histo->bin_count);
+	free(histo->map);
+
+	/* Create bins. Two overflow bins are added. */
+	histo->map = calloc(n + 2, sizeof(*histo->map));
+	histo->bin_count = calloc(n + 2, sizeof(*histo->bin_count));
+
+	if (!histo->map || !histo->bin_count) {
+		ksmodel_clear(histo);
+		fprintf(stderr, "Failed to allocate memory for a histo.\n");
+		return;
+	}
+
+	histo->n_bins = n;
+}
+
+static void ksmodel_set_in_range_bining(struct kshark_trace_histo *histo,
+					size_t n, uint64_t min, uint64_t max,
+					bool force_in_range)
+{
+	uint64_t corrected_range, delta_range, range = max - min;
+	struct kshark_entry *last;
+
+	/* The size of the bin must be >= 1, hence the range must be >= n. */
+	if (n == 0 || range < n)
+		return;
+
+	/*
+	 * If the number of bins changes, allocate memory for the descriptor
+	 * of the model.
+	 */
+	if (n != histo->n_bins) {
+		ksmodel_histo_alloc(histo, n);
+	}
+
+	/* Reset the content of all bins (including overflow bins) to zero. */
+	ksmodel_reset_bins(histo, 0, histo->n_bins + 1);
+
+	if (range % n == 0) {
+		/*
+		 * The range is multiple of the number of bin and needs no
+		 * adjustment. This is very unlikely to happen but still ...
+		 */
+		histo->min = min;
+		histo->max = max;
+		histo->bin_size = range / n;
+	} else {
+		/*
+		 * The range needs adjustment. The new range will be slightly
+		 * bigger, compared to the requested one.
+		 */
+		histo->bin_size = range / n + 1;
+		corrected_range = histo->bin_size * n;
+		delta_range = corrected_range - range;
+		histo->min = min - delta_range / 2;
+		histo->max = histo->min + corrected_range;
+
+		if (!force_in_range)
+			return;
+
+		/*
+		 * Make sure that the new range doesn't go outside of the time
+		 * interval of the dataset.
+		 */
+		last = histo->data[histo->data_size - 1];
+		if (histo->min < histo->data[0]->ts) {
+			histo->min = histo->data[0]->ts;
+			histo->max = histo->min + corrected_range;
+		} else if (histo->max > last->ts) {
+			histo->max = last->ts;
+			histo->min = histo->max - corrected_range;
+		}
+	}
+}
+
+/**
+ * @brief Prepare the bining of the Visualization model.
+ * @param histo: Input location for the model descriptor.
+ * @param n: Number of bins.
+ * @param min: Lower edge of the time-window to be visualized.
+ * @param max: Upper edge of the time-window to be visualized.
+ */
+void ksmodel_set_bining(struct kshark_trace_histo *histo,
+			size_t n, uint64_t min, uint64_t max)
+{
+	ksmodel_set_in_range_bining(histo, n, min, max, false);
+}
+
+static size_t ksmodel_set_lower_edge(struct kshark_trace_histo *histo)
+{
+	/*
+	 * Find the index of the first entry inside
+	 * the range (timestamp > min).
+	 */
+	size_t row = kshark_find_entry_by_time(histo->min,
+					       histo->data,
+					       0,
+					       histo->data_size - 1);
+
+	if (row != 0) {
+		/*
+		 * The first entry inside the range is not the first entry
+		 * of the dataset. This means that the Lower Overflow bin
+		 * contains data.
+		 */
+
+		/* Lower Overflow bin starts at "0". */
+		histo->map[histo->n_bins + 1] = 0;
+
+		/*
+		 * The number of entries inside the Lower Overflow bin is
+		 * equal to the index of the first entry inside the range.
+		 */
+		histo->bin_count[histo->n_bins + 1] = row;
+	}  else {
+		/*
+		 * Lower Overflow bin is empty. The number of entries is
+		 * already set to "0".
+		 */
+		histo->map[histo->n_bins + 1] = KS_EMPTY_BIN;
+	}
+
+	/*
+	 * Now check if the first entry inside the range falls into the
+	 * first bin.
+	 */
+	if (histo->data[row]->ts  < histo->min + histo->bin_size) {
+		/*
+		 * It is inside the fisrs bin. Set the beginning
+		 * of the fisrs bin.
+		 */
+		histo->map[0] = row;
+	} else {
+		/* The fisrs bin is empty. */
+		histo->map[0] = KS_EMPTY_BIN;
+	}
+
+	return row;
+}
+
+static size_t ksmodel_set_upper_edge(struct kshark_trace_histo *histo)
+{
+	/*
+	 * Find the index of the first entry outside
+	 * the range (timestamp > max).
