On Fri, 23 Jun 2017 10:31:28 +0200 Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote: > On Fri, 2017-06-23 at 15:49 +0800, Zhi Wang wrote: > > Hi: > > Thanks for the discussions! If the userspace application has > > already maintained a LRU list, it looks like we don't need > > generation > > anymore, > > generation isn't required, things are working just fine without that. > It is just a small optimization, userspace can skip the LRU lookup > altogether if the generation didn't change. > > But of couse that only pays off if the kernel doesn't has to put much > effort into maintaining the generation id. Something simple like > increasing it each time the guest writes a register which affects > plane_info. But it seems like that simple management algorithm pretty much guarantees that the kernel will never revisit a generation and therefore caching dmabuf fds is pointless. AIUI the optimization is to allow userspace to 'at a glance' test one plane_info vs another. The user could also do this with a memcmp of the plane_info structs if that's its only purpose. A randomly incremented field within that struct could actually be a hindrance to the user for such a comparison. Are there cases where the plane_info struct is otherwise identical where the user would need to get a new dmabuf fd anyway? Thanks, Alex _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
