On Wed, Feb 5, 2025 at 3:29 AM Charlie Jenkins <charlie@xxxxxxxxxxxx> wrote: > > On Tue, Feb 04, 2025 at 01:04:26PM +0900, Masahiro Yamada wrote: > > On Sat, Feb 1, 2025 at 6:33 AM Charlie Jenkins <charlie@xxxxxxxxxxxx> wrote: > > > > > > On Sat, Feb 01, 2025 at 12:10:02AM +0900, Masahiro Yamada wrote: > > > > On Fri, Jan 31, 2025 at 3:54 PM Charlie Jenkins <charlie@xxxxxxxxxxxx> wrote: > > > > > > > > > > On Thu, Jan 30, 2025 at 08:52:45PM -0700, Nathan Chancellor wrote: > > > > > > On Wed, Jan 22, 2025 at 07:17:26PM -0800, Charlie Jenkins wrote: > > > > > > > On riscv, kernel modules end up with a significant number of local > > > > > > > symbols. This becomes apparent when compiling modules with debug symbols > > > > > > > enabled. Using amdgpu.ko as an example of a large module, on riscv the > > > > > > > size is 754MB (no stripping), 53MB (--strip-debug), and 21MB > > > > > > > (--strip-unneeded). ON x86, amdgpu.ko is 482MB (no stripping), 21MB > > > > > > > (--strip-debug), and 20MB (--strip-unneeded). > > > > > > > > > > > > > > Use --strip-unneeded instead of --strip-debug to strip modules so > > > > > > > decrease the size of the resulting modules. This is particularly > > > > > > > relevant for riscv, but also marginally aids other architectures. > > > > > > > > > > > > > > Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx> > > > > > > > > > > > > Is there any sort of regression risk with this patch? If so, another > > > > > > option may be to give another level to INSTALL_MOD_STRIP like 2 so that > > > > > > INSTALL_MOD_STRIP=1 continues to behave as before but people can easily > > > > > > opt into this option. No strong opinion because I am not sure but was > > > > > > not sure if it was considered. > > > > > > > > > > I do not believe this would cause regressions. The description on gnu > > > > > strip is: > > > > > > > > > > "Remove all symbols that are not needed for relocation processing in > > > > > addition to debugging symbols and sections stripped by --strip-debug." > > > > > > > > > > The description on llvm-strip is: > > > > > > > > > > "Remove from the output all local or undefined symbols that are not > > > > > required by relocations. Also remove all debug sections." > > > > > > > > > > gnu strip --strip-unneeded strips slightly more aggressively but it does > > > > > not appear this causes any issues. > > > > > > > > > > > > > > > > > Regardless: > > > > > > > > > > > > Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > > > > > > > > > Thanks! > > > > > > > > > > > > > > > > > It is true --strip-unneeded drops a lot of compiler-generated symbols, but > > > > it also drops real symbols that originate in the source code. > > > > > > > > So, this would give user-visible changes for kallsyms at least. > > > > > > Adding INSTALL_MOD_STRIP="--strip-unneeded" would be sufficient for > > > riscv. However, this has the downside that riscv will require different > > > flags than other architectures to get reasonably sized modules. > > > > You can use INSTALL_MOD_STRIP=--strip-unneeded for all architecture if you like. > > > > I assume this is a riscv issue. Specifically, riscv gcc. > > With LLVM=1, I see much smaller riscv modules using INSTALL_MOD_STRIP=1. > > > > --strip-unneeded is needlessly aggressive for other architectures, > > and I do not see a good reason to change the default. > > Yes it is primarily an issue with riscv GCC. I was hoping for something > more standardized so that other people using riscv GCC wouldn't > encounter this. Would it be reasonable to add this flag by default only > for the riscv architecture, or do you think it's just better to leave it > up to the user's choice? The latter. INSTALL_MOD_STRIP=1 passes --strip-debug. This is clearly documented in Documentation/kbuild/makefiles.rst and it has worked like that for many years, with no exception. If users want it to work differently, the flexibility is already there. If INSTALL_MOD_STRIP=1 worked differently, silently only for riscv, I would regard it as insane behavior. -- Best Regards Masahiro Yamada
