i915-perf: set a different default colors to GPU timeline events

By default we're currently using the same color for all GPU timeline
events. But some i915 driver versions don't have tracepoint support to
build correlation back to the process that submitted the work, so that
we can use the process' color.

So just assign a default color so that we can at least tell items
apart on the timeline.

src/gpuvis.cpp

@@ -2162,13 +2162,36 @@ void TraceEvents::init_i915_perf_event( trace_event_t &event )
 
 void TraceEvents::update_i915_perf_colors()
 {
+    // The pid field of i915-perf events is the GPU context ID. Assign each of
+    // them a color in case we can't find a process related to them.
+    std::unordered_set< int > all_gpu_contexts;
+    for ( const uint32_t event_id : m_i915.perf_locs )
+    {
+        const trace_event_t &i915_perf_event = m_events[ event_id ];
+
+        if ( all_gpu_contexts.find( i915_perf_event.pid ) == all_gpu_contexts.end() )
+            all_gpu_contexts.insert( i915_perf_event.pid );
+    }
+
+    uint32_t idx = 0;
+    std::map< int, uint32_t > gpu_context_to_color;
+    for ( auto context_id : all_gpu_contexts )
+    {
+        ImVec4 color( 0.0f, 0.0f, 0.0f, 1.0f );
+        ImGui::ColorConvertHSVtoRGB( (float) idx++ / all_gpu_contexts.size(), 1.0, 0.5,
+                                     color.x, color.y, color.z );
+        gpu_context_to_color.insert( std::make_pair( context_id, ImGui::ColorConvertFloat4ToU32( color ) ) );
+    }
+
+    // Go through all i915-perf events and assign the color of the process
+    // that submitted the workload to the GPU timeline event.
     for ( const uint32_t event_id : m_i915.perf_locs )
     {
         trace_event_t &i915_perf_event = m_events[ event_id ];
 
         if ( m_i915.perf_to_req_in.m_map.find( i915_perf_event.id ) == m_i915.perf_to_req_in.m_map.end() )
         {
-            i915_perf_event.color = s_clrs().get( col_Graph_Bari915Execute );
+            i915_perf_event.color = gpu_context_to_color[ i915_perf_event.pid ];
         }
         else
         {

src/gpuvis_colors.inl

@@ -68,7 +68,6 @@ _XTAG( col_Graph_TaskRunning, 0x4fff00ff, "Sched_switch task running block" )
 _XTAG( col_Graph_TaskSleeping, 0x4fffff00, "Sched_switch task sleeping block" )
 
 _XTAG( col_Graph_Bari915ReqWait, 0x4f0000ff, "i915 reqwait bar" )
-_XTAG( col_Graph_i915Perf, 0xff9b9400, "i915-perf bar" )
 
 _XTAG( col_Graph_Bari915Queue, 0xc81d740c, "Request queued waiting to be added" )
 _XTAG( col_Graph_Bari915SubmitDelay, 0xc8f8552e, "Requests waiting on fences and dependencies before they are runnable" )

src/gpuvis_i915_perfcounters.cpp

@@ -191,7 +191,7 @@ I915PerfCounters::get_process( const trace_event_t &i915_perf_event )
 {
     i915_perf_process process;
     process.label = "<unknown>";
-    process.color = s_clrs().get( col_Graph_i915Perf );
+    process.color = i915_perf_event.color;
 
     uint32_t *req_event_id = m_trace_events->m_i915.perf_to_req_in.get_val( i915_perf_event.id );