pon., 17 wrz 2018 o 18:24 Michel Dänzer <mic...@daenzer.net> napisał(a): > > On 2018-09-15 3:04 a.m., Marek Olšák wrote: > > On Fri, Sep 14, 2018 at 4:53 AM, Michel Dänzer <mic...@daenzer.net> wrote: > >> On 2018-09-13 8:56 p.m., Marek Olšák wrote: > >> > >>> + * What happens if a driver is unloaded and the app creates a thread? > >> > >> I suppose the child process will likely crash, because the memory > >> address where util_set_full_cpu_affinity was located will either be > >> unmapped or have random other contents? > >> > >> At least in theory, there could also be an issue where the application > >> might have set its own thread affinity before calling fork, which would > >> be clobbered by util_set_full_cpu_affinity in the child process. > >> > >> > >> Last but not least, this doesn't solve the issue of apps such as > >> blender, which spawn their own worker threads after initializing OpenGL > >> (possibly not themselves directly, but via the toolkit or another > >> library; e.g. GTK+4 uses OpenGL by default), inheriting the thread > >> affinity. > >> > >> > >> Due to these issues, setting the thread affinity needs to be disabled by > >> default, and only white-listed for applications where it's known safe > >> and beneficial. This sucks, but I'm afraid that's the reality until > >> there's better API available which allows solving these issues. > > > > We don't have the bandwidth to maintain whitelists. This will either > > have to be always on or always off. > > > > On the positive side, only Ryzens with multiple CCXs get all the > > benefits and disadvantages. > > In other words, only people who spent relatively large amounts of money > for relatively high-end CPUs will be affected (I'm sure they'll be glad > to know that "common people" aren't affected. ;). Affected applications > will see their performance decreased by a factor of 2-8 (the number of > CCXs in the CPU). > > OTOH, only a relatively small number of games will get a significant > benefit from the thread affinity, and the benefit will be smaller than a > factor of 2. This cannot justify risking a performance drop of up to a > factor of 8, no matter how small the risk. > > Therefore, the appropriate mechanism is a whitelist. > > > -- > Earthling Michel Dänzer | http://www.amd.com > Libre software enthusiast | Mesa and X developer > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
Hi, What was the conclusion of this discussion? I don't see any whitelist/blacklist for this feature. I have just tested blender and it still renders on only a single CCX on mesa from git master. Also, there is a bug report that suggests this regressed performance in at least one game [1]. If you think enabling it by default is the way to go, we should also implement a blacklist so that it can be turned off in such cases. Regards, Gustaw Smolarczyk [1] https://bugs.freedesktop.org/show_bug.cgi?id=108330 _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
