Esta semana me he topado con una evolución en los comentarios de código: comentarios con ascii art.
/* This function is based on the current VRAM usage.
*
* - If all of VRAM is free, allow relocating the number of bytes that
* is equal to 1/4 of the size of VRAM for this IB.
* - If more than one half of VRAM is occupied, only allow relocating
* 1 MB of data for this IB.
*
* - From 0 to one half of used VRAM, the threshold decreases
* linearly.
* __________________
* 1/4 of -|\ |
* VRAM | \ |
* | \ |
* | \ |
* | \ |
* | \ |
* | \ |
* | \________|1 MB
* |----------------|
* VRAM 0 % 100 %
* used used
*
* Note: It's a threshold, not a limit. The threshold must be crossed
* for buffer relocations to stop, so any buffer of an arbitrary size
* can be moved as long as the threshold isn't crossed before
* the relocation takes place. We don't want to disable buffer
* relocations completely.
*
* The idea is that buffers should be placed in VRAM at creation time
* and TTM should only do a minimum number of relocations during
* command submission. In practice, you need to submit at least
* a dozen IBs to move all buffers to VRAM if they are in GTT.
*
* Also, things can get pretty crazy under memory pressure and actual
* VRAM usage can change a lot, so playing safe even at 50% does
* consistently increase performance.
*/
El que quiera ver el código completo lo puede hacer en
este parche de Marek Olšák para Radeon, el driver para Linux las tarjetas gráficas de AMD.