79 lines
3.8 KiB
Markdown
79 lines
3.8 KiB
Markdown
# Benchmark demo
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## Overview
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The benchmark demo tests the performance in various cases.
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For example rectangle, border, shadow, text, image blending, image transformation, blending modes, etc.
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All tests are repeated with 50% opacity.
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The size and position of the objects during testing are set with a pseudo random number to make the benchmark repeatable.
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On to top of the screen the title of the current test step, and the result of the previous step is displayed.
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## Run the benchmark
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- In `lv_conf.h` or equivalent places set `LV_USE_DEMO_BENCHMARK 1`
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- After `lv_init()` and initializing the drivers call `lv_demo_benchmark()`
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- If you only want to run a specific scene for any purpose (e.g. debug, performance optimization etc.), you can call `lv_demo_benchmark_run_scene()` instead of `lv_demo_benchmark()`and pass the scene number.
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- If you enabled trace output by setting macro `LV_USE_LOG` to `1` and trace level `LV_LOG_LEVEL` to `LV_LOG_LEVEL_USER` or higher, benchmark results are printed out in `csv` format.
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## Interpret the result
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The FPS is measured like this:
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- load the next step
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- in the display driver's `monitor_cb` accumulate the time-to-render and the number of cycles
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- measure for 1 second
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- calculate `FPS = time_sum / render_cnt`
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Note that it can result in very high FPS results for simple cases.
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E.g. if some simple rectangles are drawn in 5 ms, the benchmark will tell it's 200 FPS.
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So it ignores `LV_DISP_REFR_PERIOD` which tells LVGL how often it should refresh the screen.
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In other words, the benchmark shows the FPS from the pure rendering time.
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By default, only the changed areas are refreshed. It means if only a few pixels are changed in 1 ms the benchmark will show 1000 FPS. To measure the performance with full screen refresh uncomment `lv_obj_invalidate(lv_scr_act())` in `monitor_cb()` in `lv_demo_benchmark.c`.
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If you are doing performance analysis for 2D image processing optimization, LCD latency (flushing data to LCD) introduced by `disp_flush()` might dilute the performance results of the LVGL drawing process, hence make it harder to see your optimization results (gain or loss). To avoid such problem, please:
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1. Temporarily remove the code for flushing data to LCD inside `disp_flush()`. For example:
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```c
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static void disp_flush(lv_disp_drv_t * disp_drv, const lv_area_t * area, lv_color_t * color_p)
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{
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#if 0 //!< remove LCD latency
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GLCD_DrawBitmap(area->x1, //!< x
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area->y1, //!< y
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area->x2 - area->x1 + 1, //!< width
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area->y2 - area->y1 + 1, //!< height
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(const uint8_t *)color_p);
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#endif
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/*IMPORTANT!!!
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*Inform the graphics library that you are ready with the flushing*/
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lv_disp_flush_ready(disp_drv);
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}
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```
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2. Use trace output to get the benchmark results by:
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- Setting macro `LV_USE_LOG` to `1`
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- Setting trace level `LV_LOG_LEVEL` to `LV_LOG_LEVEL_USER` or higher.
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## Result summary
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In the end, a table is created to display measured FPS values.
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On top of the summary screen, the "Weighted FPS" value is shown.
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In this, the result of the more common cases are taken into account with a higher weight.
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"Opa. speed" shows the speed of the measurements with opacity compared to full opacity.
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E.g. "Opa. speed = 90%" means that rendering with opacity is 10% slower.
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In the first section of the table, "Slow but common cases", those cases are displayed which are considered common but were slower than 20 FPS.
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Below this in the "All cases section" all the results are shown. The < 10 FPS results are shown with red, the >= 10 but < 20 FPS values are displayed with orange.
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