Quoting Jani Nikula (2018-02-09 11:49:16) > On Thu, 08 Feb 2018, Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> wrote: > > Quoting Tvrtko Ursulin (2018-02-08 16:06:41) > >> > >> On 08/02/2018 13:26, Chris Wilson wrote: > >> > Quoting Tvrtko Ursulin (2018-02-08 13:05:51) > >> >> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > >> >> > >> >> For Joonas basically. :) > >> >> > >> >> Rough goal - add Kconfig options to turn off supported platforms > >> >> and count on compiler DCE to make the driver smaller. > >> >> > >> >> Tested as so much that it boots and renders on Skylake with all > >> >> platforms/gens older than Gen8 turned off. > >> >> > >> >> text data bss dec hex filename > >> >> 1502847 54223 2888 1559958 17cd96 i915.ko.original > >> >> 1375647 51939 2888 1430474 15d3ca i915.ko.gen8+ > >> >> > >> >> So only ~124kiB saving. Or ~8.5%. Perhaps once GCC LTO support > >> >> lands it would be better than this? > >> > > >> > Did you get to the point where the compiler was complaining about > >> > unused functions? > >> > >> No, but on a random check it seems that it is removing some. For > >> instance i965_emit_bb_start and i830_emit_bb_start are not in my > >> build. > >> > >> Doesn't mean I haven't made some other mistake which is preventing > >> more savings. > >> > >> >> Starts with smaller patches to show the idea step by step on Gen2, > >> >> then proceeds in larger chunks, to finish with some invasive > >> >> Coccinelle works to enable the last few kilo-bytes of savings. > >> > > >> > So, if we want to support this, how do we test it? > >> > > >> > Do a per-platform build and check modinfo for pci ids? > >> > > >> > Limit the CI builds to be per-platform and check they work? > >> > >> Extensively. :) Which will probably be a problem. PCI ids is not > >> enough, I think it would actually need functional testing so a growth > >> of number of builds we would need to test. > > > > My original suggestion was to be able to "pre-select the PCI ID" and > > let the compiler do the magic with LTO to get rid of the dead > > code. You would test by comparing the "include all" and "one PCI ID" > > kernel operation on same system. I'm assuming that the feature would > > be a useful non-default to opt-in to similarly to a "targeted" initrd. > > So I can imagine someone shipping a specific product with a specific > platform (or even PCI ID) could use this. Beyond that, who would use > this? Some rare enthusiasts? > > Is there any way a general purpose distro could use it? I guess only by > building several drivers with different options (and names) that would > have different PCI ID matches. The way I see this effort scaling to general purpose distros is basically with a flock of modules (or a fat module with disposable .sections). I'm a few steps sort of $profit. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
