| Message ID | 20230523165502.2592-5-jszhang@kernel.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/tree_selection | fail | Failed to apply to next/pending-fixes, riscv/for-next or riscv/master |
On 2023/5/24 0:55, Jisheng Zhang wrote: > From: Zhangjin Wu <falcon@tinylab.org> > > Select CONFIG_HAVE_LD_DEAD_CODE_DATA_ELIMINATION for RISC-V, allowing > the user to enable dead code elimination. In order for this to work, > ensure that we keep the alternative table by annotating them with KEEP. > > This boots well on qemu with both rv32_defconfig & rv64 defconfig, but > it only shrinks their builds by ~1%, a smaller config is thereforce > customized to test this feature: > > | rv32 | rv64 > --------|------------------------|--------------------- > No DCE | 4460684 | 4893488 > DCE | 3986716 | 4376400 > Shrink | 473968 (~10.6%) | 517088 (~10.5%) > > The config used above only reserves necessary options to boot on qemu > with serial console, more like the size-critical embedded scenes: > > - rv64 config: https://pastebin.com/crz82T0s > - rv32 config: rv64 config + 32-bit.config > > Here is Jisheng's original commit-msg: > When trying to run linux with various opensource riscv core on > resource limited FPGA platforms, for example, those FPGAs with less > than 16MB SDRAM, I want to save mem as much as possible. One of the > major technologies is kernel size optimizations, I found that riscv > does not currently support HAVE_LD_DEAD_CODE_DATA_ELIMINATION, which > passes -fdata-sections, -ffunction-sections to CFLAGS and passes the > --gc-sections flag to the linker. > > This not only benefits my case on FPGA but also benefits defconfigs. > Here are some notable improvements from enabling this with defconfigs: > > nommu_k210_defconfig: > text data bss dec hex > 1112009 410288 59837 1582134 182436 before > 962838 376656 51285 1390779 1538bb after > > rv32_defconfig: > text data bss dec hex > 8804455 2816544 290577 11911576 b5c198 before > 8692295 2779872 288977 11761144 b375f8 after > > defconfig: > text data bss dec hex > 9438267 3391332 485333 13314932 cb2b74 before > 9285914 3350052 483349 13119315 c82f53 after > > Signed-off-by: Zhangjin Wu <falcon@tinylab.org> > Co-developed-by: Jisheng Zhang <jszhang@kernel.org> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > Reviewed-by: Guo Ren <guoren@kernel.org> > Tested-by: Bin Meng <bmeng@tinylab.org> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> > --- > arch/riscv/Kconfig | 1 + > arch/riscv/kernel/vmlinux.lds.S | 6 +++--- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 8f55aa4aae34..62e84fee2cfd 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -115,6 +115,7 @@ config RISCV > select HAVE_KPROBES if !XIP_KERNEL > select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL > select HAVE_KRETPROBES if !XIP_KERNEL > + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION > select HAVE_MOVE_PMD > select HAVE_MOVE_PUD > select HAVE_PCI > diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S > index e5f9f4677bbf..492dd4b8f3d6 100644 > --- a/arch/riscv/kernel/vmlinux.lds.S > +++ b/arch/riscv/kernel/vmlinux.lds.S > @@ -85,11 +85,11 @@ SECTIONS > INIT_DATA_SECTION(16) > > .init.pi : { > - *(.init.pi*) > + KEEP(*(.init.pi*)) > } > > .init.bss : { > - *(.init.bss) /* from the EFI stub */ > + KEEP(*(.init.bss*)) /* from the EFI stub */ > } > .exit.data : > { > @@ -112,7 +112,7 @@ SECTIONS > . = ALIGN(8); > .alternative : { > __alt_start = .; > - *(.alternative) > + KEEP(*(.alternative)) > __alt_end = .; > } > __init_end = .;
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 8f55aa4aae34..62e84fee2cfd 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -115,6 +115,7 @@ config RISCV select HAVE_KPROBES if !XIP_KERNEL select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL select HAVE_KRETPROBES if !XIP_KERNEL + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION select HAVE_MOVE_PMD select HAVE_MOVE_PUD select HAVE_PCI diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S index e5f9f4677bbf..492dd4b8f3d6 100644 --- a/arch/riscv/kernel/vmlinux.lds.S +++ b/arch/riscv/kernel/vmlinux.lds.S @@ -85,11 +85,11 @@ SECTIONS INIT_DATA_SECTION(16) .init.pi : { - *(.init.pi*) + KEEP(*(.init.pi*)) } .init.bss : { - *(.init.bss) /* from the EFI stub */ + KEEP(*(.init.bss*)) /* from the EFI stub */ } .exit.data : { @@ -112,7 +112,7 @@ SECTIONS . = ALIGN(8); .alternative : { __alt_start = .; - *(.alternative) + KEEP(*(.alternative)) __alt_end = .; } __init_end = .;