On Wed, Apr 5, 2017 at 2:03 PM, Emil Velikov <emil.l.veli...@gmail.com> wrote: > On 5 April 2017 at 18:55, Daniel Vetter <dan...@ffwll.ch> wrote: >> 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. >> > So the goal is to have the code in mesa as a form of incubator until > it reaches maturity. > This way one will have a more rapid development and greater > flexibility during that stage. > > If I misunderstood you correctly and the above sounds right - then the > idea is amazing. > Silly me did not click while reading the summary email.
This is sort of indirectly what we did for radeon. We basically abandoned libdrm_radeon in mesa and wrote our own winsys, then that, more or less, because the basis for libdrm_amdgpu. Alex _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
