From b6254ced4da6cf28d49fbffe24ee4b3286dcb3f4 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 18 Aug 2020 17:19:17 +0000 Subject: powerpc/signal: Don't manage floating point regs when no FPU There is no point in copying floating point regs when there is no FPU and MATH_EMULATION is not selected. Create a new CONFIG_PPC_FPU_REGS bool that is selected by CONFIG_MATH_EMULATION and CONFIG_PPC_FPU, and use it to opt out everything related to fp_state in thread_struct. The asm const used only by fpu.S are opted out with CONFIG_PPC_FPU as fpu.S build is conditionnal to CONFIG_PPC_FPU. The following app spends approx 8.1 seconds system time on an 8xx without the patch, and 7.0 seconds with the patch (13.5% reduction). On an 832x, it spends approx 2.6 seconds system time without the patch and 2.1 seconds with the patch (19% reduction). void sigusr1(int sig) { } int main(int argc, char **argv) { int i = 100000; signal(SIGUSR1, sigusr1); for (;i--;) raise(SIGUSR1); exit(0); } Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/7569070083e6cd5b279bb5023da601aba3c06f3c.1597770847.git.christophe.leroy@csgroup.eu --- arch/powerpc/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/powerpc/Kconfig') diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index aad8532a718e..8d12da224cb9 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -422,6 +422,7 @@ config HUGETLB_PAGE_SIZE_VARIABLE config MATH_EMULATION bool "Math emulation" depends on 4xx || PPC_8xx || PPC_MPC832x || BOOKE + select PPC_FPU_REGS help Some PowerPC chips designed for embedded applications do not have a floating-point unit and therefore do not implement the -- cgit v1.2.3