Re: [LAD] A question to plugin host devs
On 12/20/20 11:59 AM, Fons Adriaensen wrote: Hello all, I wonder what are the pros and cons of using RTLD_NODELETE as a flag to dlopen() and call dlclose () as soon as the required symbols are loaded. The alternative is to leave all shared object handles open until the host terminates. What are you doing in your plugin host (and why) ? TIA, A quick search of MusE code finds no usage of it out of 21 matches on "RTLD_". Only RTLD_NOW and/or RTLD_DEFAULT. Tim. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org https://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] A question to plugin host devs
Am 20.12.20 um 19:41 schrieb Robin Gareus: Why keep it around? Guitarix is a host aimed to live performance. For performance reasons we wont load a plugin on preset switch. So, all plugs which may be used during a session been loaded already and been keep in memory. Other plugs, which are not announced cant be used without explicitly load them into the rack. Still, we don't use RTLD_NODELETE (and can't see a benefit on using it) In the distant past, Ardour (really libsuil) used NODELETE for LV2 GUIs. https://lv2plug.in/ns/extensions/ui#makeSONameResident but that is no longer the case since the option was deprecated. Wasn't that more related to the underlying libs used by plugin GUI's from the time were using shared toolkit lib's was supported (and pronounced) by the LV2 specs? So that the host don't unload for example the gtk lib's when a plugin which use it was unloaded, but a other one, which may use it as well, still is loaded? ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org https://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] A question to plugin host devs
On 12/20/20 5:59 PM, Fons Adriaensen wrote: > Hello all, > > I wonder what are the pros and cons of using RTLD_NODELETE as > a flag to dlopen() and call dlclose () as soon as the required > symbols are loaded. > > The alternative is to leave all shared object handles open until > the host terminates. Why keep it around? As soon as the last plugin instance is deleted from a session the plugin's shared object can and should be unloaded. Otherwise you would just accumulate [shared] memory simply by adding and removing different plugins. > What are you doing in your plugin host VST3 and LV2 reference implementation for Linux just use RTLD_LAZY (along with dlopen's default RTLD_LOCAL), and dlclose() when the last instance is removed. That is also what Ardour does for LV2 and VST3. I do not know any plugin host that uses RTLD_NODELETE. Besides, NODELETE is not portable. macOS' CFBundleLoadExecutable() and Windows LoadLibraryExA do not have equivalent mechanism. In the distant past, Ardour (really libsuil) used NODELETE for LV2 GUIs. https://lv2plug.in/ns/extensions/ui#makeSONameResident but that is no longer the case since the option was deprecated. > (and why) Accumulating memory generally degrades overall performance. The larger the page table, the more expensive are context switches. [Re]Loading the shared object adds overhead of static initialization, which is usually done in the GUI thread and fast compared to any user interaction. It's also a one time operation, not a periodic one. As a side-effect it also aids plugin-developers. If a host unloads the .so. A dev can recompile the plugin and reload it in the same session. Cheers! robin ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org https://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] A question to plugin host devs
Am 20.12.20 um 17:59 schrieb Fons Adriaensen: Hello all, I wonder what are the pros and cons of using RTLD_NODELETE as a flag to dlopen() and call dlclose () as soon as the required symbols are loaded. The alternative is to leave all shared object handles open until the host terminates. What are you doing in your plugin host (and why) ? TIA, In guitarix we use RTLD_LOCAL|RTLD_NOW and we only call dlclose () when the plug isn't compatible with our host, or when the host shut down. RTLD_NODELETE may have a benefit when you load/unload/load/unload/ . . . a plugin library, ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org https://lists.linuxaudio.org/listinfo/linux-audio-dev
[LAD] A question to plugin host devs
Hello all, I wonder what are the pros and cons of using RTLD_NODELETE as a flag to dlopen() and call dlclose () as soon as the required symbols are loaded. The alternative is to leave all shared object handles open until the host terminates. What are you doing in your plugin host (and why) ? TIA, -- FA ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org https://lists.linuxaudio.org/listinfo/linux-audio-dev
