On Wed, Apr 05, 2017 at 04:38:25PM +0100, Emil Velikov wrote: > Hi Ken, > > On 5 April 2017 at 01:09, Kenneth Graunke <kenn...@whitecape.org> wrote: > > Hello, > > > > This series imports libdrm_intel into the i965 driver, hacks and > > slashes it down to size, and greatly simplifies our relocation > > handling. > > > > Some of the patches may be held for moderation. You can find the > > series in git here: > > > > https://cgit.freedesktop.org/~kwg/mesa/log/?h=bacondrm > > > > A couple of us have been talking about this in person and IRC for > > a while, but I realize I haven't mentioned anything about it on the > > mailing list yet, so this may come as a bit of a surprise. > > > > libdrm_intel is about 15 source files and almost 13,000 lines of code. > > This series adds 3 files (one .c, two .h) and only 2,137 lines of code: > > > > 60 files changed, 2784 insertions(+), 647 deletions(-) > > > > The rest of the library is basically useless to us. It contains a lot > > of legacy cruft from the pre-GEM, DRI1, or 8xx/9xx era. But even the > > parts we do use are in bad shape. BO offset tracking is non-threadsafe. > > Relocation handling is way too complicated. These things waste memory, > > burn CPU time, and make it difficult for us to take advantage of new > > kernel features like I915_EXEC_NO_RELOC which would reduce overhead > > further. The unsynchronized mapping API performs a synchronized mapping > > on non-LLC platforms, which can massively hurt performance on Atoms. > > Mesa is also using uncached GTT mappings for almost everything on Atoms, > > rather than fast CPU or WC maps where possible. > > > > Evolving this code in libdrm is very painful, as we aren't allowed to > > break the ABI. All the legacy cruft and design mistakes (in hindsight) > > make it difficult to follow what's going on. We could keep piling new > > layers on top, but that only makes it worse. Furthermore, there's a > > bunch of complexity that comes from defending against or supporting > > broken or badly designed callers. > > > I believe I mentioned it a few days ago - there is no need to worry > about API or ABI stability. > > Need new API - add it. Things getting fragile or too many layers - sed > /libdrm_intel$(N)/libdrm_intel$(N+1)/ and rework as needed. > > I fear that Importing libdrm_intel will be detrimental to libva's > intel-driver, Beignet and xf86-video-intel development. > Those teams seem to be more resource contained than Mesa, thus they > will trail behind even more. > > As an example - the intel-driver is missing some trivial winsys > optimisations that landed in Mesa 3+ years ago. That could have been > avoided if the helpers were shared with the help of > libdrm_intel/other.
That is kinda the longer-term goal with this. There's a lot more that needs to be done besides Ken's series here, this is just the first step, but in the end we'll probably move brw_batch back into libdrm_intel2 or so, for consumption by beignet and libva. But for rewriting the world and getting rid of 10+ years of compat garbage, having a split between libdrm and mesa isn't great. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