+	 */
+	size_t row = kshark_find_entry_by_time(histo->max,
+					       histo->data,
+					       0,
+					       histo->data_size - 1);
+
+	if (row < histo->data_size - 1 ||
+	    (row == histo->data_size - 1 &&
+	     histo->data[histo->data_size - 1]->ts > histo->max)) {
+		/*
+		 * The Upper Overflow bin contains data. Set its beginning
+		 * and the number of entries.
+		 */
+		histo->map[histo->n_bins] = row;
+		histo->bin_count[histo->n_bins] = histo->data_size - row;
+	}  else {
+		/*
+		 * Upper Overflow bin is empty. The number of entries is
+		 * already set to "0".
+		 */
+		histo->map[histo->n_bins] = KS_EMPTY_BIN;
+	}
+
+	return row;
+}
+
+static void ksmodel_set_next_bin_edge(struct kshark_trace_histo *histo,
+				      size_t bin)
+{
+	size_t time, row, next_bin = bin + 1;
+
+	/* Calculate the beginning of the next bin. */
+	time = histo->min + next_bin * histo->bin_size;
+
+	/*
+	 * Find the index of the first entry inside
+	 * the next bin (timestamp > time).
+	 */
+	row = kshark_find_entry_by_time(time,histo->data, 0,
+					histo->data_size - 1);
+
+	/*
+	 * The timestamp of the very last entry of the dataset can be exactly
+	 * equal to the value of the upper edge of the range. This is very
+	 * likely to happen when we use ksmodel_set_in_range_bining(). In this
+	 * case we have to increase the size of the very last bin in order to
+	 * make sure that the last entry of the dataset will fall into it.
+	 */
+	if (next_bin == histo->n_bins - 1)
+		++time;
+
+	if (histo->data[row]->ts  >= time + histo->bin_size) {
+		/* The bin is empty. */
+		histo->map[next_bin] = KS_EMPTY_BIN;
+		return;
+	}
+
+	/* Set the index of the first entry. */
+	histo->map[next_bin] = row;
+}
+
+static void ksmodel_set_bin_counts(struct kshark_trace_histo *histo)
+{
+	size_t i = 0, prev_not_empty;
+
+	/*
+	 * Find the first bin which contain data. Start by checking the
+	 * Lower Overflow bin.
+	 */
+	if (histo->map[histo->n_bins + 1] != KS_EMPTY_BIN) {
+		prev_not_empty = histo->n_bins + 1;
+	} else {
+		while (histo->map[i] < 0) {
+			++i;
+		}
+
+		prev_not_empty = i++;
+	}
+
+	/*
+	 * Starting from the first not empty bin, loop over all bins and
+	 * calculate the number of entries.
+	 */
+	while (i < histo->n_bins) {
+		if (histo->map[i] != KS_EMPTY_BIN) {
+			histo->bin_count[prev_not_empty] =
+				histo->map[i] - histo->map[prev_not_empty];
+	
+			prev_not_empty = i;
+		}
+
+		++i;
+	}
+
+	/* Check if the Upper Overflow bin contains data. */
+	if (histo->map[histo->n_bins] == KS_EMPTY_BIN) {
+		/*
+		 * The Upper Overflow bin is empty. Use the size of the
+		 * dataset to calculate the content of the previouse not
+		 * empty bin.
+		 */
+		histo->bin_count[prev_not_empty] = histo->data_size -
+						   histo->map[prev_not_empty];
+	} else {
+		/*
+		 * Use the index of the first entry inside the Upper Overflow
+		 * bin to calculate the content of the previouse not empty
+		 * bin.
+		 */
+		histo->bin_count[prev_not_empty] = histo->map[histo->n_bins] -
+						   histo->map[prev_not_empty];
+	}
+}
+
+/**
+ * @brief Provide the Visualization model with data. Calculate the current
+ *	  state of the model.
+ * @param histo: Input location for the model descriptor.
+ * @param data: Input location for the trace data.
+ * @param n: Number of bins.
+ */
+void ksmodel_fill(struct kshark_trace_histo *histo,
+		  struct kshark_entry **data, size_t n)
+{
+	size_t bin;
+
+	histo->data_size = n;
+	histo->data = data;
+
+	if (histo->n_bins == 0 ||
+	    histo->bin_size == 0 ||
+	    histo->data_size == 0) {
+		/*
+		 * Something is wrong with this histo.
+		 * Most likely the binning is not set.
+		 */
+		ksmodel_clear(histo);
+		fprintf(stderr,
+			"Unable to fill the model with data.\n");
+		fprintf(stderr,
+			"Try to set the bining of the model first.\n");
+
+		return;
+	}
+
+	/* Set the Lower Overflow bin */
+	ksmodel_set_lower_edge(histo);
+
+	/*
+	 * Loop over the dataset and set the beginning of all individual bins.
