<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED NOTABUG - Performance improvement : Please consider hardware ɢᴘᴜ rendering in llvmpipe" href="https://bugs.freedesktop.org/show_bug.cgi?id=93686#c24">Comment # 24</a> on <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED NOTABUG - Performance improvement : Please consider hardware ɢᴘᴜ rendering in llvmpipe" href="https://bugs.freedesktop.org/show_bug.cgi?id=93686">bug 93686</a> from <a class="email" href="mailto:alexdeucher@gmail.com" title="Alex Deucher <alexdeucher@gmail.com>"> Alex Deucher</a> <pre>(In reply to ytrezq from <a href="show_bug.cgi?id=93686#c15">comment #15</a>) > (In reply to Alex Deucher from <a href="show_bug.cgi?id=93686#c13">comment #13</a>) > > I can't speak for intel, but on AMD APUs, while the GPU appears as a device > > on the PCIE bus, it actually has a much faster internal connection to the > > memory controller. > You’re still confusing things. Of course they use the same memory controller > directly. Of course they share the same memory modules. > However they can’t read or write in memory of each others. So this behave > like an external card ᴘᴄɪe card with it’s own memory modules (if we forget > the bandwidth is also shared with an another device so each ones slow each > others). > > So if you want to send or receive data it can only happens over the ᴘᴄɪe > bus, triggering the same synchronisations problems of external chipsets due > to the bus bandwidth and instructions overhead. > > Unified memory will only happen in future generations of graphics cards, but > only behind a ᴘᴄɪe bus (which will slow things because there’s still the > memory controller bus adding overhead), so we’re far from the time were ɢᴘᴜs > of ᴀᴘᴜs will be able to access ʀᴀᴍ of ᴄᴘᴜs with the same overhead (at that > time it’s expected ʀᴀᴍ modules would have been merged into the ᴄᴘᴜ chip > meaning there would be no longer separated ʀᴀᴍ modules). No, it happens right now. The stolen memory used for APU "vram" is mainly for vbios splash screen post messages to minimize the amount of gpu setup required in the vbios and to provide contiguous memory which is slightly faster than going through an MMU. Once the APU driver has initialized it can map system memory directly via the GPU's MMU. Access to that memory does not go over the pcie bus. The GPU has a direct internal link the system memory similar to what the CPU has.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>