On Thu, May 18, 2023 at 07:41:17AM -0700, Palmer Dabbelt wrote: > On Thu, 18 May 2023 07:06:17 PDT (-0700), Conor Dooley wrote: > > On Thu, May 18, 2023 at 07:13:15PM +0530, Anup Patel wrote: > > > On Thu, May 18, 2023 at 4:02 PM Andrew Jones <ajones@xxxxxxxxxxxxxxxx> wrote: > > > > On Thu, May 18, 2023 at 09:58:30AM +0100, Conor Dooley wrote: > > > One downside of this new approach is it will increase the size of DTB. > > > Imaging 50 such DT properties in 46 CPU DT nodes. > > > > I should do a comparison between 50 extensions in riscv,isa and doing > > this 50 times and see what the sizes are. > > I'm not sure how sensitive people are to DT size (presumably it'd be DTB > size)? > > It's also not clear what we can do about it: RISC-V has lots of extensions, > that's going to take encoding space. Sticking with an ambiguous encoding > because it's smaller seems like a way to get burned in the long run. I did actually go an look at this. I cheated a little and renamed the properties to "riscv,isa-ext-foo", which is about as communicative IMO as the longer name I currently have, but may seem more agreeable to the size conscious. I added 30 cpu nodes to mpfs.dtsi, each with 100 extensions of 6 chars long. With just the string, containing "rv64imafdc_zabcde_...", it was unreadable, but "only" took up 46k. I then removed the multiletter extensions from riscv,isa & switched to riscv,isa-base & 100 booleans. IMO it was more readable (although still quite bad!), but took up 62k. Removing all of the boolean properties, leaving me with 30 addtional harts with "rv64imafdc" only, was 26k. I think the generic limit for dtb files is 2 MiB? To me the size increase doesn't sound like a bit problem.
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