+	 */
+	bin = 0;
+	while (bin < histo->n_bins) {
+		ksmodel_set_next_bin_edge(histo, bin);
+		++bin;
+	}
+
+	/* Set the Upper Overflow bin. */
+	ksmodel_set_upper_edge(histo);
+
+	/* Calculate the number of entries in each bin. */
+	ksmodel_set_bin_counts(histo);
+}
+
+/**
+ * @brief Get the total number of entries in a given bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @returns The number of entries in this bin.
+ */
+size_t ksmodel_bin_count(struct kshark_trace_histo *histo, int bin)
+{
+	if (bin >= 0 && bin < (int) histo->n_bins)
+		return histo->bin_count[bin];
+
+	if (bin == UPPER_OVERFLOW_BIN)
+		return histo->bin_count[histo->n_bins];
+
+	if (bin == LOWER_OVERFLOW_BIN)
+		return histo->bin_count[histo->n_bins + 1];
+
+	return 0;
+}
+
+/**
+ * @brief Shift the time-window of the model forward. Recalculate the current
+ *	  state of the model.
+ * @param histo: Input location for the model descriptor.
+ * @param n: Number of bins to shift.
+ */
+void ksmodel_shift_forward(struct kshark_trace_histo *histo, size_t n)
+{
+	size_t bin;
+	
+	if (!histo->data_size)
+		return;
+
+	if (ksmodel_bin_count(histo, UPPER_OVERFLOW_BIN) == 0) {
+		/*
+		 * The Upper Overflow bin is empty. This means that we are at
+		 * the upper edge of the dataset already. Do nothing in this
+		 * case.
+		 */
+		return;
+	}
+
+	if (n >= histo->n_bins) {
+		/*
+		 * No overlap between the new and the old ranges. Recalculate
+		 * all bins from scratch. First calculate the new range.
+		 */
+		histo->min += n * histo->bin_size;
+		histo->max += n * histo->bin_size;
+
+		ksmodel_set_bining(histo, histo->n_bins, histo->min,
+							 histo->max);
+
+		ksmodel_fill(histo, histo->data, histo->data_size);
+		return;
+	}
+
+	/* Set the new Lower Overflow bin */
+	ksmodel_set_lower_edge(histo);
+
+	/*
+	 * Copy the content of all overlaping bins starting from bin "0"
+	 * of the new histo.
+	 */
+	bin = 0;
+	while (bin <  histo->n_bins - n) {
+		histo->map[bin] = histo->map[bin + n];
+		histo->bin_count[bin] = histo->bin_count[bin + n];
+		++bin;
+	}
+
+	histo->map[bin] = histo->map[bin + n];
+	histo->bin_count[bin] = 0;
+
+	/* Calculate only the content of the new (non-overlapping) bins. */
+	ksmodel_reset_bins(histo, bin + 1, histo->n_bins);
+	while (bin < histo->n_bins) {
+		ksmodel_set_next_bin_edge(histo, bin);
+		++bin;
+	}
+
+	/*
+	 * Set the new Upper Overflow bin and calculate the number of entries
+	 * in each bin.
+	 */
+	ksmodel_set_upper_edge(histo);
+	ksmodel_set_bin_counts(histo);
+}
+
+/**
+ * @brief Shift the time-window of the model backward. Recalculate the current
+ *	  state of the model.
+ * @param histo: Input location for the model descriptor.
+ * @param n: Number of bins to shift.
+ */
+void ksmodel_shift_backward(struct kshark_trace_histo *histo, size_t n)
+{
+	size_t bin;
+
+	if (!histo->data_size)
+		return;
+
+	if (ksmodel_bin_count(histo, LOWER_OVERFLOW_BIN) == 0) {
+		/*
+		 * The Lower Overflow bin is empty. This means that we are at
+		 * the Lower edge of the dataset already. Do nothing in this
+		 * case.
+		 */
+		return;
+	}
+
+	if (n >= histo->n_bins) {
+		/*
+		 * No overlap between the new and the old range. Recalculate
+		 * all bins from scratch. First calculate the new range.
+		 */
+		histo->min -= n * histo->bin_size;
+		histo->max -= n * histo->bin_size;
+
+		ksmodel_set_bining(histo, histo->n_bins, histo->min,
+							 histo->max);
+
+		ksmodel_fill(histo, histo->data, histo->data_size);
+		return;
+	}
+
+	/*
+	 * Copy the content of all overlaping bins starting from the last bin
+	 * of the new histo.
+	 */
+	bin = histo->n_bins - 1;
+	while (1) {
+		if (bin > histo->n_bins - n && histo->map[bin] >= 0) {
+			histo->map[histo->n_bins] = histo->map[bin];
+			histo->bin_count[histo->n_bins] +=
+				histo->bin_count[bin];
+		}
+
+		histo->map[bin] = histo->map[bin-n];
+		histo->bin_count[bin] = histo->bin_count[bin-n];
+
+		if (bin == n)
+			break;
+
+		--bin;
+	}
+
+	/* Reset all new bins, including overflow bins. */
+	ksmodel_reset_bins(histo, 0, bin);
+	ksmodel_reset_bins(histo, histo->n_bins, histo->n_bins + 1);
+
+	/* Set the new Lower Overflow bin */
+	ksmodel_set_lower_edge(histo);
+
+	/* Calculate only the content of the new (non-overlapping) bins. */
+	bin = 0;
+	while (bin < n) {
+		ksmodel_set_next_bin_edge(histo, bin);
+		++bin;
+	}
+
+	/*
+	 * Set the new Upper Overflow bin and calculate the number of entries
+	 * in each bin.
+	 */
+	ksmodel_set_upper_edge(histo);
+	ksmodel_set_bin_counts(histo);
+}
+
+/**
+ * @brief Move the time-window of the model to a given location. Recalculate
+ *	  the current state of the model.
+ * @param histo: Input location for the model descriptor.
+ * @param ts: position in time to be visualized.
+ */
+void ksmodel_jump_to(struct kshark_trace_histo *histo, size_t ts)
+{
+	size_t min, max, range_min;
+
+	if (ts > histo->min && ts < histo->max) {
+		/*
+		 * The new position is already inside the range.
+		 * Do nothing in this case.
+		 */
+		return;
+	}
+
+	/*
+	 * Calculate the new range without changing the size and the number
+	 * of bins.
+	 */
+	min = ts - histo->n_bins * histo->bin_size / 2;
+
+	/* Make sure that the range does not go outside of the dataset. */
+	if (min < histo->data[0]->ts)
+		min = histo->data[0]->ts;
+
+	range_min = histo->data[histo->data_size - 1]->ts -
+		   histo->n_bins * histo->bin_size;
+
+	if (min > range_min)
+		min = range_min;
+
+	max = min + histo->n_bins * histo->bin_size;
+
+	/* Use the new range to recalculate all bins from scratch. */
+	ksmodel_set_bining(histo, histo->n_bins, min, max);
+	ksmodel_fill(histo, histo->data, histo->data_size);
+}
+
+/**
+ * @brief Extend the time-window of the model. Recalculate the current state
+ *	  of the model.
+ * @param histo: Input location for the model descriptor.
+ * @param r: Scale factor of the zoom-out.
+ * @param mark: Focus point of the zoom-out.
+ */
+void ksmodel_zoom_out(struct kshark_trace_histo *histo,
+		      double r, int mark)
+{
+	size_t range, min, max, delta_min;
+	double delta_tot;
+
+	if (!histo->data_size) 
+		return;
+
+	/*
+	 * If the marker is not set, assume that the focal point of the zoom
+	 * is the center of the range.
+	 */
+	if (mark < 0)
+		mark = histo->n_bins / 2;
+
+	/*
+	 * Calculate the new range of the histo. Use the bin of the marker
+	 * as a focal point for the zoomout. With this the maker will stay
+	 * inside the same bin in the new histo.
+	 */
+	range = histo->max - histo->min;
+	delta_tot = range * r;
+	delta_min = delta_tot * mark / histo->n_bins;
+
+	min = histo->min - delta_min;
+	max = histo->max + (size_t) delta_tot - delta_min;
+
+	/* Make sure the new range doesn't go outside of the dataset. */
+	if (min < histo->data[0]->ts)
+		min = histo->data[0]->ts;
+
+	if (max > histo->data[histo->data_size - 1]->ts)
+		max = histo->data[histo->data_size - 1]->ts;
+
+	/*
+	 * Use the new range to recalculate all bins from scratch. Enforce
+	 * "In Range" adjustment of the range of the model, in order to avoid
+	 * slowly drifting outside of the data-set in the case when the very
+	 * first or the very last entry is used as a focal point.
+	 */
+	ksmodel_set_in_range_bining(histo, histo->n_bins, min, max, true);
+	ksmodel_fill(histo, histo->data, histo->data_size);
+}
+
+/**
+ * @brief Shrink the time-window of the model. Recalculate the current state
+ *	  of the model.
+ * @param histo: Input location for the model descriptor.
+ * @param r: Scale factor of the zoom-in.
+ * @param mark: Focus point of the zoom-in.
+ */
+void ksmodel_zoom_in(struct kshark_trace_histo *histo,
+		     double r, int mark)
+{
+	size_t range, min, max, delta_min;
+	double delta_tot;
+
+	if (!histo->data_size)
+		return;
+
+	/*
+	 * If the marker is not set, assume that the focal point of the zoom
+	 * is the center of the range.
+	 */
+	if (mark < 0)
+		mark = histo->n_bins / 2;
+
+	range = histo->max - histo->min;
+
+	/* Avoid overzooming. */
+	if (range < histo->n_bins * 4)
+		return;
+
+	/*
+	 * Calculate the new range of the histo. Use the bin of the marker
+	 * as a focal point for the zoomin. With this the maker will stay
+	 * inside the same bin in the new histo.
+	 */
+	delta_tot =  range * r;
+	if (mark == (int)histo->n_bins - 1)
+		delta_min = delta_tot;
+	else if (mark == 0)
+		delta_min = 0;
+	else
+		delta_min = delta_tot * mark / histo->n_bins;
+
+	min = histo->min + delta_min;
+	max = histo->max - (size_t) delta_tot + delta_min;
+
+	/*
+	 * Use the new range to recalculate all bins from scratch. Enforce
+	 * "In Range" adjustment of the range of the model, in order to avoid
+	 * slowly drifting outside of the data-set in the case when the very
+	 * first or the very last entry is used as a focal point.
+	 */
+	ksmodel_set_in_range_bining(histo, histo->n_bins, min, max, true);
+	ksmodel_fill(histo, histo->data, histo->data_size);
+}
+
+/**
+ * @brief Get the index of the first entry in a given bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @returns Index of the first entry in this bin. If the bin is empty the
+ *	    function returns negative error identifier (KS_EMPTY_BIN).
+ */
+ssize_t ksmodel_first_index_at_bin(struct kshark_trace_histo *histo, int bin)
+{
+	if (bin >= 0 && bin < (int) histo->n_bins)
+		return histo->map[bin];
+
+	if (bin == UPPER_OVERFLOW_BIN)
+		return histo->map[histo->n_bins];
+
+	if (bin == LOWER_OVERFLOW_BIN)
+		return histo->map[histo->n_bins + 1];
+
+	return KS_EMPTY_BIN;
+}
+
+/**
+ * @brief Get the index of the last entry in a given bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @returns Index of the last entry in this bin. If the bin is empty the
+ *	    function returns negative error identifier (KS_EMPTY_BIN).
+ */
+ssize_t ksmodel_last_index_at_bin(struct kshark_trace_histo *histo, int bin)
+{
+	ssize_t index = ksmodel_first_index_at_bin(histo, bin);
+	size_t count = ksmodel_bin_count(histo, bin);
+
+	if (index >= 0 && count)
+		index += count - 1;
+
+	return index;
+}
+
+static bool ksmodel_is_visible(struct kshark_entry *e)
+{
+	if ((e->visible & KS_GRAPH_VIEW_FILTER_MASK) &&
+	    (e->visible & KS_EVENT_VIEW_FILTER_MASK))
+		return true;
+
+	return false;
+}
+
+static struct kshark_entry_request *
+ksmodel_entry_front_request_alloc(struct kshark_trace_histo *histo,
+				  int bin, bool vis_only,
+				  matching_condition_func func, int val)
+{
+	struct kshark_entry_request *req;
+	size_t first, n;
+
+	/* Get the number of entries in this bin. */
+	n = ksmodel_bin_count(histo, bin);
+	if (!n)
+		return NULL;
+
+	first = ksmodel_first_index_at_bin(histo, bin);
+
+	req = kshark_entry_request_alloc(first, n,
+					 func, val,
+					 vis_only, KS_GRAPH_VIEW_FILTER_MASK);
+
+	return req;
+}
+
+static struct kshark_entry_request *
+ksmodel_entry_back_request_alloc(struct kshark_trace_histo *histo,
+				 int bin, bool vis_only,
+				 matching_condition_func func, int val)
+{
+	struct kshark_entry_request *req;
+	size_t first, n;
+
+	/* Get the number of entries in this bin. */
+	n = ksmodel_bin_count(histo, bin);
+	if (!n)
+		return NULL;
+
+	first = ksmodel_last_index_at_bin(histo, bin);
+
+	req = kshark_entry_request_alloc(first, n,
+					 func, val,
+					 vis_only, KS_GRAPH_VIEW_FILTER_MASK);
+
+	return req;
+}
+
+/**
+ * @brief Get the index of the first entry from a given Cpu in a given bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param cpu: Cpu Id.
+ * @returns Index of the first entry from a given Cpu in this bin.
+ */
+ssize_t ksmodel_first_index_at_cpu(struct kshark_trace_histo *histo,
+				   int bin, int cpu)
+{
+	size_t i, n, first, not_found = KS_EMPTY_BIN;
+
+	n = ksmodel_bin_count(histo, bin);
+	if (!n)
+		return not_found;
+
+	first = ksmodel_first_index_at_bin(histo, bin);
+
+	for (i = first; i < first + n; ++i) {
+		if (histo->data[i]->cpu == cpu) {
+			if (ksmodel_is_visible(histo->data[i]))
+				return i;
+			else
+				not_found = KS_FILTERED_BIN;
+		}
+	}
+
+	return not_found;
+}
+
+/**
+ * @brief Get the index of the first entry from a given Task in a given bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param pid: Process Id of a task.
+ * @returns Index of the first entry from a given Task in this bin.
+ */
+ssize_t ksmodel_first_index_at_pid(struct kshark_trace_histo *histo,
+				   int bin, int pid)
+{
+	size_t i, n, first, not_found = KS_EMPTY_BIN;
+
+	n = ksmodel_bin_count(histo, bin);
+	if (!n)
+		return not_found;
+
+	first = ksmodel_first_index_at_bin(histo, bin);
+	
+	for (i = first; i < first + n; ++i) {
+		if (histo->data[i]->pid == pid) {
+			if (ksmodel_is_visible(histo->data[i]))
+				return i;
+			else
+				not_found = KS_FILTERED_BIN;
+		}
+	}
+
+	return not_found;
+}
+
+/**
+ * @brief In a given bin, start from the front end of the bin and go towards
+ *	  the back end, searching for an entry satisfying the Matching
+ *	  condition defined by a Matching condition function.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param vis_only: If true, a visible entry is requested.
+ * @param func: Matching condition finction.
+ * @param val: Matching condition value, used by the Matching condition
+ *	       finction.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns Pointer ot a kshark_entry, if an entry has been found. Else NULL.
+ */
+const struct kshark_entry *
+ksmodel_get_entry_front(struct kshark_trace_histo *histo,
+			int bin, bool vis_only,
+			matching_condition_func func, int val,
+			ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+
+	/* Set the position at the beginning of the bin and go forward. */
+	req = ksmodel_entry_front_request_alloc(histo, bin, vis_only,
+							    func, val);
+	if (!req)
+		return NULL;
+
+	entry = kshark_get_entry_front(req, histo->data, index);
+	free(req);
+
+	return entry;
+}
+
+/**
+ * @brief In a given bin, start from the back end of the bin and go towards
+ *	  the front end, searching for an entry satisfying the Matching
+ *	  condition defined by a Matching condition function.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param vis_only: If true, a visible entry is requested.
+ * @param func: Matching condition finction.
+ * @param val: Matching condition value, used by the Matching condition
+ *	       finction.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns Pointer ot a kshark_entry, if an entry has been found. Else NULL.
+ */
+const struct kshark_entry *
+ksmodel_get_entry_back(struct kshark_trace_histo *histo,
+		       int bin, bool vis_only,
+		       matching_condition_func func, int val,
+		       ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+
+	/* Set the position at the end of the bin and go backwards. */
+	req = ksmodel_entry_back_request_alloc(histo, bin, vis_only,
+							   func, val);
+	if (!req)
+		return NULL;
+
+	entry = kshark_get_entry_back(req, histo->data, index);
+	free(req);
+
+	return entry;
+}
+
+static int ksmodel_get_entry_pid(const struct kshark_entry *entry)
+{
+	if (!entry) {
+		/* No data has been found. */
+		return KS_EMPTY_BIN;
+	}
+
+	if (!entry->visible) {
+		/* Some data has been found, but it is filtered-out. */
+		return KS_FILTERED_BIN;
+	}
+
+	return entry->pid;
+}
+
+/**
+ * @brief In a given bin, start from the front end of the bin and go towards
+ *	  the back end, searching for an entry from a given Cpu. Return
+ *	  the Process Id of the task of the entry found.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param cpu: Cpu Id.
+ * @param vis_only: If true, a visible entry is requested.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns Process Id of the task if an entry has been found. Else a negative
+ *	    Identifier (KS_EMPTY_BIN or KS_FILTERED_BIN).
+ */
+int ksmodel_get_pid_front(struct kshark_trace_histo *histo,
+			  int bin, int cpu, bool vis_only,
+			  ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+
+	/* Set the position at the beginning of the bin and go forward. */
+	req = ksmodel_entry_front_request_alloc(histo,
+						bin, vis_only,
+						kshark_check_cpu, cpu);
+	if (!req)
+		return KS_EMPTY_BIN;
+
+	entry = kshark_get_entry_front(req, histo->data, index);
+	free(req);
+
+	return ksmodel_get_entry_pid(entry);
+}
+
+/**
+ * @brief In a given bin, start from the back end of the bin and go towards
+ *	  the front end, searching for an entry from a given Cpu. Return
+ *	  the Process Id of the task of the entry found.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param cpu: Cpu Id.
+ * @param vis_only: If true, a visible entry is requested.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns Process Id of the task if an entry has been found. Else a negative
+ *	    Identifier (KS_EMPTY_BIN or KS_FILTERED_BIN).
