102 lines
5.2 KiB
Markdown
102 lines
5.2 KiB
Markdown
# Logging, frame rate and performance metrics
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## 1.0) Logging of potentially dangerous actions
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OpenTTD is a complex program, and together with NewGRF, it may show a buggy
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behaviour. But not only bugs in code can cause problems. There are several
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ways to affect game state possibly resulting in program crash or multiplayer
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desyncs.
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Easier way would be to forbid all these unsafe actions, but that would affect
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game usability for many players. We certainly do not want that.
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However, we receive bug reports because of this. To reduce time spent with
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solving these problems, these potentially unsafe actions are logged in
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the savegame (including crash.sav). Log is stored in crash logs, too.
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Information logged:
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- Adding / removing / changing order of NewGRFs
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- Changing NewGRF parameters, loading compatible NewGRF
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- Changing game mode (scenario editor <-> normal game)
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- Loading game saved in a different OpenTTD / TTDPatch / Transport Tycoon Deluxe /
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original Transport Tycoon version
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- Running a modified OpenTTD build
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- Changing settings affecting NewGRF behaviour (non-network-safe settings)
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- Triggering NewGRF bugs
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No personal information is stored.
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You can show the game log by typing 'gamelog' in the console or by running
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OpenTTD in debug mode.
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## 2.0) Frame rate and performance metrics
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The Help menu in-game has a function to open the Frame rate window. This
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window shows various real-time performance statistics, measuring what parts
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of the game require the most processing power currently.
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A summary of the statistics can also be retrieved from the console with the
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`fps` command. This is especially useful on dedicated servers, where the
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administrator might want to determine what's limiting performance in a slow
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game.
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The frame rate is given as two figures, the simulation rate and the graphics
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frame rate. Usually these are identical, as the screen is rendered exactly
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once per simulated tick, but in the future there might be support for graphics
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and simulation running at different rates. When the game is paused, the
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simulation rate drops to zero.
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In addition to the simulation rate, a game speed factor is also calculated.
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This is based on the target simulation speed, which is 30 milliseconds per
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game tick. At that speed, the expected frame rate is 33.33 frames/second, and
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the game speed factor is how close to that target the actual rate is. When
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the game is in fast forward mode, the game speed factor shows how much
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speed up is achieved.
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The lower part of the window shows timing statistics for individual parts of
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the game. The times shown are short-term and long-term averages of how long
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it takes to process one tick of game time, all figures are in milliseconds.
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Clicking a line in the lower part of the window opens a graph window, giving
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detailed readings on each tick simulated by the game.
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The following is an explanation of the different statistics:
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- *Game loop* - Total processing time used per simulated "tick" in the game.
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This includes all pathfinding, world updates, and economy handling.
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- *Cargo handling* - Time spent loading/unloading cargo at stations, and
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industries and towns sending/retrieving cargo from stations.
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- *Train ticks*, *Road vehicle ticks*, *Ship ticks*, *Aircraft ticks* -
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Time spent on pathfinding and other processing for each player vehicle type.
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- *World ticks* - Time spent on other world/landscape processing. This
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includes towns growing, building animations, updates of farmland and trees,
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and station rating updates.
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- *GS/AI total*, *Game script*, and *AI players* - Time spent running logic
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for game scripts and AI players. The total may show as less than the current
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sum of the individual scripts, this is because AI players at lower
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difficulty settings do not run every game tick, and hence contribute less
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to the average across all ticks. Keep in mind that the "Current" figure is
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also an average, just only over short term.
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- *Link graph delay* - Time overruns of the cargo distribution link graph
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update thread. Usually the link graph is updated in a background thread,
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but these updates need to synchronise with the main game loop occasionally,
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if the time spent on link graph updates is longer than the time taken to
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otherwise simulate the game while it was updating, these delays are counted
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in this figure.
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- *Graphics rendering* - Total time spent rendering all graphics, including
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both GUI and world viewports. This typically spikes when panning the view
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around, and when more things are happening on screen at once.
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- *World viewport rendering* - Isolated time spent rendering just world
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viewports. If this figure is significantly lower than the total graphics
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rendering time, most time is spent rendering GUI than rendering world.
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- *Video output* - Speed of copying the rendered graphics to the display
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adapter. Usually this should be very fast (in the range of 0-3 ms), large
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values for this can indicate a graphics driver problem.
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- *Sound mixing* - Speed of mixing active audio samples together. Usually
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this should be very fast (in the range of 0-3 ms), if it is slow, consider
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switching to the NoSound set.
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If the frame rate window is shaded, the title bar will instead show just the
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current simulation rate and the game speed factor.
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