Strip useless debug sections from binaries, to make them smaller. #2514
Conversation
hlinnaka
force-pushed
the
strip-pubnames
branch
5 times, most recently
from
924b12b to
efbda71
Compare
|
The strip-step takes about 90 seconds, which is more than I hoped. Might still be worthwhile. Or maybe do this only for the larger binaries or some other such compromise. |
There was a problem hiding this comment.
LGTM, I like the lesser size despite the drastic time increase, and I think we should add the same for the Docker builds: 1.5mins added to already existing ~30 mins is not huge, but we allow to download ~30% less data, which happens more frequently than builds.
I've also noticed that most of the time is consumed by the last command:
find target -executable -type f -links +1 ! -name "*.lock" | xargs -IPATH objcopy -R .debug_pubnames -R .debug_pubtypes -p PATH
I wonder, how much do we remove without it, maybe it's already enough.
hlinnaka
force-pushed
the
strip-pubnames
branch
from
efbda71 to
7471a47
Compare
|
I wasn't happy with the added 1.5 minutes, so I spent a little more time on this. I replaced the "find | xargs" commands with a little python script. It understands hard links and knows not to invoke two objcopy's on the same hardlinked file, which allows more processes to run in parallel. This runs in 30 s on my laptop now, let's see how fast it is in the CI. |
|
1m 46s, most of the time seems to be spent on
|
The rust compiler or linker (I'm not sure which) emits .debug_pubnames and .debug_pubtypes sections in the binaries. They are supposed to speed up launching a debugger, but they're obsolete. They've been superseded by .debug_names section in more recent DWARF spec and debuggers, and gdb and lldb just ignores them. I could not find any way to prevent rustc / ldb / mold from emitting these sections in the first place. So this commit adds a hack to strip them off afterwards. This makes the binaries about 30% smaller, with the downside of adding about 30 s to the build time in CI. That seems like a good tradeoff, as smaller binaries can speed up other steps.
hlinnaka
force-pushed
the
strip-pubnames
branch
from
7471a47 to
004b6bb
Compare
|
Related: #2803 |
|
As discussed moving to draft |
|
There's a new proposal on rustc to stop emitting these: rust-lang/compiler-team#688 |
|
This was fixed in rustc 1.76.0, it no longer generates the useless (Our binaries are still huge, but for different reasons) |
The rust compiler or linker (I'm not sure which) emits .debug_pubnames and .debug_pubtypes sections in the binaries. They are supposed to speed up launching a debugger, but they're obsolete. They've been superseded by .debug_names section in more recent DWARF spec and debuggers, and gdb and lldb just ignores them.
I could not find any way to prevent rustc / ldb / mold from emitting these sections in the first place. So this commit adds a hack to strip them off afterwards. This makes the binaries about 30% smaller, for no apparent downside.