On 2019-01-24 14:17, Florian Weimer wrote:
* Martin Buchholz:
Here's an experiment using the 3 competing open source linkers to link
hotspot. This confirms that lld is faster than gold is faster than
bfd, but is the one second saving worth the engineering effort?
$ (BUILDDIR=$HOME/ws/jdk/build/linux-x86_64-server-release; for
linker in bfd gold lld; do echo --- $linker ---; time /usr/bin/g++
-fuse-ld=$linker -Wl,--hash-style=both -Wl,-z,defs -Wl,-z,noexecstack
-Wl,-O1 -Wl,-z,relro -m64 -static-libstdc++ -static-libgcc -shared
-m64 -Wl,-version-script=$BUILDDIR/hotspot/variant-server/libjvm/mapfile
-Wl,-soname=libjvm.so -o
$BUILDDIR/support/modules_libs/java.base/server/libjvm.so
@$BUILDDIR/hotspot/variant-server/libjvm/objs/_BUILD_LIBJVM_objectfilenames.txt
-lm -ldl -lpthread; done)
--- bfd ---
/usr/bin/g++ -fuse-ld=$linker -Wl,--hash-style=both -Wl,-z,defs
-Wl,-O1 -m6 1.31s user 0.36s system 99% cpu 1.669 total
--- gold ---
/usr/bin/g++ -fuse-ld=$linker -Wl,--hash-style=both -Wl,-z,defs
-Wl,-O1 -m6 0.42s user 0.11s system 99% cpu 0.537 total
--- lld ---
/usr/bin/g++ -fuse-ld=$linker -Wl,--hash-style=both -Wl,-z,defs
-Wl,-O1 -m6 0.25s user 0.20s system 145% cpu 0.310 total
Do the constituent object files have debugging information? Sub-second
processing times for ~350 MiB of output are rather impressive.
Ah! That must be it. I just tried with --with-native-debug-symbols=none
and then I get comparable link times.
/Erik
On a Sandybridge-era Xeon (probably without SSD storage), I see a change
from 13 seconds to 8 seconds (BFD to gold). This is the first libjvm.so
link from “make images”, and the output includes (apparently full)
debugging information.
Thanks,
Florian