+ */
+int ksmodel_get_pid_back(struct kshark_trace_histo *histo,
+			 int bin, int cpu, bool vis_only,
+			 ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+
+	/* Set the position at the end of the bin and go backwards. */
+	req = ksmodel_entry_back_request_alloc(histo,
+					       bin, vis_only,
+					       kshark_check_cpu, cpu);
+	if (!req)
+		return KS_EMPTY_BIN;
+
+	entry = kshark_get_entry_back(req, histo->data, index);
+	free(req);
+
+	return ksmodel_get_entry_pid(entry);
+}
+
+static int ksmodel_get_entry_cpu(const struct kshark_entry *entry)
+{
+	if (!entry) {
+		/* No data has been found. */
+		return KS_EMPTY_BIN;
+	}
+
+	if (!entry->visible) {
+		/* Some data has been found, but it is filtered-out. */
+		return KS_FILTERED_BIN;
+	}
+
+	return entry->cpu;
+}
+
+/**
+ * @brief Get the Cpu Id of the first entry from a given Task in a given bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param pid: Process Id of a task.
+ * @param vis_only: If true, a visible entry is requested.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns Cpu Id of the first entry from a given Task in this bin.
+ */
+int ksmodel_get_cpu(struct kshark_trace_histo *histo,
+		    int bin, int pid, bool vis_only,
+		    ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+	size_t n;
+
+	/* Get the number of entries in this bin. */
+	n = ksmodel_bin_count(histo, bin);
+	if (!n)
+		return KS_EMPTY_BIN;
+
+	/* Create an entry request but keep the starting position unset. */
+	req = kshark_entry_request_alloc(0, n,
+					 kshark_check_pid, pid,
+					 vis_only, KS_GRAPH_VIEW_FILTER_MASK);
+
+	if (bin == UPPER_OVERFLOW_BIN) {
+		/*
+		 * Set the position at the end of the Lower Overflow bin and
+		 * go backwards.
+		 */
+		req->first = ksmodel_bin_count(histo, bin) - 1;
+		entry = kshark_get_entry_back(req, histo->data, index);
+	} else {
+		/*
+		 * Set the position at the beginning of the bin and go
+		 * forward.
+		 */
+		req->first = ksmodel_first_index_at_bin(histo, bin);
+		entry = kshark_get_entry_front(req, histo->data, index);
+	}
+
+	free(req);
+
+	return ksmodel_get_entry_cpu(entry);
+}
+
+/**
+ * @brief Check if a visible entry from a given Cpu exist in this bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param cpu: Cpu Id.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns True, if a visible entry from the Cpu exists in this bin.
+ * 	    Else false.
+ */
+bool ksmodel_cpu_visible_event_exist(struct kshark_trace_histo *histo,
+				     int bin, int cpu, ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+
+	/* Set the position at the beginning of the bin and go forward. */
+	req = ksmodel_entry_front_request_alloc(histo,
+						bin, true,
+						kshark_check_cpu, cpu);
+	if (!req)
+		return false;
+
+	req->vis_mask = KS_EVENT_VIEW_FILTER_MASK;
+	entry = kshark_get_entry_front(req, histo->data, index);
+	free(req);
+
+	if (!entry || !entry->visible) {
+		/* No visible entry has been found. */
+		return false;
+	}
+
+	return true;
+}
+
+/**
+ * @brief Check if a visible entry from a given Task exist in this bin.
+ * @param histo: Input location for the model descriptor.
+ * @param bin: Bin id.
+ * @param pid: Process Id of the task.
+ * @param index: Optional output location for the index of the requested
+ *		 entry inside the array.
+ * @returns True, if a visible entry from the task exists in this bin.
+ * 	    Else false.
+ */
+bool ksmodel_task_visible_event_exist(struct kshark_trace_histo *histo,
+				      int bin, int pid, ssize_t *index)
+{
+	struct kshark_entry_request *req;
+	const struct kshark_entry *entry;
+
+	/* Set the position at the beginning of the bin and go forward. */
+	req = ksmodel_entry_front_request_alloc(histo,
+						bin, true,
+						kshark_check_pid, pid);
+	if (!req)
+		return false;
+
+	req->vis_mask = KS_EVENT_VIEW_FILTER_MASK;
+	entry = kshark_get_entry_front(req, histo->data, index);
+	free(req);
+
+	if (!entry || !entry->visible) {
+		/* No visible entry has been found. */
+		return false;
+	}
+
+	return true;
+}
diff --git a/kernel-shark-qt/src/libkshark-model.h b/kernel-shark-qt/src/libkshark-model.h
new file mode 100644
index 0000000..9b2c54c
--- /dev/null
+++ b/kernel-shark-qt/src/libkshark-model.h
@@ -0,0 +1,138 @@ 
+/* SPDX-License-Identifier: LGPL-2.1 */
+
+/*
+ * Copyright (C) 2017 VMware Inc, Yordan Karadzhov <y.karadz@gmail.com>
+ */
+
+ /**
+ *  @file    libkshark-model.h
+ *  @brief   Visualization model for FTRACE (trace-cmd) data.
+ */
+
+#ifndef _LIB_KSHARK_MODEL_H
+#define _LIB_KSHARK_MODEL_H
+
+// KernelShark
+#include "libkshark.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+/** Overflow Bin identifiers. */
+enum OverflowBin {
+	/** Identifier of the Upper Overflow Bin. */
+	UPPER_OVERFLOW_BIN = -1,
+
+	/** Identifier of the Lower Overflow Bin. */
+	LOWER_OVERFLOW_BIN = -2,
+};
+
+/** Structure describing the current state of the visualization model. */
+struct kshark_trace_histo {
+	/** Trace data. */
+	struct kshark_entry	**data;
+
+	/** The size of the data. */
+	size_t			data_size;
+
+	/** The index of the first entry in each bin. */
+	ssize_t			*map;
+
+	/** Number of entries in each bin. */
+	size_t			*bin_count;
+
+	/** Lower edge of the time-window to be visualized. */
+	uint64_t		min;
+
+	/** Upper edge of the time-window to be visualized. */
+	uint64_t		max;
+
+	/** The size of the bins. */
+	uint64_t		bin_size;
+
+	/** Number of bins. */
+	size_t			n_bins;
+};
+
+void ksmodel_init(struct kshark_trace_histo *histo);
+
+void ksmodel_clear(struct kshark_trace_histo *histo);
+
+void ksmodel_set_bining(struct kshark_trace_histo *histo,
+			size_t n, uint64_t min, uint64_t max);
+
+void ksmodel_fill(struct kshark_trace_histo *histo,
+		  struct kshark_entry **data, size_t n);
+
+size_t ksmodel_bin_count(struct kshark_trace_histo *histo, int bin);
+
+void ksmodel_shift_forward(struct kshark_trace_histo *histo, size_t n);
+
+void ksmodel_shift_backward(struct kshark_trace_histo *histo, size_t n);
+
+void ksmodel_jump_to(struct kshark_trace_histo *histo, size_t ts);
+
+void ksmodel_zoom_out(struct kshark_trace_histo *histo,
+		      double r, int mark);
+
+void ksmodel_zoom_in(struct kshark_trace_histo *histo,
+		     double r, int mark);
+
+ssize_t ksmodel_first_index_at_bin(struct kshark_trace_histo *histo, int bin);
+
+ssize_t ksmodel_last_index_at_bin(struct kshark_trace_histo *histo, int bin);
+
+ssize_t ksmodel_first_index_at_cpu(struct kshark_trace_histo *histo,
+				   int bin, int cpu);
+
+ssize_t ksmodel_first_index_at_pid(struct kshark_trace_histo *histo,
+				   int bin, int pid);
+
+const struct kshark_entry *
+ksmodel_get_entry_front(struct kshark_trace_histo *histo,
+			int bin, bool vis_only,
+			matching_condition_func func, int val,
+			ssize_t *index);
+
+const struct kshark_entry *
+ksmodel_get_entry_back(struct kshark_trace_histo *histo,
+		       int bin, bool vis_only,
+		       matching_condition_func func, int val,
+		       ssize_t *index);
+
+int ksmodel_get_pid_front(struct kshark_trace_histo *histo,
+			  int bin, int cpu, bool vis_only,
+			  ssize_t *index);
+
+int ksmodel_get_pid_back(struct kshark_trace_histo *histo,
+			 int bin, int cpu, bool vis_only,
+			 ssize_t *index);
+
+int ksmodel_get_cpu(struct kshark_trace_histo *histo,
+		    int bin, int pid, bool vis_only,
+		    ssize_t *index);
+
+bool ksmodel_cpu_visible_event_exist(struct kshark_trace_histo *histo,
+				     int bin, int cpu, ssize_t *index);
+
+bool ksmodel_task_visible_event_exist(struct kshark_trace_histo *histo,
+				      int bin, int pid, ssize_t *index);
+
+static inline double ksmodel_bin_time(struct kshark_trace_histo *histo,
+				      int bin)
+{
+	return (histo->min + bin*histo->bin_size) * 1e-9;
+}
+
+static inline uint64_t ksmodel_bin_ts(struct kshark_trace_histo *histo,
+				      int bin)
+{
+	return (histo->min + bin*histo->bin_size);
+}
+
+#ifdef __cplusplus
+}
+#endif // __cplusplus
+
+#endif