(Sending as RFC due to the note below.) The Thumb-2 instruction set generates denser code, allowing for more efficient use of the cache and consequently higher execution performance.
Vmlinux (uncompressed) size comparison for my personal configuration (Linux 5.4.46, compiled with gcc 9.3.0 and binutils 2.34): Pure ARM: 24243392 bytes Thumb-2: 22102716 bytes NOTE: This requires enabling a linker bug workaround to avoid the emission of R_ARM_THM_JUMP11 relocations [1] in modules, which the kernel doesn't support. Since this effectively implies -fno-optimize-sibling-calls [2], we're generating suboptimal code. While compat (and in-tree) modules load and run correctly without this workaround, WireGuard fails to load with an unknown relocation 102 error. [1] https://static.docs.arm.com/ihi0044/e/IHI0044E_aaelf.pdf (page 28) [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/arm/Makefile?h=linux-5.4.y#n129 Signed-off-by: Rui Salvaterra <rsalvate...@gmail.com> --- target/linux/mvebu/cortexa9/config-5.4 | 2 ++ 1 file changed, 2 insertions(+) create mode 100644 target/linux/mvebu/cortexa9/config-5.4 diff --git a/target/linux/mvebu/cortexa9/config-5.4 b/target/linux/mvebu/cortexa9/config-5.4 new file mode 100644 index 0000000000..6aff77fda7 --- /dev/null +++ b/target/linux/mvebu/cortexa9/config-5.4 @@ -0,0 +1,2 @@ +CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11=y +CONFIG_THUMB2_KERNEL=y -- 2.27.0 _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel
