On Thu, Oct 22, 2020 at 03:00:13PM +1100, David Gibson wrote: > On Wed, Oct 21, 2020 at 06:49:14PM -0400, Tom Rini wrote: > > On Tue, Oct 20, 2020 at 01:09:07PM +1100, David Gibson wrote: > > > On Mon, Oct 19, 2020 at 08:37:00AM -0400, Tom Rini wrote: > > > > On Mon, Oct 19, 2020 at 12:42:13PM +1100, David Gibson wrote: > > > > > On Fri, Oct 16, 2020 at 03:46:41PM -0600, Simon Glass wrote: > > > > > > Hi Tom, > > > > > > > > > > > > On Fri, 16 Oct 2020 at 13:36, Tom Rini <trini@xxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > Hey all, > > > > > > > > > > > > > > With my U-Boot hat on, I'm trying to move us up from 84e414b0b5bc in dtc > > > > > > > to cbca977ea121. I'm seeing some rather worrying size increases > > > > > > > however. For example, on an aarch64 board such as leez-rk3399 we have: > > > > > > > leez-rk3399 : all +2696 spl/u-boot-spl:all +1116 spl/u-boot-spl:text +1116 text +2696 > > > > > > > u-boot: add: 0/0, grow: 42/0 bytes: 2696/0 (2696) > > > > > > > function old new delta > > > > > > > do_fdt 3992 4308 +316 > > > > > > > fdt_check_header 276 492 +216 > > > > > > > fdt_add_property_ 388 556 +168 > > > > > > > fdt_ro_probe_ 128 252 +124 > > > > > > > fdt_packblocks_ 176 296 +120 > > > > > > > fdt_open_into 392 512 +120 > > > > > > > fdt_blocks_misordered_ 96 216 +120 > > > > > > > fdt_get_mem_rsv 108 220 +112 > > > > > > > fdt_offset_ptr 104 208 +104 > > > > > > > fdt_get_string 288 388 +100 > > > > > > > fdt_splice_ 148 228 +80 > > > > > > > fdt_valid 204 276 +72 > > > > > > > fdt_getprop_by_offset 184 256 +72 > > > > > > > fdt_splice_mem_rsv_ 96 152 +56 > > > > > > > fdt_num_mem_rsv 60 116 +56 > > > > > > > fdt_splice_struct_ 96 144 +48 > > > > > > > fdt_shrink_to_minimum 220 268 +48 > > > > > > > fdt_rw_probe_ 108 156 +48 > > > > > > > fdt_mem_rsv 60 108 +48 > > > > > > > fdt_getprop_namelen 100 148 +48 > > > > > > > fdt_get_property_by_offset_ 100 148 +48 > > > > > > > fdt_get_name 164 212 +48 > > > > > > > efi_install_fdt 964 1012 +48 > > > > > > > boot_get_fdt 888 936 +48 > > > > > > > fdt_move 80 116 +36 > > > > > > > reserve_fdt 72 96 +24 > > > > > > > reloc_fdt 76 100 +24 > > > > > > > image_setup_libfdt 284 308 +24 > > > > > > > fit_image_load 1608 1632 +24 > > > > > > > fit_image_get_data_and_size 172 196 +24 > > > > > > > fit_get_end 16 40 +24 > > > > > > > fdt_next_tag 256 280 +24 > > > > > > > fdt_header_size 12 36 +24 > > > > > > > fdt_get_property_namelen_ 212 236 +24 > > > > > > > fdt_get_property_namelen 44 68 +24 > > > > > > > fdt_get_phandle 120 144 +24 > > > > > > > fdt_del_node 96 120 +24 > > > > > > > fdt_del_mem_rsv 112 136 +24 > > > > > > > fdt_add_subnode_namelen 284 308 +24 > > > > > > > fdt_add_mem_rsv 124 148 +24 > > > > > > > common_diskboot 680 704 +24 > > > > > > > fdt_next_subnode 80 88 +8 > > > > > > > spl-u-boot-spl: add: 1/-1, grow: 25/-2 bytes: 1176/-60 (1116) > > > > > > > function old new delta > > > > > > > fdt_get_mem_rsv 52 236 +184 > > > > > > > fdt_add_property_ 340 484 +144 > > > > > > > fdt_get_name 68 152 +84 > > > > > > > fdt_splice_ 148 228 +80 > > > > > > > fdt_num_mem_rsv 64 128 +64 > > > > > > > fdt_splice_mem_rsv_ 96 152 +56 > > > > > > > fdt_offset_ptr 52 104 +52 > > > > > > > fdt_splice_struct_ 96 144 +48 > > > > > > > fdt_shrink_to_minimum 220 268 +48 > > > > > > > fdt_get_property_by_offset_ 36 84 +48 > > > > > > > fdt_ro_probe_ - 36 +36 > > > > > > > fdt_subnode_offset_namelen 200 232 +32 > > > > > > > spl_load_simple_fit 848 872 +24 > > > > > > > spl_fit_append_fdt 196 220 +24 > > > > > > > fdt_getprop_by_offset 80 104 +24 > > > > > > > fdt_get_string 64 88 +24 > > > > > > > fdt_get_property_namelen_ 200 224 +24 > > > > > > > fdt_get_phandle 120 144 +24 > > > > > > > fdt_del_mem_rsv 104 128 +24 > > > > > > > fdt_check_header 28 52 +24 > > > > > > > fdt_add_subnode_namelen 260 284 +24 > > > > > > > fdt_add_mem_rsv 112 136 +24 > > > > > > > fdt_next_tag 192 212 +20 > > > > > > > fdt_path_offset_namelen 240 256 +16 > > > > > > > fdt_supernode_atdepth_offset 160 172 +12 > > > > > > > fdt_node_offset_by_phandle 120 132 +12 > > > > > > > fdt_mem_rsv 20 - -20 > > > > > > > fdt_check_prop_offset_ 64 44 -20 > > > > > > > fdt_check_node_offset_ 64 44 -20 > > > > > > > > > > > > > > And note that for the SPL case we're already setting ASSUME_MASK to > > > > > > > 0xff so there's maximum savings already being done there. Does anyone > > > > > > > have ideas on where / how to further tweak code size? Thanks! > > > > > > > > > > > > +David Gibson > > > > > > > > > > > > I suspect there are more checks that need to be made conditional. > > > > > > > > > > Seems likely. > > > > > > > > OK. Does that mean you're going to take a look? > > > > > > No, sorry, my time for dtc is very limited. > > > > OK, fair point. > > > > > > > Though, as I've opined before, from what I understand the SPL is *so* > > > > > restricted an environment, I'm not really convinced DTs are the right > > > > > tool for the job there. > > > > > > > > SPL is space constrained, which is why we mask out all of the safety > > > > checks. But we still generally have enough memory that this is fine. > > > > This specific board has 256KiB for SPL, for example. But I'm not just > > > > concerned about 1KiB of growth when everything is masked off, I'm also > > > > concerned about 2KiB of growth over a changelog that doesn't read like > > > > it added a bunch of stuff that should cause everything to grow, > > > > either. > > > > > > Yeah, that's a good point. It's certainly not obvious to me what > > > would have caused the growth. I think we'll need a revision by > > > revision test to see where it was added. > > > > So, with a bit of playing around, I've used buildman to give us that, > > for the leez-rk3399 platform. The full results are at > > https://gist.github.com/trini/e42cc848d38bfc77e0124d3ace86d95d and note > > that build #6, "scripts/dtc: Update to upstream version > > v1.4.6-22-g24b1f3f064d4" is the first interesting one (#5 was a resync > > entirely to dtc's 84e414b0b5bc rather than strictly what U-Boot has). > > Right.. I was meaning stepping through the dtc upstream revisions, not > just the uboot revisions, so you get a fine grained idea of where the > increase is coming from. Yes, that's what that link is. I imported every revision from point A to point B, and built U-Boot for it, and checked the sizes, since we have tooling for that. It's possible the bloat-o-meter script in the kernel could be used, but I'm not sure what the right target(s) in dtc would be, to get any useful information out. > > But what does all of this _mean_ ? I kinda think I have an answer now. > > One of the things that sticks out is 6dcb8ba408ec adds a lot and > > 11738cf01f15 reduces it just a little. > > Ah, that's a tricky one. If we don't handle unaligned accesses we > instead get intermittent bug reports where it just crashes. We really need to talk about that then. There was a problem of people turning off the sanity check for making sure the entire device tree was aligned and then having everything crash. > I suppose we could add an ASSUME_ALIGNED_ACCESS flag, and it will just > break for either an unaligned dtb (unlikely) or if you attempt to load > an unaligned value from a property (more likely, but don't add the > flag if you're not sure you don't need it). So long as it's abstracted in such a way that we don't grow the size of everything again, yes, that is the right way forward I think. These tests still introduce a big boot-time slowdown as well. > > With a re-revert again locally, there's just a few size > > growths now to look in to on the SPL side: > > leez-rk3399 : all +8 spl/u-boot-spl:all +180 spl/u-boot-spl:text +180 text +8 > > u-boot: add: 0/0, grow: 3/-1 bytes: 28/-20 (8) > > function old new delta > > fdt_move 80 92 +12 > > fdt_splice_ 148 156 +8 > > fdt_offset_ptr 104 112 +8 > > fdt_get_string 288 268 -20 > > spl-u-boot-spl: add: 1/0, grow: 9/-2 bytes: 220/-40 (180) > > function old new delta > > fdt_get_name 68 128 +60 > > fdt_get_mem_rsv 52 96 +44 > > fdt_subnode_offset_namelen 200 232 +32 > > fdt_next_tag 192 212 +20 > > fdt_path_offset_namelen 240 256 +16 > > fdt_supernode_atdepth_offset 160 172 +12 > > fdt_ro_probe_ - 12 +12 > > fdt_node_offset_by_phandle 120 132 +12 > > fdt_splice_ 148 156 +8 > > fdt_offset_ptr 52 56 +4 > > fdt_check_prop_offset_ 64 44 -20 > > fdt_check_node_offset_ 64 44 -20 > > > > Of those, I'm not 100% sure. That might well end up being Simon's > > suggestion of a few places needing a check they don't have, I'm not > > sure. > > Maybe. Really need to know which dtc/libfdt revision makes the > changes to decipher that. Yes, there's a few suggestive dtc revisions that change the size of those functions in the full gist. I think some of the satisfy Coverity changes had small impact, but I didn't look for fdt_get_name / fdt_get_mem_rsv. -- Tom
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