Downsides of force_gl_names_reuse preventing adoption as default

[Marek Olšák]

https://gitlab.freedesktop.org/mareko/mesa/-/commit/cdde6fcb7947514753c1a3feaee71c2212cffea6

If I remember correctly, it failed some tests.

Marek

On Thu, Oct 3, 2024 at 3:53 AM Rocco Tormenta <rocco at tormenta.eu> wrote:
>
> Hi there, apologies if this has already been asked, I couldn't find
> relevant information on the matter.
>
> Recently I've come across some faulty applications (notably, old
> Minecraft versions) that were calling `glBind*` functions with IDs of
> -1, resulting in very slow performance due to the hash table defaulting
> to full lookups.
>
> Skimming through the source code I've noticed that a while ago, name
> reusing/sparse names were implemented using idalloc (see MR
> mesa/mesa!6600), locked behind a config flag. Indeed, setting the
> force_gl_names_reuse=true environment variable fixes the performance issue.
>
> The comment on the MR that added this feature mentions that this
> behavior is in line with that of major proprietary drivers, so I was
> wondering why this was added as an optional flag, instead of making it
> the default behavior. I did find some potential reasons that could have
> blocked the transition back when it was merged, though. For example,
> more recently a commit was made (MR mesa/mesa!30106) lowering virtual
> memory usage of the idalloc approach from 512MB to 512KB in the
> worst-case scenario, so perhaps the higher memory footpring might have
> discouraged adoption at the beginning. With such low requirements now,
> however, perhaps it's worth reconsidering the default choice to benefit
> from higher robustness against misuse of the API.
>
> Is there anything I missed?
>
> Rocco
>